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Fluoroalcohols—XX
Spe~trochlmk8 Acta,Vol. 2OA,pp. 1121to 1157.PergamonPress1078.Printedin NorthernIreland
Fluoroalcohob-XX. Infrared and &man spectra of hexafluoro-2-propanol and its deuterated analogues JUEANI MURTO, AIXTTI KIXNEN*, REA VIITAU and JOUKOHYGMXKI Department of Physical Chemistry, University of Helsinki, Meritulhnkatu 1, Helsinki 17, Finland (Received 6 Sqtcmber
1972)
Abstract-The infrared speotra of hexafluoro-2-propanol and its three deuterated analogues in the gaseous, liquid and solid states and the Raman spectra of the compounds in the liquid state were recorded. Assignments of the vibration bands are made, and especiallythe vibrations related to the OH and OD groups are discussed. Two bands due to 0, and C, conformers are found in the OH stretching region; several pairs of suni and difference bands related to the lower-frequenoy (C6) band are seen in the vapour spectra. Association “fingers” occur in the spectra of the condensed phases between 2600 and 2900 cm-l. Two association bands due to in-plane OH bending were found in the spectra of (CFs).&HOH. No associationband due to OH torsion was found with certainty in the liquid phase spectra of any of the oompounds.
discussed in previous papers [I, 21 the OH stretching vibration of l,l,l,33%hexafluoro-2-propanol (HPP) in carbon tetrachloride. The present paper deals with the OH stretching and other vibrations of this compound and its deuterated anrtlogues (CF,),CHOD (HFP-OD), (CF,),CDOH (HFP-CD) and (CF,),CDOD (HFP-d,) in the gaseous, liquid and solid states. A study of these compounds in argon, nitrogen and carbon monoxide m&rices has been carried out [3]. Infrared spectra of the compounds in carbon tetrachloride, carbon disulphide and benzene and their Raman spectra in carbon tetrachloride, water and dimethyl sulphoxide have been recorded. Only the most important results concerning the solution spectra are discussed in the present paper; details will be published elsewhere [a]. Normal coordinate calculations based on dstta reported in the present paper are in progress in our laboratory [6]. Papers have been published on the ape&a of the related compounds (CFs),C=O 16, 71, (CF,),CF2 171, PU,WH,h PI, (CF,),C=~ 191, (CFJ,C=c---o [Ql, (CF,),C=N=N [Q] and (CF,),POH [lo]. We have reported results for the WE HAVE
* Department of Pharmacy, University of Helsinki, Helsinki 17, Finland [I] [2] [3] [4] [S] [S] [7] [8] [9] [lo]
A. KIVLNEN and J. MURK, Swnner,Kenaist&hti 4OB, 6 (1967). J. MURTO and A. RIVINIEN,SWJHW~K~~~~~~~~~~~~~~B, 14 (1967). A. J. BARNESand J. MURTO, J. Chmn.Sm. Fcwaday1188, 1642 (1972). J. Mrrrt~o,A. KlvINEN, M. N&&xx&r& R. V~~~AI,Aand J. HY&&KI, Suomen KemktiZeirti 46B (1973) in press (Part XIX). M. PERTJXLA, to be published. C. V. BERNIEY, Speetrochim. Acta 21, 1809 (1966). E. L. PACE, A. C. FLAUSCH and H. V. SD ON, +ecZrockim. Aota $@, 998 (1966). K. E. BLICXC,F. C. NAEM and K. NIEDENZTJ, Spectmhiwa. Actu 27A, 777 (1971). F. A. MILLER and F. E. &VIAT, Spectrochim.Acta %A, 1577 (1969). R. C. DOBBIE and B. P. STRAWGHAN, Spectroohim. Aoto 27A, 266 (1971). 1121
1122
Jm
MURTO, ANTTI KNINEN,
perhalogenerated tertiary (CF,),COH (PFTB) [12].
butyl
REA VITTALA and JOUKO HYSUEI
alcohols
(CF,),CCI,OH
(TCHFB)
[ll]
and
EXPERIMENTAL HFP was purified by fractional distillation [13]. The deuterated alcohols were synthesized as described previously [3]. The lsF NMR spectrum of HFP-CD contained only a singlet band at 77.03 ppm from CFCl, (CFCI,CF,Cl as an internal standard). The product contained about 1 per cent of HFP as deduced from its i.r. spectrum. The lsF NMR spectrum of HFP showed a doublet at 7690 and 7699 ppm (JHF = 6 Hz, similarly as in the proton spectrum [14]). The i.r. spectra were measured with 8 Perkin-Elmer 621 spectrometer as previously [ll]. The frequency scale of the spectrometer was calibrated frequently with the aid of atmospheric water and carbon dioxide. The gas spectra were recorded using a 10 cm gas cell with cemented KBr windows, a 1 m gas cell with CsI windows or a 5 cm variable temperature gas cell with KBr windows. The cells were fllled to the desired pressure with the aid of a vacuum line. Some low-frequency gas spectra were recorded with a Perk&Elmer 180 spectrometer using a 10 cm cell with polythene windows. Spectra of liquids were taken employing sealed cells FH-OlK (from RIIC), and the spectra of the solids employing a variable temperature unit VLT-2 (RIIC) and NaCl windows. The cell containing the liquid was cooled with a mixture of dry ice and acetone or with liquid nitrogen. A sodium asbestos cartridge was required to remove atmospheric carbon dioxide, the bending vibration of which has a sharp Q-branch at about 670 cm-l, in the air drying unit when the 670 cm-r bands of the CD deuterated alcohols were recorded. The Raman spectra were taken with a JarrehAsh 25-305 spectrometer equipped with an Orlando Ar/Kr ion laser. The exciting line used was the 488 nm line; its intensity at the sample was about 200 mW. A Per&in-Elmer multipass cell was used for most of the measurements. The spectral slit width (about 2 cm-l) was held constant by a slit servo system. The alcohols showed considerable fluorescence background, which diminished on repeated distillation of the alcohols. The positions of sharp i.r. and Raman bands are believed to be accurate to &2 cm-l. The non-S1 units used are 1 A = lo-lo m and 1 amu = 1.660 x l(r% g. RESETS
AND D~suuss~o~
The HFP molecule should possess 30 fundamental modes of vibration, of which 11 are stretching, 16 deformation and 3 torsion vibrations. If the rotations around the C-C and C-O bonds are relatively free, the point group is C,; this is usually assumed in studies dealing with 2-propanol [15, 161and also other alcohols (see also Ref. [9] concerning compounds that contain the (CF,),C group). Of the vibrations, 17 should be of species a’ and 13 of species a”. All vibrations should be active in both ix. and Raman. The principal moments of inertia were computed by a programme written by SCHACHTSCHNEIDER [17] employing the structural parameter values used in the [ll]
J. MURTO,A. KWINE N, K.
KAJANDER,
J. HySmXxr and J. KORPPI-TOMZ~OL~,Aota them.
Stand., in press.
[12] J. MURTO, A. KMNEN, J. KORPPI-TOMMOLA, R. VIITAL~ and J. Hyijtixr, Acta Chem. &and., in press. [13] J. MTJRTO,A. KI~INEN, S. K~~IMAA and R. LAAICSO,Sucmen Kemiet&hti 4OB, 260 (1967). [14] J. MURTO, A. KIVINEN and L. STRANGE, Suomcn Kem&iZehti 44B, 308 (1971). [15] C. TAN-, N@po” Kagaku Zaahi 83, 621, 661 (1962). [16] L. I. LAKER, B. I. JA~EBSON and G. A. KORAN, Izw. Akad. Nauk SSSR, Ser. Khim. 8, 1717 (1969). [17] J. H. SOIXACHTSCHNEIDER, Tech. Report No. 231-64, Shell Development Co. (1964).
Infrared and Reman
spectra of hexafluoro-Z-propanol
1123
study of PFTB [12].The following values were obtained for HFP: JA = 239, IB = 451 and I, = 515 amu AZ. The values refer to the C, conformer shown in Fig. 1. Two principal rtxes of inertia are in the symmetry plane, and the third, the A axis, is perpendicular to this plane. The C a.xisis almost parallel to the C-H bond and the centre of mass is close to the line joining carbons C, and C,. The values of the moments of inertia imply that the molecule is an almost prolate symmetric top. The BADOER-ZUMWALT parameters [18] for HFP are S = -0.74, p = 0.98, i.e. nearly the same as for hexafluoroacetone [6].In both cases, i.r. bands of the vapour due to vibrations where the change of dipole moment is parallel to the A axis should have the P&R structure characteristic of parallel bands in symmetric top molecules. For the P - R separation AY(P - R) of such bands the formulae of GERHARDand DENNISON[19] give a value of about 10 cm-l at ambient temperature.
I(C,)
II
Fig. 1. The two main conformers of HFP.
In the vapour i.r. spectrum of HFP, there are three bands, at 1117, 689 and 350 cm-i, with a clear P&R type struoture, Av(P - R) being about 9 cm-l in each case. The band at about 1117 cm-l is missing in the spectrum of HFP-CD, and there is an A-type band at 1028 cm-l (A@’ - R) about 9 cm-l). Bands with apoorlyresolved P&R structure are found at 1379 and 894 cm-l in the vapour spectrum of HFP. There are two bands in the vapour spectrum of HFP at about 535 end 550 cm-l that partly overlap. It seems probable that one or both of them are type-B bands, Av(Q-Q) being4-5 cm- l. HFP-CD has a B-type band with peaks at 643 and 648 cm-l, Only one C-type band was found, at 738 cm-l, in the vapour spectrum of HFP. The asymmetry parameters of UEDA and SHIMANOUCHI [20] for HFP are 2 = l-75, y = -0-338. We can deduce from the figures published by these authors that a 1: 1 B/C hybrid band of HFP would be triangular and that a C-band would be similar to that found st 738 cm-i (Fig. 2). There are indeed triangular bands at 1205, 833 and 514 cm-l, possibly also at 3626 end 1244 cm-l, in the spectrum of gaseous HFP (Figs. 2 and 3). Some bands, such as the OH and CH stretching bands, are doublets, obviously because of conformational heterogeneity and intramolecular interactions [2, 3, 211. [18] R. M. BADQER and L. R. ZUMWALT, J. Chm. Phya. 6, 711 (1938). [I91 5. L. GERHARD and D. M. DENNISON, Phya. Rev. 43,197 (1933); W. A. SETH PAUL and G. DIJKSTRA, S~ecbrochint. Acta 23A, 2861 (1967). [ZO] T. UEDA and T. SHIMANOUCHI, J. Mol. Spectry 28, 350 (1968). [21] K. F. PURCELL, J. A. STIKELEATEER and S. D. BRUNK, J. Mol. Spectry 32, 202 (1969).
1124
JUEANI MURTO, AWCCI KIVINEN, REA VIITALA and Jowo
3700
I
3600
I
I
900 cm-’
HYGMXICI
I
I
so0 I
700
Fig. 2. Band contours in i.r. spectra of HFP vapour. The 6 cm cell was cooled with dry ice in a polythene bag. A, pressure 26 mmHg; B, pressure IS mmHg (at room temperature).
3700 36003OoO2900
1400
1200
1000
so0
600
600
400
300
cm-l Fig. 3. 1.r. spectrum of gaseous HFP. A, 10 om cell, pressure 4 mmHg; cell, pressure 6 mmHg.
B, 1 m
Also splitting of the skeletal and CF stretching bands into doublets was observed in the spectra of HFP in nitrogen and carbon monoxide matrices [3]. It is obvious that the presence of bands due to two conformers complicates the band envelopes. Thus, for example, the band at 460 cm-l consists of two weakly separated maxima 3-4 cm-l apart, and the envelope might be that of two narrow triangular bands that have shifted slightly apart. The same may apply also to the band at 327 cm-l. About ten of the bands (for each alcohol studied) were completely or almost completely depolarized, which indicates that the molecules have symmetry. The lowest depolarization ratios (ca. 0.04) were found for symmetric skeletal stretchings. Vapour spectra of HFP were recorded also at temperatures up to 200°, but no marked changes were noted (except broadening of the bands and a shift of the band at 3666 cm-l that is discussed below).
Infraredand Raman spectra of hexafluoro-2-propanol
1125
The ~e~~~ dwve 1500 OX+ OH (OD) stretching. The YOH doublet is at 3666 and 3626 cm-l in the spectrum of gaseous HPP (Fig. 2). As mentioned above, the doublet character of the OH stretching band is due to conformational heterogeneity and intramolecular interactions. In the matrix isolation study [3] it was found that the lower-frequency band is really a doublet due to two conformers in nitrogen and carbon monoxide matrices and that there are thus three different conformers. No band due to the C, conformer was seen in the spectrum of HFP in an argon matrix [3].
5i--- 2900
I
1400
,
I,
I,
1200
IO00
I,
800
I
600
I,
I
400
200
cm+
Fig. 4. Barnan epeotrum of liquid EFP excluding the OH stretching region.
If the temperature of the HFP vapour is varied, the sharp peak at 3626 cm-l remains fixed but the broader, smaller peak at 3666 cm-l shifts to higher frequencies with decreasing temperature at a rate of -0*026 cm-l K-l; this shift has been noted also by MILLEN [22]. The envelope of the vOH (or YOD) doublet was very similar in the vapour spectra of all four isotopically different alcohols. The peaks are at 2704 and 2675 cm-l in the spectrum of HFP-OD vapour, the ratio YOH/YOD being thus 1.35. Doublets (due to terminal OH (Of)) groups or to monomers) are seen as shoulders on the broad polymer bands in the i.r. and Raman spectra of the neat liquids Figs. 5(b) and 5(c)]. The bands are doublets also in the spectra of carbon tetrachloride solutions. The maxima are at 3615 and 3578 cm-l in the case of HFP [Z, 41; the relative intensities of the two peaks are the reverse of those in the vapour spectrum. The enthalpy difference between the two conformers in carbon ~trac~oride is 0.6 kJ mol-r[2], whereas it is 4.6 kJ mol-l in the vapour [22]. Thus, carbon tetrachloride seems to stabilize the higher-energy conformer, similarly as do the nitrogen and carbon monoxide matrices. The doublet splitting is still more marked in spectra of solutions of HFP in hexafluorobenzene; no splitting is seen in spectra of benzene solutions [4], The two OH stretching peaks of WFP differ with regard to anharmo~city in carbon tetrachloride; the anharmonicity constant is 82 cm-i for the C, and 62 cm-i for the C, conformer [4]. It is about 50 cm-l for both conformers in the vapour. 1221 13. J. MILLEN,Private coxnmunication.
1126
JUHANIMUR~O, ANYCI KIVINEN, REA VIITALA and JOTJKO HY~WUI
I
4000 cm-1 Fig. 5(a). The OH stretching region in the ix. spectrum of HFP vapour in a 1 m cell, pressure 95 GnHg.
1
I----
t
s 6
z E z
z 400
I
3500
I
I
3000
3500
cm-1 Fig. 6(b). The OH stretching region in the i.r. spectrum of liquid HFP, KBr windows, cell thickness O-02mm.
The two main conformers are obviously those shown in Fig. 1. The higherfrequency band has been assigned to the “free” conformer (C,) [2, 31. It may be mentioned that the i.r. spectrum of gaseous l,l,l-trifluoro-2-propanol shows only one YOH peak (at 3651 cm-r) [23], and so does also the spectrum of S-phenyl-hexafluoro-2-propanol (the peak is at 3628 cm-l). [23] J. MTJRTO, A. KMNEN and K. EDELMAN,unpublishedresults.
Infrared and Raman spectra of hexafluoro-2-propanol
3600
3400
3200
3000
2600
2600
1127
2400
cm-1 Fig. 5(c). The OH and OD stretching regions in the Raman spectra of liquid HFP (A) and liquid HFP-OD (B).
cm-l Fig. 5(d). The OH stretching region in the i.r. spectra of solid HFP (C) and solid HFP-CD (D). Cell thickness 0.025 mm, temperature -190“.
There occur sum and difference bands of the OH stretching vibration and several low-frequency fundamentals in the vapour spectra Fig. 5(a)], and these relate to the lower-frequency OH stretching peak only. The most intense combination bands of this type in the spectrum of HFP are at 3626 f 329 cm-l (due to G-C-C bending), 3626 + 287 cm-l (due to OH torsion) and 3626 f 248 cm-l (due to CF, rocking). The only intense combinations in the vapour spectrum of PFTB were YOH -& TOH [12], which were relatively more intense than the corresponding bands
1128
JVEAXIMUXWO, AX!~TIKIVINEN, REA VIITAL~Land JOWEO EY~MXEI
in the spectrum of HFP. If water is present in HFP vapour, a broad HFP-H,O complex is seen at 3450-3500 cm-l [24]. A marked ~sociation band of the OH stretch~g is seen in the i.r. and Raman spectra of the liquids [Figs. 5(b) and 5(c)], although the tendency of HFP to associate is considerably weaker than that of 2-propanol [l, 31. The association band is broad and featureless, also in the Raman spectrum obtained after turning the analyzer 90’ (marked 1. in the figures). The vOH ~ociation bands of nonhalogena~d alcohols show two maxima in the 1 spectra [25]; the minimum between them obviously corresponds to some symmetric associate structure. Only a broad polymer band is seen in the spectra of the solid alcohols in the OH stretching region [Fig. 5(d)]. Sometimes, however, the band has a shoulder and there are small differences also in the CF stretching region. The crystal form may thus have been different when the different spectra were recorded (cf. [.26]). There were three “fingers,” at 2890, 2760 and 2640 cm-r, in the spectrum of solid HFP [Fig. 5(d)] that were weaker in the spectrum of liquid HFP and almost absent from the spectrum of the vapour. Similar bands are seen in the spectrum of solid phenol [27]. The most probable explanation is that they are due to overtones and combinations of the two OH bending association bands and possibly also of the CH bending band at 1380 om- l; these “borrow” intensity from the vOH association band. The association band occurs at lower frequencies in the solid state than in the liquid state, and thus the fingers are most intense in the spectra of the solids. Only two fingers of marked intensity are seen in the spectrum of solid HFP-CD [Fig. 5(d)] (note that there are no CH vibrations in this compound). HFP-dB has only one finger (at 2165 cm-l), and so obviously has also HFP-OD (at 2035 cm-l). CH (CD) stretching. The rCH band of HFP is also a doublet in the spectrum of the vapour (peaks at 2984 and 2943 cm-l) and of the carbon tetrac~o~de solution [a], but not in the spectrum of the neat liquid or the solid. Also in this case the intensity ratio is reversed when going from the vapour to the Ccl, solution. Both peaks are round and featureless in the vapour spectrum. The peak at 2984 cm-l in the vapour spectrum is more intense than that at 2943 cm-l, and thus we consider the former peak to correspond to the C, conformer. It is difficult to identify the CD stretching band in the i.r. spectra of CD deuterated fluoroalcohols as it is inherently weaker than the CH stretching band and is situated in the region of the overtones of the intense CF stretching bands. The doublet is most clearly seen in the spectrum of HFP-CD in carbon tetrachloride (peaks at 2 188 and 2165 cm-1 [a]). The CD stretching band is intense in the Raman spectra and is at about 2200 cm-l. The CH stretching band is a doublet also in the spectra of 2-propanol. This has been attributed 1283to ~~ra~tion between the C--H bond and the lone electron pair of oxygen. [24] M. A. HUSSEIN, D. J. MILLEN and G. W. M&ES, Chm. Commun. 172 (1970). [26] J. MURTO and A. KXVLNEN,unpublislmd results. [.26] J. MURTO,A. KIVIHENand K. HAXSTE, de& Chmz. Smnd. 24,3057 (1970). [27] J. C. EVANS, S~e&rochim.dcta IS, 1382 (1960). [28] P. J. KRTJE~ER,J. JAN and H. WIESER,J. Mol. Struct. 5, 375 (1970).
Infraredand Ramsn spectraof hexafluoro-2-propenol
1129
The region 1500-1100 (1600-900) cm-l In this region we expect to find six CF stretchings (3~’ + 3a”), an OH in-plane bending and two CH bendings (a’ + a”). The CF stretching bands are very intense and mask other, weaker bands, and also, because of coupling effects, the positions and intensities of bands may be different from those for other alcohols. Thus the band assignments based on group frequencies can be only very approximate at best (cf. [29, 30-j). In the assignment we rely in many respects on the matrix isolation study [3]. OH (OD) in-plane bending. The 60H vibration of alkanols has been discussed in several papers [31--331. Because of heavy coupling of this vibration with other vibrations, there are usually several bands in the spectrum that can be ascribed to OH bending [31, 321. The bands at 1311 (HFP), 1004 (HFP-OD), 1328 (HFP-CD) and 1067 cm-l (HFP-d,) in the spectra of argon matrices [3] were ascribed to OH (OD) bending; these were all relatively strong bands. The corresponding bands in the vapour spectra are at 1308, 1000, 1318 and 1069 cm-l, respectively. The position of about 1300 cm-l seems well founded for the OH bending band because the band is at 1250 cm-l in the spectrum of gaseous 2-propanol [El, and it shifts to higher frequencies almost linearly as the number of fluorine atoms increases in fluorinated tertiary butyl alcohols [12,34] (the frequency increases from 1330 cm-l in the spectrum of t-butyl alcohol to 1381 cm-l in the spectrum of PFTB). Although the intensities of the OH bending bands of hexafluoro-2-propanols mentioned above undergo no marked changes on going from vapour to liquid to solid, there is considerable evidence in favour of the assignments (Tables l-4), viz., the matrix isolation spectra [3], analogy with fluorinated butanols [12, 341 and the positions of the overtones (fingers). The band at 937 cm-l in the spectrum of HFPCD disappears on going from the vapour to the solid, but this frequency is too low for an OH bending band (the band may, however, have some 80H or 70H character). The reason for the insensitivity of the OH bending to change of phase and for its high intensity must be its coupling with other vibrations. There is a broad association band at 1425 cm-l in the i.r. and Raman spectra of liquid HFP. There is a polarized band at 1310 cm-l in the Raman spectrum of liquid HFP; in the spectra of aqueous mixtures [4], this band is broader and at about 1340 cm-l (the band at 1290 cm-l has not moved) and the band at 1425 cm-l has shifted to 1455 cm-l. Both of these bands are absent from spectra of liquid HFP-OD and are obviously association bands. The band at 1430 cm-l in the i.r. spectrum of solid HFP-CD is with certainty and the band at 1348 cm-l probably an association band. CH (CD) bendinga. Although the in-plane (a’) CH bending usually occurs at a higher frequency than the out-of-plane (a”) bending [15, 351, this order is reversed [29] E.
C. TUAZON, W. G. FATELEY and F. F. BENTLEY, AppZ. &e&y a, 374 (1971). H. F. SEURVELL and J. T. BULUEB, J. FZuor. Ohem. 1, 391 (1971/72). A. V. STUART and G. B. B. M. SW, J. C?mn. Phye. 24, 669 (1966). S. Km&f& C. Y. LIAXU and G. B. B. M. SUTHE~AND, J. Chem. Phys. 25, 778 (1956). P. TARTE and R. DEPONTH&RE, J. Chmn. Phya. a6, 902 (1957); BuU. Soo. C&a. Be&m 66, 626 (1957). [34] J. KORPPI-TOMMOLA, unpublished results. [35] C. V. BERNEY, Spectrochim.Acta 25A, 793 (1969).
[30] [31] [32] [33]
1130
JUEAN-I MURTO,
ANTTI
KIVINEN,
VIITALA and Jowo
REA
HYGMXEI
Table 1. The observed i.r. and Raman frequencies (cm-l) for (CF,),CHOH the region 2600-1500 cm-l) vapour i.r.*t 7240 7160 3964 3912 3873 3666 3630 3626
Liquid RWWIl$
Liquid i.r.
“VW vvw vvw VW VW
2670 vvw 2603 ww 1415 w 1379, A? 1360 sh 1308 v8 1273 s
2966 VW > 2876 vvw 2760 vvw
P
2968 (~26)
2616 vvw 1427 w
1425 (2)
1379 1360 1310 1289
1380 1360 1310 1290
8 sh sh, vvw “8
3260 br, s**
P
(4) (
P
0.2
P DP 0.8 DP P P 0.3
1258 s
1260
DP
1263 B 1 1244 WB 1227 sh
1233 VB 1220 V8
1236 12201
DP
1205 ““B B/C
1188 vvs
1194 (4)
DP 0.8
(-1135) 1122 sh 1117~~s A 1113 sh 1 1070 sh 1016 sh 983 vvw 894 m A? 833 m B/C 738m 0 693 689 s A 684 1 610 vvw 670 664 Br 548 1 * 637 632 I w B1 620 sh 614~ B/C 460 466
Assignments 11 2 X 3666 2 x 3626 3626 + 327 3626 + 287 3626 + ~248 a’vOH, 0, conformer
vvw ““TV VW vvw “VW w sh7 m 3630 sh 3592 sh 3430 br, m
3377 3336 3296 2984 2943
Solid i.r. (-75’)
(excluding
1128 (7) 1108 VVB
1108 (7)
P <
0.3
NDP 0.7
2980 VW 2890 2760 2665 2640 1452 1429 1378
w w VW VW m VW VB
1338 w 1292 “8 1260 sh 1254 shtt 1246 vs 1222 “8 1200 B 1186 WB 1179 “VB 1161 sh 1118 vvs 1106 vvs
a’vOH, C, conformer > terminal vOH, 0, conf. terminal vOH, C, conf. yOH, associated 3626 - ~248 3626 - 287 3626 - 327 a’vCH, C, conformer a’vCH, 0, conformer 2 x 1427 2 x 1379 1268 + 1379 2 x 1310 a’ 60H, assooiated 2 x 738 a” 6CH 2 x 688 a’60H. associated a’60H. o’vCF, a’ 8CH a” vCF, a’vCF, > 2 x 610 abvCF, > 327 + 333
a’vCFs
a”vCF,
7418
327 + 738 2 x 614 460 + 614 a” vcc a’vC0, msocktted a’ vco a’vCC
686 “8
a” 8CF,
636 br, mtt 610 m
TOH, associated? a’ 6CF, 1308 - 738
DP
548 VW
a” 6CF,
536 (6)
DP 0.7
532 w
617 w
519 (11)
P 0.5
460 w
463 (19)
P 0.2
a"dCF, a'GCF,;1205 a'GCF, a'6CO
895 m 841 m
896 (2) 838 (68)
737 m
739 (100)
686 B
687 (4)
610~~
613 (16)
652 VW
561 (1)
636 w
DP 0.8 P 0.04 P 0.04 DP 0.8
P 0.5
894 v8 847 8
613 TV
1308 -
894
-
688
1131
lkfrtwed and FCaman spectra of hexaftuoro-2-propanol Table 1. (cont.) V8pOW i.r.*t
396 “VW 382 vvw 373 vvw 365 360 w A 346 1 329 326 >m 287 w 232 VW
Liquid i.r.
Solid i.r. ( - 76’)
Liquid Rsman$
Assiientg~ 1135 894 833 -
360 vvw
360 (IS)
327 vw
328 (63)
296 288 262 237
297 (8)
vw sh vvw? vw
244 br(2) 167 (3) 100-120 br (< 1)
DP 0.8
a= &Jo
P 0.2
O’GCC
DP 0.8
P 0.6 P o-2 DP?
738 514 468
ax pUFs d TOH a’ PDF, 6’ pCF, a’ PWS Y (H-bond)7
* The letters A, B and 0 refer to the band type. ah = shoulder. t Overtone btmds were found Jso at 248112 x 1244), 2370(2 x 1206), 2240(2 X 1135), 2208(2 X 1117), 1790(2 x 894) snd ISSO(2 x 833) em-x. $ The spproximete Raman intensities are given in parentheses. P = polarized, DP = depolarized band; the velues after these are the depolarization ratios. 4 v = stretching, 6 = bending, p = rooking, 7 = torsion. 11 The assignment of combination and overtone bands is based on vapour-state frequencies whenever possible. fi Is seen if the oell is cooled below 0”. l * 3230 em-l at - 190°. tt seen only at -WY. $$ BBOcm-* et --190°.
in the case of HFP [3]. The strong band at 1379 cm-l in the v&pour spectrum of HFP displttys some P&R structure and obviously relates to the ~~rnet~c bending. This bsnd disappears on CD deuteration (it is missing also from the spectrum of 2-phenyl-hexafluoro-2-propanol [25]) and is depolarized in the Raman spectrum of liquid HFP. Hexachloro-2-propanol also has a band at about 1380 cm-l, but this is a doublet in cccrbon ~tr&c~o~de solution [25]; the oo~espon~g band of HFP is & singlet. In no spectrum was the sntisymmetric CD bending found, not even in the matrix spectra [3]. The band at 1272 cm-l in the spectrum of HFP in the argon matrix wits assigned to s~rnet~c CH ben~g. We can deduce from the booty and pol&ri~~tiond&a of the Raman spectra that the symmetric band is at 953 cm-l in the spectrum of liquid HFP-CD and at 897 cm-l in the spectrum of liquid HFP-d,. The value of the OD bending band is 69 cm -1 higher for the latter alcohol than for HFP-OD, and we can deduce that the energy levels of symmetric CD bending and OD bending repel each other in HFP-d,. CF &etchings. These bsnds occur usualIy between 1100 and 1400 cm-l and are the strongest ones in the i.r. spectra, but relatively weak in the Raman spectra. The six CF stretching bands of HFP are somewhat similar to those of HFP-OD, but differ in location from those of the CD compounds (Figs, 3 and 6). The frequencies of the vibrations of the CD compounds are similar to those of 2,2-diaminohexafluoropropane [8], a compound with no CH or OH groups.
1132
Jo-
MIJRTO, ANTTI
KIVINEN,
VIITALA and Jouxo
REA
HY~I&&I
Table 2. The most important ix. and Reman bands of (CF&CHOD vepour i.r.
2987
VW
2943VW
Liquid Reman
Liquid i.r.
>
2960VW
2971(N40)
2736 sh
2730 ah
Solid i.r. (- 75’)
P 0.15
2980 w
2704 w 2675 m
1383 1380 1303 1286 1273 1242
sh BI “S vs B/O sh vvs
1216 W8 1142~1 1117 ““8 1000 935 901 896 892 870 840
m sh ah m sh I sh sh
805 w B/U 726 w 692 688 m A 683 I 601 vvw 553 548 > vw 536 531 Iw 513 w B/C 455 451 >w
332 327 Im 265 VW 210 br. w
2680 sh 2651 sh 2540 br, m
2680 eh 2652 sh 2550 br (~10)
1390 sh
1390 sh
P 0.1 P 0.1 P 0.3
DP 0.8
1380 8
1380 (7)
1289 VB
1290 (10)
1260 sh 1236 ah
1264 1237
1205 ““B
1210 (6)
P 0.6
1109 VW
1128 (9) 1109 (9)
P < 0.3 DP 0.8
1004 m
1005 (3)
DP 0.6
894 m
897 (3)
DP 0.8
P 0.5 DP DP?
2430 2400 2035 1396
br. et ah VW “8
Assignment* o’vCH, 0, conformer o/&H, 0, aonformer o’vOD, 0, conformer a’vOD, 0, conformer terminal YOD, C, oonf. terminal vOD, 0, oonf. a’vOD, associated o’vOD, associated 2 x 1025 2 x 726
1378 “B
o” 6CH
1290 s 1284 8 1255 m 1235 sh 1215 V8 1200 ““B 1180s 1123 s 1107 ““B 1025 *
a’ vCFI a’ 6CH a” vCF, cs”vCF* a’ 6OD. aaaocietedl a’ vCFt
893 8
2 x 610 o’vCFI a” vCFI a’ 6OD, aclsocisti a’ 6OD 330 + 600 a” vcc
813 w
813 (63)
P 0.04
845 vvw 826 m
733 m
733 (72)
P 0.05
737 8
330 + 534 330 + 513 a’vC0, esaooiated a’vC0 a’vCC
687 s
688 (4)
684 ws
o” gCF$
610 VW
611 (22)
610 m
a’ SCF,
550
550 (1)
DP
550 VW
o” 6CF,
DP 0.8 P 0.6
535 w
535 (8)
DP 0.8
535 w
a’ dCF,
516 w
515 (16)
P 0.6
515 w
o’ BCF,
455 w
460 (27)
P 0.4
352 w
348 (22)
DP 0.8
326 m
329 (100)
299 sh
298 (11) 239 (3) 167 (3) 90-110 br (1)
P 0.4 DP 0.8 P 0.4 P 0.15 DPP
0’6CO
a” 6CO O’GCC
or ,&F8
,” ,oCFs (i’ pCF, o” TOD a’ pCF, v (D-bond)?
* The Basignment of oombination Rnd overtone benda is based on vapour-state frequencies whenever possible. t Not soon in all spectra.
Infrared and Reman spectra of hexafluoro-2-propanol
1133
Table 3. The most important i.r. and Raman bands of (CF.J,CDOH vapour i.r.
Liquid RlIRlan
Liquid i.r.
Solid i.r. (- 76’)
3668 w 3628 m
1318 vs
3636 sh 3660 sh 3480 br. m
3640 3600 3460 br
P < 0.2 P < 0.2 P < 0.2
2202 (-33) 1390 br (< 1)
P 0.2
1390 w 1314 s
1316 (6)
P 6.4
1223 vv8 1168m 1132 vs
1032 1028 8 A 1023 937 w 880 eh 814 m B/C 735m 0 673 669 s A 664 648 w B 643 1 631 VW 616 sh 612 w 467 454 >w 356 360 w A 346 1 830’ 325 Im
1019 “B
1266 1231 1226 1170 1145 1132 1072
sh sh? (3) (ml) (1) sh (< 1)
1020 (2)
DP? P 0.6 DP P P? DP 0.76
3290 br, st 3230 sht 2844 VW 2716 VW 2185 VW 1430 m$ 1348 “VW 1311 vs 1306 sh 1256 m 1228 VVB 1210 vs 1168 w 1161 sh 1142 ~811 1068 WTV
a’ vOH, C, conformer terminal YOH, C, oonf. terminal YOH, C, aonf. a’ vOH, sssooiated a’ vOH. associated 2 x 1430 2 x 1348 a’ YCD a’ 60H, associated a’60H, associated? a’SOH, a”vCF, 2 x 669
a’VCFs axvCF,
a’vCF, a” vCF* a’vCF,; 328 + 814 1 (FR?j)
960 VW 940 sh 882 VW 816 In 734m
963 (22) 940 sh
P 0.2
1020 va 1010 sh 966 ww
817 (100) 736 (60)
P 0.1 P 0.1
897 VW 820 8 739 m
a’ vcc > a’ 6CD 289 + 669 2 x 456 a’vC0 O’VCC
667 B
660 (6)
DP 0.8
666 B
a” 6CF,
608 VW
611 (13)
P 0.6
604 w
a/&F,
646 VW
646 ah
DP
a” 6CF,
636 vw
638 (6)
DP
614w
516 (9)
P 0.6
ax SCF, a’9CF,? a’SCF*
468 w
463 (18)
P 0.3
a’&0
362 (13)
DP 0.8
330 (48)
P 0.3
296 (6)
DP 0.8
240 (2) 170 (3)
P 0.6 P 0.2
289 w
* t band 2
l
a’ YOH. C, oonformer
1238 WB Al 1177m 1162 “I3
Assignment
a” SC0 a’GCC a’ a’ a’ a’
pCF, TOH pCF, pCF,
The assignment of combination and overtone bands is baaed on vspour-state. frequencies whenever possible. The vOH association band at -100’ was either a doublet with peaka at 3230 and 3166 cm-1 or e single et 3230 cm-‘. 1440 om-l et - 100”. FR denotea Fermi resorunce. t) Thin bend is wan as e shoulder on the band at 1161 cm- if the lower-frequency vOH aesooiation band is miseing.
a’ VOD, 0, a’ YOD. c,
2680 vw 2MO Yw 26150br. m
2650 2560 br (~10)
P P P
2180 vvw
2140 f-35)
P 0.3
1323 (9)
P 0.4
1345 sh
1340 sh
1322 “8
1320 vs
1072 (7)
P > O”3
1325 sh 1318 YS 1283 s 1233 vvs f212 vs 1200 sh 1167 sh 11518 1087 s
1520 (2)
P
1013 vs
1235 br (4)
1240 vvs
DP
1224 vvs 1177 w 1156 B X089 m 1032 1028 s A
1024 I 900m 870 sh, w 799 m 721 m 675 670 a A 665 1 600 vvw 049 841 > W 631 VW 813 w 452 448 I=
1169 sh 1149 va 1068 m 1020 s
>
2460br, 8 2400sht 21652 2165vw I3508 1341ah
1170 br (1)
DP
895 br, w
897 (6)
PO.4
902 VW
802 w 728m
805 (100) 730 (46)
P 0.54 P 0.06
813 m 733 m
665 s
686 fe)
606 VW
613 (17)
544 VW
545 sh
DP
834 w 513w
538 (4) 616 (10)
DP P 0=4
453 w
460 {24f 420 (3) 361 (19) 330 (90) 300 (7) 240 (21 170 f3) 9~12Osb
DP 0.8 PO+4
conformer conform%r
terminal POD, 0, conf. terminal vQD, 0, conf. a’yOD,
associated
Q’YCD 2 x 1087 I >
a” YCF, a’vCFa
a” YGF$ a’&I$ 1 a’&Fa a” vCF, u’60D
a’ YCD 2 x 450 a’vC0 a’vCC
663 s 607 vvw
P 0‘2 P DP P 0.3 DP P
a” 6CO O’GCC a” ,&F, a’ pCF, !a’ pCF, v [D-bond)?
* The assignment of oombinations and overton@@ IS based on vapour-state frequencies whenever possible. t Not seen in all a3pectra.
There are two bands slightly above Xl00 cm-I in the Raman spectra of liquid HFI? and HIV-OD that axe seen also in the ix. speotra of the solids and in the matrix spectra, but not in the ix. spectra af the liquids and of gaseous HFP, These are considered to be two fundamentals. One of these bands is at 1117cm-l in the speotrum of gaseous HFP and obviously masks the other, muah weaker c&‘-type band at about 1135 cm-l. Two sharp peaks are seen at 1283and 1273 OM-1in the vapour spectrum of HPP (Fig, 3). We consider them to be twa different fundamental bands, but they may also be due to Fermi resonance (cf. [36”J)or conformational splitting.
Infrared and Raman spectra of hexafluoro-2-propanol
The region 1100-700
1136
cm-l
In this region there are the three skeletal stretchings (2a’ + a”) that are easily identified. The band at 738 cm-l in the i.r. spectrum of gaseous HFP is of C-type; the band is highly polarized in the Raman spectrum of the liquid. It is the strongest band in the Raman spectrum of HFP and is clearly due to the symmetric C-C-C
L
I
I
1400
I !
I
1000
cm’-’ Fig. 6. The CF stret&ing region in the i.r. spectrum of gaseous HFP-CD, 10 cm cell, pressure 8 mmHg.
stretching. This vibration produces strong, highly polarized bands also in the Raman spectra of hexafluoroacetone, (CF,),C=X=Y type compounds and TCHFB. It is located at 726 cm-l in the spectrum of gaseous HFP-OD. The band at 838 cm-l in the Raman spectrum of HFP is strong and polarized and must represent mainly the CO stretching. In the vapour spectrum it occurs at 833 cm-l and shifts on OD deuteration to 805 cm-l and on CD deuteration to 814 cm-l (vapour values). In the spectrum of HFP-dE,it is found at 799 cm-l. The association band of CO stretching is on the high-frequency side of the monomer band in the spectra of all isotopic HFP’s (cf. also [a]). The band at 894 cm-l in the vapour spectrum of HFP is weak and depolarized in the Reman spectrum and is due to asymmetric G-C-C stretching. In the spectra of the CD deuterated compounds it is located at 1028 cm-l, presumably as a consequence of interaction with the CD out-of-plane bending which is not observed [3], and displays very clearly a P&R structure.
1136
JTJEUNIMURTO, ANITI KIVINEN, REA VIITALA and Jowo
HYZ~MXKI
The region ‘700-300 cm-l
There should be six CF, bendings (3a’ + 3a”) and three skeletal bendings (2a’ + a”) between 700 and 300 cm-l. It is also possible that one of the CF, rockings is above 300 cm-l. The association band of OH torsion should also be in this region. CF bendings. The 6CF, bands are usually between 450 and 750 cm-l. The band of gaseous HFP centred at 688 cm-l shows the P&R structure (Fig. 2); the band is depolarized in the Raman spectrum of the liquid. Slightly above 600 cm-l there is a band in the spectra of all isotopic HFP’s that is very weak in the i.r. spectra and polarized in the Raman spectra. We assign these two vibrations to asymmetric and symmetric combinations, respectively, of the “umbrella” vibrations, as these usually occur at higher frequencies than the other CF bendings [6]. The band of the asymmetric vibration is at about 670 cm-l in the spectra of the CD deuterated compounds. The other CF bending bands occur obviously between 500 and 550 cm-r. The most intense of these is the band at about 515 cm-l (in both the i.r. and Raman spectra). It is possible that the symmetric CO bending vibration contributes to this band. Skeletal bendings. The band at about 330 cm-l is obviously due to the C-C-C bending. It is very strong in the Raman spectra (it is the strongest band in the Reman spectrum of liquid HFP-OD; cf. also [4]) and its frequency seems to vary only relatively little with structure in spectra of compounds of type CF,CCF,, even when the central carbon is spa hybridized [Q]. The other two skeletal bendings can be roughly described as CO in-plane and out-of-plane bendings. There is a depolarized A-band at 350 cm-l in the spectra of the IIFP’s which we ascribe to the latter vibration. The only remaining band still unaccounted for in the 300-700 cm-l region is the band at about 460 cm-l; in the Raman spectra it is relatively intense and polarized. We ascribe this to the CO in-plane bending. The association band at the OH torsion. This band should be characteristically broad and intense. It is seen at about 640 cm-l in the i.r. spectrum of liquid 2propanol, the half-width being about 200 cm-l. The association band is more indeterminate in the i.r. spectrum of liquid l,l,l-trifluoro-2-propanol and is situated between 600 and 700 cm-l [23]. No corresponding band was found in the spectrum of liquid HFP. A much weaker and narrower (half-width 30-40 cm-l) band was found in the i.r. spectrum of solid HFP at 635 cm-l at a temperature of -75’; at -190’ it was at 660 cm-l. It is possible that this band is the association band of OH torsion. The region below 300 cm-l
There should be in this region the torsion band of nonbonded OH groups, four CF, rocking bands (2a’ + 2a”) and two CF, torsion bands (a’ + a”). The CF, torsion bands were found at 48 and 66 cm-l in the i.r. spectrum of hexa5uoroacetone [6]; a 10-m path length cell is required when studying them. Also the frequencies of the hydrogen bonds are below 300 cm-l. Free OH torsion. The TOH band is obviously at 287 cm-l in the vapour spectrum of HFP and at 289 cm-l in the spectrum of HFP-CD. A broad band centered at
1137
Infrared and Raman spectra of hexafluoro-2-propanol
300
200
100
cm-’ Fig. 7. Raman spectrum of the low-frequency region of liquid HFP-OD. speotrum of HFP is very similar in this region.
The
210 cm-l was seen in the i.r. spectrum of gaseous HFP-OD; this is obviously the OD torsion band. CF, rockings. There are three bands in the Reman spectra (at 167, 239 and 298 cm-l in the spectrum of HFP) that very probably are caused by the rocking vibrations pCF, (see also Fig. 4). Those at 167 and 239 cm-l are polarized and are thus due to symmetric vibrations. The fourth band was not found in the vapour spectrum of HFP, but in the spectrum of HFP-OD there was a band at 265 cm-l that might be the fourth rocking band. This is not seen in the vapour spectrum of HFP because of the much stronger, broad OH torsion band. It may be mentioned that bands at 160, 233, 265 and 275 cm-l have been ascribed to CF, rocking vibrations in case of hexafluoroacetone [6]. Hydrogen bond stretchings. These vibrations occur usually between 100 and 200 cm-l in the spectra of alkanols [37]. In the Raman spectra of HFP and its deuterated derivatives, there is indication of a band at about 100-120 cm-l (Fig. 7), which we ascribe (very tentatively) to hydrogen bond stretching. Aclcr+owledge~~ts-For preliminary measurements we are grat&zl to Mr. MAP NXsuX, Ph. Lit. and Mr. JOOKOKORPPI-TOMMOLA, Ph. Lit. We thank also Dr. A. J. BARNES(University Collegeof Swansea,Wales) for helpful discussions,Dr. W. A. THOU (Swansea)for recording the ?F NMR spectra, and Dr. J. KANKAIG (University of Turku, Finllmd) for checking the frequenciesof the low-frequency vapour bands with a Perkin-Elmer 180 spectrometer. We are also grateful to the Finnish State Council for Sciences for research grants. [37] R. F. LAXE and H. W. THOMPSON, Proo. Roy. Sot. 29lA, 469 (1966).
Fluoroalcohob-XX. Infrared and &man spectra of hexafluoro-2-propanol and its deuterated analogues JUEANI MURTO, AIXTTI KIXNEN*, REA VIITAU and JOUKOHYGMXKI Department of Physical Chemistry, University of Helsinki, Meritulhnkatu 1, Helsinki 17, Finland (Received 6 Sqtcmber
1972)
Abstract-The infrared speotra of hexafluoro-2-propanol and its three deuterated analogues in the gaseous, liquid and solid states and the Raman spectra of the compounds in the liquid state were recorded. Assignments of the vibration bands are made, and especiallythe vibrations related to the OH and OD groups are discussed. Two bands due to 0, and C, conformers are found in the OH stretching region; several pairs of suni and difference bands related to the lower-frequenoy (C6) band are seen in the vapour spectra. Association “fingers” occur in the spectra of the condensed phases between 2600 and 2900 cm-l. Two association bands due to in-plane OH bending were found in the spectra of (CFs).&HOH. No associationband due to OH torsion was found with certainty in the liquid phase spectra of any of the oompounds.
discussed in previous papers [I, 21 the OH stretching vibration of l,l,l,33%hexafluoro-2-propanol (HPP) in carbon tetrachloride. The present paper deals with the OH stretching and other vibrations of this compound and its deuterated anrtlogues (CF,),CHOD (HFP-OD), (CF,),CDOH (HFP-CD) and (CF,),CDOD (HFP-d,) in the gaseous, liquid and solid states. A study of these compounds in argon, nitrogen and carbon monoxide m&rices has been carried out [3]. Infrared spectra of the compounds in carbon tetrachloride, carbon disulphide and benzene and their Raman spectra in carbon tetrachloride, water and dimethyl sulphoxide have been recorded. Only the most important results concerning the solution spectra are discussed in the present paper; details will be published elsewhere [a]. Normal coordinate calculations based on dstta reported in the present paper are in progress in our laboratory [6]. Papers have been published on the ape&a of the related compounds (CFs),C=O 16, 71, (CF,),CF2 171, PU,WH,h PI, (CF,),C=~ 191, (CFJ,C=c---o [Ql, (CF,),C=N=N [Q] and (CF,),POH [lo]. We have reported results for the WE HAVE
* Department of Pharmacy, University of Helsinki, Helsinki 17, Finland [I] [2] [3] [4] [S] [S] [7] [8] [9] [lo]
A. KIVLNEN and J. MURK, Swnner,Kenaist&hti 4OB, 6 (1967). J. MURTO and A. RIVINIEN,SWJHW~K~~~~~~~~~~~~~~B, 14 (1967). A. J. BARNESand J. MURTO, J. Chmn.Sm. Fcwaday1188, 1642 (1972). J. Mrrrt~o,A. KlvINEN, M. N&&xx&r& R. V~~~AI,Aand J. HY&&KI, Suomen KemktiZeirti 46B (1973) in press (Part XIX). M. PERTJXLA, to be published. C. V. BERNIEY, Speetrochim. Acta 21, 1809 (1966). E. L. PACE, A. C. FLAUSCH and H. V. SD ON, +ecZrockim. Aota $@, 998 (1966). K. E. BLICXC,F. C. NAEM and K. NIEDENZTJ, Spectmhiwa. Actu 27A, 777 (1971). F. A. MILLER and F. E. &VIAT, Spectrochim.Acta %A, 1577 (1969). R. C. DOBBIE and B. P. STRAWGHAN, Spectroohim. Aoto 27A, 266 (1971). 1121
1122
Jm
MURTO, ANTTI KNINEN,
perhalogenerated tertiary (CF,),COH (PFTB) [12].
butyl
REA VITTALA and JOUKO HYSUEI
alcohols
(CF,),CCI,OH
(TCHFB)
[ll]
and
EXPERIMENTAL HFP was purified by fractional distillation [13]. The deuterated alcohols were synthesized as described previously [3]. The lsF NMR spectrum of HFP-CD contained only a singlet band at 77.03 ppm from CFCl, (CFCI,CF,Cl as an internal standard). The product contained about 1 per cent of HFP as deduced from its i.r. spectrum. The lsF NMR spectrum of HFP showed a doublet at 7690 and 7699 ppm (JHF = 6 Hz, similarly as in the proton spectrum [14]). The i.r. spectra were measured with 8 Perkin-Elmer 621 spectrometer as previously [ll]. The frequency scale of the spectrometer was calibrated frequently with the aid of atmospheric water and carbon dioxide. The gas spectra were recorded using a 10 cm gas cell with cemented KBr windows, a 1 m gas cell with CsI windows or a 5 cm variable temperature gas cell with KBr windows. The cells were fllled to the desired pressure with the aid of a vacuum line. Some low-frequency gas spectra were recorded with a Perk&Elmer 180 spectrometer using a 10 cm cell with polythene windows. Spectra of liquids were taken employing sealed cells FH-OlK (from RIIC), and the spectra of the solids employing a variable temperature unit VLT-2 (RIIC) and NaCl windows. The cell containing the liquid was cooled with a mixture of dry ice and acetone or with liquid nitrogen. A sodium asbestos cartridge was required to remove atmospheric carbon dioxide, the bending vibration of which has a sharp Q-branch at about 670 cm-l, in the air drying unit when the 670 cm-r bands of the CD deuterated alcohols were recorded. The Raman spectra were taken with a JarrehAsh 25-305 spectrometer equipped with an Orlando Ar/Kr ion laser. The exciting line used was the 488 nm line; its intensity at the sample was about 200 mW. A Per&in-Elmer multipass cell was used for most of the measurements. The spectral slit width (about 2 cm-l) was held constant by a slit servo system. The alcohols showed considerable fluorescence background, which diminished on repeated distillation of the alcohols. The positions of sharp i.r. and Raman bands are believed to be accurate to &2 cm-l. The non-S1 units used are 1 A = lo-lo m and 1 amu = 1.660 x l(r% g. RESETS
AND D~suuss~o~
The HFP molecule should possess 30 fundamental modes of vibration, of which 11 are stretching, 16 deformation and 3 torsion vibrations. If the rotations around the C-C and C-O bonds are relatively free, the point group is C,; this is usually assumed in studies dealing with 2-propanol [15, 161and also other alcohols (see also Ref. [9] concerning compounds that contain the (CF,),C group). Of the vibrations, 17 should be of species a’ and 13 of species a”. All vibrations should be active in both ix. and Raman. The principal moments of inertia were computed by a programme written by SCHACHTSCHNEIDER [17] employing the structural parameter values used in the [ll]
J. MURTO,A. KWINE N, K.
KAJANDER,
J. HySmXxr and J. KORPPI-TOMZ~OL~,Aota them.
Stand., in press.
[12] J. MURTO, A. KMNEN, J. KORPPI-TOMMOLA, R. VIITAL~ and J. Hyijtixr, Acta Chem. &and., in press. [13] J. MTJRTO,A. KI~INEN, S. K~~IMAA and R. LAAICSO,Sucmen Kemiet&hti 4OB, 260 (1967). [14] J. MURTO, A. KIVINEN and L. STRANGE, Suomcn Kem&iZehti 44B, 308 (1971). [15] C. TAN-, N@po” Kagaku Zaahi 83, 621, 661 (1962). [16] L. I. LAKER, B. I. JA~EBSON and G. A. KORAN, Izw. Akad. Nauk SSSR, Ser. Khim. 8, 1717 (1969). [17] J. H. SOIXACHTSCHNEIDER, Tech. Report No. 231-64, Shell Development Co. (1964).
Infrared and Reman
spectra of hexafluoro-Z-propanol
1123
study of PFTB [12].The following values were obtained for HFP: JA = 239, IB = 451 and I, = 515 amu AZ. The values refer to the C, conformer shown in Fig. 1. Two principal rtxes of inertia are in the symmetry plane, and the third, the A axis, is perpendicular to this plane. The C a.xisis almost parallel to the C-H bond and the centre of mass is close to the line joining carbons C, and C,. The values of the moments of inertia imply that the molecule is an almost prolate symmetric top. The BADOER-ZUMWALT parameters [18] for HFP are S = -0.74, p = 0.98, i.e. nearly the same as for hexafluoroacetone [6].In both cases, i.r. bands of the vapour due to vibrations where the change of dipole moment is parallel to the A axis should have the P&R structure characteristic of parallel bands in symmetric top molecules. For the P - R separation AY(P - R) of such bands the formulae of GERHARDand DENNISON[19] give a value of about 10 cm-l at ambient temperature.
I(C,)
II
Fig. 1. The two main conformers of HFP.
In the vapour i.r. spectrum of HFP, there are three bands, at 1117, 689 and 350 cm-i, with a clear P&R type struoture, Av(P - R) being about 9 cm-l in each case. The band at about 1117 cm-l is missing in the spectrum of HFP-CD, and there is an A-type band at 1028 cm-l (A@’ - R) about 9 cm-l). Bands with apoorlyresolved P&R structure are found at 1379 and 894 cm-l in the vapour spectrum of HFP. There are two bands in the vapour spectrum of HFP at about 535 end 550 cm-l that partly overlap. It seems probable that one or both of them are type-B bands, Av(Q-Q) being4-5 cm- l. HFP-CD has a B-type band with peaks at 643 and 648 cm-l, Only one C-type band was found, at 738 cm-l, in the vapour spectrum of HFP. The asymmetry parameters of UEDA and SHIMANOUCHI [20] for HFP are 2 = l-75, y = -0-338. We can deduce from the figures published by these authors that a 1: 1 B/C hybrid band of HFP would be triangular and that a C-band would be similar to that found st 738 cm-i (Fig. 2). There are indeed triangular bands at 1205, 833 and 514 cm-l, possibly also at 3626 end 1244 cm-l, in the spectrum of gaseous HFP (Figs. 2 and 3). Some bands, such as the OH and CH stretching bands, are doublets, obviously because of conformational heterogeneity and intramolecular interactions [2, 3, 211. [18] R. M. BADQER and L. R. ZUMWALT, J. Chm. Phya. 6, 711 (1938). [I91 5. L. GERHARD and D. M. DENNISON, Phya. Rev. 43,197 (1933); W. A. SETH PAUL and G. DIJKSTRA, S~ecbrochint. Acta 23A, 2861 (1967). [ZO] T. UEDA and T. SHIMANOUCHI, J. Mol. Spectry 28, 350 (1968). [21] K. F. PURCELL, J. A. STIKELEATEER and S. D. BRUNK, J. Mol. Spectry 32, 202 (1969).
1124
JUEANI MURTO, AWCCI KIVINEN, REA VIITALA and Jowo
3700
I
3600
I
I
900 cm-’
HYGMXICI
I
I
so0 I
700
Fig. 2. Band contours in i.r. spectra of HFP vapour. The 6 cm cell was cooled with dry ice in a polythene bag. A, pressure 26 mmHg; B, pressure IS mmHg (at room temperature).
3700 36003OoO2900
1400
1200
1000
so0
600
600
400
300
cm-l Fig. 3. 1.r. spectrum of gaseous HFP. A, 10 om cell, pressure 4 mmHg; cell, pressure 6 mmHg.
B, 1 m
Also splitting of the skeletal and CF stretching bands into doublets was observed in the spectra of HFP in nitrogen and carbon monoxide matrices [3]. It is obvious that the presence of bands due to two conformers complicates the band envelopes. Thus, for example, the band at 460 cm-l consists of two weakly separated maxima 3-4 cm-l apart, and the envelope might be that of two narrow triangular bands that have shifted slightly apart. The same may apply also to the band at 327 cm-l. About ten of the bands (for each alcohol studied) were completely or almost completely depolarized, which indicates that the molecules have symmetry. The lowest depolarization ratios (ca. 0.04) were found for symmetric skeletal stretchings. Vapour spectra of HFP were recorded also at temperatures up to 200°, but no marked changes were noted (except broadening of the bands and a shift of the band at 3666 cm-l that is discussed below).
Infraredand Raman spectra of hexafluoro-2-propanol
1125
The ~e~~~ dwve 1500 OX+ OH (OD) stretching. The YOH doublet is at 3666 and 3626 cm-l in the spectrum of gaseous HPP (Fig. 2). As mentioned above, the doublet character of the OH stretching band is due to conformational heterogeneity and intramolecular interactions. In the matrix isolation study [3] it was found that the lower-frequency band is really a doublet due to two conformers in nitrogen and carbon monoxide matrices and that there are thus three different conformers. No band due to the C, conformer was seen in the spectrum of HFP in an argon matrix [3].
5i--- 2900
I
1400
,
I,
I,
1200
IO00
I,
800
I
600
I,
I
400
200
cm+
Fig. 4. Barnan epeotrum of liquid EFP excluding the OH stretching region.
If the temperature of the HFP vapour is varied, the sharp peak at 3626 cm-l remains fixed but the broader, smaller peak at 3666 cm-l shifts to higher frequencies with decreasing temperature at a rate of -0*026 cm-l K-l; this shift has been noted also by MILLEN [22]. The envelope of the vOH (or YOD) doublet was very similar in the vapour spectra of all four isotopically different alcohols. The peaks are at 2704 and 2675 cm-l in the spectrum of HFP-OD vapour, the ratio YOH/YOD being thus 1.35. Doublets (due to terminal OH (Of)) groups or to monomers) are seen as shoulders on the broad polymer bands in the i.r. and Raman spectra of the neat liquids Figs. 5(b) and 5(c)]. The bands are doublets also in the spectra of carbon tetrachloride solutions. The maxima are at 3615 and 3578 cm-l in the case of HFP [Z, 41; the relative intensities of the two peaks are the reverse of those in the vapour spectrum. The enthalpy difference between the two conformers in carbon ~trac~oride is 0.6 kJ mol-r[2], whereas it is 4.6 kJ mol-l in the vapour [22]. Thus, carbon tetrachloride seems to stabilize the higher-energy conformer, similarly as do the nitrogen and carbon monoxide matrices. The doublet splitting is still more marked in spectra of solutions of HFP in hexafluorobenzene; no splitting is seen in spectra of benzene solutions [4], The two OH stretching peaks of WFP differ with regard to anharmo~city in carbon tetrachloride; the anharmonicity constant is 82 cm-i for the C, and 62 cm-i for the C, conformer [4]. It is about 50 cm-l for both conformers in the vapour. 1221 13. J. MILLEN,Private coxnmunication.
1126
JUHANIMUR~O, ANYCI KIVINEN, REA VIITALA and JOTJKO HY~WUI
I
4000 cm-1 Fig. 5(a). The OH stretching region in the ix. spectrum of HFP vapour in a 1 m cell, pressure 95 GnHg.
1
I----
t
s 6
z E z
z 400
I
3500
I
I
3000
3500
cm-1 Fig. 6(b). The OH stretching region in the i.r. spectrum of liquid HFP, KBr windows, cell thickness O-02mm.
The two main conformers are obviously those shown in Fig. 1. The higherfrequency band has been assigned to the “free” conformer (C,) [2, 31. It may be mentioned that the i.r. spectrum of gaseous l,l,l-trifluoro-2-propanol shows only one YOH peak (at 3651 cm-r) [23], and so does also the spectrum of S-phenyl-hexafluoro-2-propanol (the peak is at 3628 cm-l). [23] J. MTJRTO, A. KMNEN and K. EDELMAN,unpublishedresults.
Infrared and Raman spectra of hexafluoro-2-propanol
3600
3400
3200
3000
2600
2600
1127
2400
cm-1 Fig. 5(c). The OH and OD stretching regions in the Raman spectra of liquid HFP (A) and liquid HFP-OD (B).
cm-l Fig. 5(d). The OH stretching region in the i.r. spectra of solid HFP (C) and solid HFP-CD (D). Cell thickness 0.025 mm, temperature -190“.
There occur sum and difference bands of the OH stretching vibration and several low-frequency fundamentals in the vapour spectra Fig. 5(a)], and these relate to the lower-frequency OH stretching peak only. The most intense combination bands of this type in the spectrum of HFP are at 3626 f 329 cm-l (due to G-C-C bending), 3626 + 287 cm-l (due to OH torsion) and 3626 f 248 cm-l (due to CF, rocking). The only intense combinations in the vapour spectrum of PFTB were YOH -& TOH [12], which were relatively more intense than the corresponding bands
1128
JVEAXIMUXWO, AX!~TIKIVINEN, REA VIITAL~Land JOWEO EY~MXEI
in the spectrum of HFP. If water is present in HFP vapour, a broad HFP-H,O complex is seen at 3450-3500 cm-l [24]. A marked ~sociation band of the OH stretch~g is seen in the i.r. and Raman spectra of the liquids [Figs. 5(b) and 5(c)], although the tendency of HFP to associate is considerably weaker than that of 2-propanol [l, 31. The association band is broad and featureless, also in the Raman spectrum obtained after turning the analyzer 90’ (marked 1. in the figures). The vOH ~ociation bands of nonhalogena~d alcohols show two maxima in the 1 spectra [25]; the minimum between them obviously corresponds to some symmetric associate structure. Only a broad polymer band is seen in the spectra of the solid alcohols in the OH stretching region [Fig. 5(d)]. Sometimes, however, the band has a shoulder and there are small differences also in the CF stretching region. The crystal form may thus have been different when the different spectra were recorded (cf. [.26]). There were three “fingers,” at 2890, 2760 and 2640 cm-r, in the spectrum of solid HFP [Fig. 5(d)] that were weaker in the spectrum of liquid HFP and almost absent from the spectrum of the vapour. Similar bands are seen in the spectrum of solid phenol [27]. The most probable explanation is that they are due to overtones and combinations of the two OH bending association bands and possibly also of the CH bending band at 1380 om- l; these “borrow” intensity from the vOH association band. The association band occurs at lower frequencies in the solid state than in the liquid state, and thus the fingers are most intense in the spectra of the solids. Only two fingers of marked intensity are seen in the spectrum of solid HFP-CD [Fig. 5(d)] (note that there are no CH vibrations in this compound). HFP-dB has only one finger (at 2165 cm-l), and so obviously has also HFP-OD (at 2035 cm-l). CH (CD) stretching. The rCH band of HFP is also a doublet in the spectrum of the vapour (peaks at 2984 and 2943 cm-l) and of the carbon tetrac~o~de solution [a], but not in the spectrum of the neat liquid or the solid. Also in this case the intensity ratio is reversed when going from the vapour to the Ccl, solution. Both peaks are round and featureless in the vapour spectrum. The peak at 2984 cm-l in the vapour spectrum is more intense than that at 2943 cm-l, and thus we consider the former peak to correspond to the C, conformer. It is difficult to identify the CD stretching band in the i.r. spectra of CD deuterated fluoroalcohols as it is inherently weaker than the CH stretching band and is situated in the region of the overtones of the intense CF stretching bands. The doublet is most clearly seen in the spectrum of HFP-CD in carbon tetrachloride (peaks at 2 188 and 2165 cm-1 [a]). The CD stretching band is intense in the Raman spectra and is at about 2200 cm-l. The CH stretching band is a doublet also in the spectra of 2-propanol. This has been attributed 1283to ~~ra~tion between the C--H bond and the lone electron pair of oxygen. [24] M. A. HUSSEIN, D. J. MILLEN and G. W. M&ES, Chm. Commun. 172 (1970). [26] J. MURTO and A. KXVLNEN,unpublislmd results. [.26] J. MURTO,A. KIVIHENand K. HAXSTE, de& Chmz. Smnd. 24,3057 (1970). [27] J. C. EVANS, S~e&rochim.dcta IS, 1382 (1960). [28] P. J. KRTJE~ER,J. JAN and H. WIESER,J. Mol. Struct. 5, 375 (1970).
Infraredand Ramsn spectraof hexafluoro-2-propenol
1129
The region 1500-1100 (1600-900) cm-l In this region we expect to find six CF stretchings (3~’ + 3a”), an OH in-plane bending and two CH bendings (a’ + a”). The CF stretching bands are very intense and mask other, weaker bands, and also, because of coupling effects, the positions and intensities of bands may be different from those for other alcohols. Thus the band assignments based on group frequencies can be only very approximate at best (cf. [29, 30-j). In the assignment we rely in many respects on the matrix isolation study [3]. OH (OD) in-plane bending. The 60H vibration of alkanols has been discussed in several papers [31--331. Because of heavy coupling of this vibration with other vibrations, there are usually several bands in the spectrum that can be ascribed to OH bending [31, 321. The bands at 1311 (HFP), 1004 (HFP-OD), 1328 (HFP-CD) and 1067 cm-l (HFP-d,) in the spectra of argon matrices [3] were ascribed to OH (OD) bending; these were all relatively strong bands. The corresponding bands in the vapour spectra are at 1308, 1000, 1318 and 1069 cm-l, respectively. The position of about 1300 cm-l seems well founded for the OH bending band because the band is at 1250 cm-l in the spectrum of gaseous 2-propanol [El, and it shifts to higher frequencies almost linearly as the number of fluorine atoms increases in fluorinated tertiary butyl alcohols [12,34] (the frequency increases from 1330 cm-l in the spectrum of t-butyl alcohol to 1381 cm-l in the spectrum of PFTB). Although the intensities of the OH bending bands of hexafluoro-2-propanols mentioned above undergo no marked changes on going from vapour to liquid to solid, there is considerable evidence in favour of the assignments (Tables l-4), viz., the matrix isolation spectra [3], analogy with fluorinated butanols [12, 341 and the positions of the overtones (fingers). The band at 937 cm-l in the spectrum of HFPCD disappears on going from the vapour to the solid, but this frequency is too low for an OH bending band (the band may, however, have some 80H or 70H character). The reason for the insensitivity of the OH bending to change of phase and for its high intensity must be its coupling with other vibrations. There is a broad association band at 1425 cm-l in the i.r. and Raman spectra of liquid HFP. There is a polarized band at 1310 cm-l in the Raman spectrum of liquid HFP; in the spectra of aqueous mixtures [4], this band is broader and at about 1340 cm-l (the band at 1290 cm-l has not moved) and the band at 1425 cm-l has shifted to 1455 cm-l. Both of these bands are absent from spectra of liquid HFP-OD and are obviously association bands. The band at 1430 cm-l in the i.r. spectrum of solid HFP-CD is with certainty and the band at 1348 cm-l probably an association band. CH (CD) bendinga. Although the in-plane (a’) CH bending usually occurs at a higher frequency than the out-of-plane (a”) bending [15, 351, this order is reversed [29] E.
C. TUAZON, W. G. FATELEY and F. F. BENTLEY, AppZ. &e&y a, 374 (1971). H. F. SEURVELL and J. T. BULUEB, J. FZuor. Ohem. 1, 391 (1971/72). A. V. STUART and G. B. B. M. SW, J. C?mn. Phye. 24, 669 (1966). S. Km&f& C. Y. LIAXU and G. B. B. M. SUTHE~AND, J. Chem. Phys. 25, 778 (1956). P. TARTE and R. DEPONTH&RE, J. Chmn. Phya. a6, 902 (1957); BuU. Soo. C&a. Be&m 66, 626 (1957). [34] J. KORPPI-TOMMOLA, unpublished results. [35] C. V. BERNEY, Spectrochim.Acta 25A, 793 (1969).
[30] [31] [32] [33]
1130
JUEAN-I MURTO,
ANTTI
KIVINEN,
VIITALA and Jowo
REA
HYGMXEI
Table 1. The observed i.r. and Raman frequencies (cm-l) for (CF,),CHOH the region 2600-1500 cm-l) vapour i.r.*t 7240 7160 3964 3912 3873 3666 3630 3626
Liquid RWWIl$
Liquid i.r.
“VW vvw vvw VW VW
2670 vvw 2603 ww 1415 w 1379, A? 1360 sh 1308 v8 1273 s
2966 VW > 2876 vvw 2760 vvw
P
2968 (~26)
2616 vvw 1427 w
1425 (2)
1379 1360 1310 1289
1380 1360 1310 1290
8 sh sh, vvw “8
3260 br, s**
P
(4) (
P
0.2
P DP 0.8 DP P P 0.3
1258 s
1260
DP
1263 B 1 1244 WB 1227 sh
1233 VB 1220 V8
1236 12201
DP
1205 ““B B/C
1188 vvs
1194 (4)
DP 0.8
(-1135) 1122 sh 1117~~s A 1113 sh 1 1070 sh 1016 sh 983 vvw 894 m A? 833 m B/C 738m 0 693 689 s A 684 1 610 vvw 670 664 Br 548 1 * 637 632 I w B1 620 sh 614~ B/C 460 466
Assignments 11 2 X 3666 2 x 3626 3626 + 327 3626 + 287 3626 + ~248 a’vOH, 0, conformer
vvw ““TV VW vvw “VW w sh7 m 3630 sh 3592 sh 3430 br, m
3377 3336 3296 2984 2943
Solid i.r. (-75’)
(excluding
1128 (7) 1108 VVB
1108 (7)
P <
0.3
NDP 0.7
2980 VW 2890 2760 2665 2640 1452 1429 1378
w w VW VW m VW VB
1338 w 1292 “8 1260 sh 1254 shtt 1246 vs 1222 “8 1200 B 1186 WB 1179 “VB 1161 sh 1118 vvs 1106 vvs
a’vOH, C, conformer > terminal vOH, 0, conf. terminal vOH, C, conf. yOH, associated 3626 - ~248 3626 - 287 3626 - 327 a’vCH, C, conformer a’vCH, 0, conformer 2 x 1427 2 x 1379 1268 + 1379 2 x 1310 a’ 60H, assooiated 2 x 738 a” 6CH 2 x 688 a’60H. associated a’60H. o’vCF, a’ 8CH a” vCF, a’vCF, > 2 x 610 abvCF, > 327 + 333
a’vCFs
a”vCF,
7418
327 + 738 2 x 614 460 + 614 a” vcc a’vC0, msocktted a’ vco a’vCC
686 “8
a” 8CF,
636 br, mtt 610 m
TOH, associated? a’ 6CF, 1308 - 738
DP
548 VW
a” 6CF,
536 (6)
DP 0.7
532 w
617 w
519 (11)
P 0.5
460 w
463 (19)
P 0.2
a"dCF, a'GCF,;1205 a'GCF, a'6CO
895 m 841 m
896 (2) 838 (68)
737 m
739 (100)
686 B
687 (4)
610~~
613 (16)
652 VW
561 (1)
636 w
DP 0.8 P 0.04 P 0.04 DP 0.8
P 0.5
894 v8 847 8
613 TV
1308 -
894
-
688
1131
lkfrtwed and FCaman spectra of hexaftuoro-2-propanol Table 1. (cont.) V8pOW i.r.*t
396 “VW 382 vvw 373 vvw 365 360 w A 346 1 329 326 >m 287 w 232 VW
Liquid i.r.
Solid i.r. ( - 76’)
Liquid Rsman$
Assiientg~ 1135 894 833 -
360 vvw
360 (IS)
327 vw
328 (63)
296 288 262 237
297 (8)
vw sh vvw? vw
244 br(2) 167 (3) 100-120 br (< 1)
DP 0.8
a= &Jo
P 0.2
O’GCC
DP 0.8
P 0.6 P o-2 DP?
738 514 468
ax pUFs d TOH a’ PDF, 6’ pCF, a’ PWS Y (H-bond)7
* The letters A, B and 0 refer to the band type. ah = shoulder. t Overtone btmds were found Jso at 248112 x 1244), 2370(2 x 1206), 2240(2 X 1135), 2208(2 X 1117), 1790(2 x 894) snd ISSO(2 x 833) em-x. $ The spproximete Raman intensities are given in parentheses. P = polarized, DP = depolarized band; the velues after these are the depolarization ratios. 4 v = stretching, 6 = bending, p = rooking, 7 = torsion. 11 The assignment of combination and overtone bands is based on vapour-state frequencies whenever possible. fi Is seen if the oell is cooled below 0”. l * 3230 em-l at - 190°. tt seen only at -WY. $$ BBOcm-* et --190°.
in the case of HFP [3]. The strong band at 1379 cm-l in the v&pour spectrum of HFP displttys some P&R structure and obviously relates to the ~~rnet~c bending. This bsnd disappears on CD deuteration (it is missing also from the spectrum of 2-phenyl-hexafluoro-2-propanol [25]) and is depolarized in the Raman spectrum of liquid HFP. Hexachloro-2-propanol also has a band at about 1380 cm-l, but this is a doublet in cccrbon ~tr&c~o~de solution [25]; the oo~espon~g band of HFP is & singlet. In no spectrum was the sntisymmetric CD bending found, not even in the matrix spectra [3]. The band at 1272 cm-l in the spectrum of HFP in the argon matrix wits assigned to s~rnet~c CH ben~g. We can deduce from the booty and pol&ri~~tiond&a of the Raman spectra that the symmetric band is at 953 cm-l in the spectrum of liquid HFP-CD and at 897 cm-l in the spectrum of liquid HFP-d,. The value of the OD bending band is 69 cm -1 higher for the latter alcohol than for HFP-OD, and we can deduce that the energy levels of symmetric CD bending and OD bending repel each other in HFP-d,. CF &etchings. These bsnds occur usualIy between 1100 and 1400 cm-l and are the strongest ones in the i.r. spectra, but relatively weak in the Raman spectra. The six CF stretching bands of HFP are somewhat similar to those of HFP-OD, but differ in location from those of the CD compounds (Figs, 3 and 6). The frequencies of the vibrations of the CD compounds are similar to those of 2,2-diaminohexafluoropropane [8], a compound with no CH or OH groups.
1132
Jo-
MIJRTO, ANTTI
KIVINEN,
VIITALA and Jouxo
REA
HY~I&&I
Table 2. The most important ix. and Reman bands of (CF&CHOD vepour i.r.
2987
VW
2943VW
Liquid Reman
Liquid i.r.
>
2960VW
2971(N40)
2736 sh
2730 ah
Solid i.r. (- 75’)
P 0.15
2980 w
2704 w 2675 m
1383 1380 1303 1286 1273 1242
sh BI “S vs B/O sh vvs
1216 W8 1142~1 1117 ““8 1000 935 901 896 892 870 840
m sh ah m sh I sh sh
805 w B/U 726 w 692 688 m A 683 I 601 vvw 553 548 > vw 536 531 Iw 513 w B/C 455 451 >w
332 327 Im 265 VW 210 br. w
2680 sh 2651 sh 2540 br, m
2680 eh 2652 sh 2550 br (~10)
1390 sh
1390 sh
P 0.1 P 0.1 P 0.3
DP 0.8
1380 8
1380 (7)
1289 VB
1290 (10)
1260 sh 1236 ah
1264 1237
1205 ““B
1210 (6)
P 0.6
1109 VW
1128 (9) 1109 (9)
P < 0.3 DP 0.8
1004 m
1005 (3)
DP 0.6
894 m
897 (3)
DP 0.8
P 0.5 DP DP?
2430 2400 2035 1396
br. et ah VW “8
Assignment* o’vCH, 0, conformer o/&H, 0, aonformer o’vOD, 0, conformer a’vOD, 0, conformer terminal YOD, C, oonf. terminal vOD, 0, oonf. a’vOD, associated o’vOD, associated 2 x 1025 2 x 726
1378 “B
o” 6CH
1290 s 1284 8 1255 m 1235 sh 1215 V8 1200 ““B 1180s 1123 s 1107 ““B 1025 *
a’ vCFI a’ 6CH a” vCF, cs”vCF* a’ 6OD. aaaocietedl a’ vCFt
893 8
2 x 610 o’vCFI a” vCFI a’ 6OD, aclsocisti a’ 6OD 330 + 600 a” vcc
813 w
813 (63)
P 0.04
845 vvw 826 m
733 m
733 (72)
P 0.05
737 8
330 + 534 330 + 513 a’vC0, esaooiated a’vC0 a’vCC
687 s
688 (4)
684 ws
o” gCF$
610 VW
611 (22)
610 m
a’ SCF,
550
550 (1)
DP
550 VW
o” 6CF,
DP 0.8 P 0.6
535 w
535 (8)
DP 0.8
535 w
a’ dCF,
516 w
515 (16)
P 0.6
515 w
o’ BCF,
455 w
460 (27)
P 0.4
352 w
348 (22)
DP 0.8
326 m
329 (100)
299 sh
298 (11) 239 (3) 167 (3) 90-110 br (1)
P 0.4 DP 0.8 P 0.4 P 0.15 DPP
0’6CO
a” 6CO O’GCC
or ,&F8
,” ,oCFs (i’ pCF, o” TOD a’ pCF, v (D-bond)?
* The Basignment of oombination Rnd overtone benda is based on vapour-state frequencies whenever possible. t Not soon in all spectra.
Infrared and Reman spectra of hexafluoro-2-propanol
1133
Table 3. The most important i.r. and Raman bands of (CF.J,CDOH vapour i.r.
Liquid RlIRlan
Liquid i.r.
Solid i.r. (- 76’)
3668 w 3628 m
1318 vs
3636 sh 3660 sh 3480 br. m
3640 3600 3460 br
P < 0.2 P < 0.2 P < 0.2
2202 (-33) 1390 br (< 1)
P 0.2
1390 w 1314 s
1316 (6)
P 6.4
1223 vv8 1168m 1132 vs
1032 1028 8 A 1023 937 w 880 eh 814 m B/C 735m 0 673 669 s A 664 648 w B 643 1 631 VW 616 sh 612 w 467 454 >w 356 360 w A 346 1 830’ 325 Im
1019 “B
1266 1231 1226 1170 1145 1132 1072
sh sh? (3) (ml) (1) sh (< 1)
1020 (2)
DP? P 0.6 DP P P? DP 0.76
3290 br, st 3230 sht 2844 VW 2716 VW 2185 VW 1430 m$ 1348 “VW 1311 vs 1306 sh 1256 m 1228 VVB 1210 vs 1168 w 1161 sh 1142 ~811 1068 WTV
a’ vOH, C, conformer terminal YOH, C, oonf. terminal YOH, C, aonf. a’ vOH, sssooiated a’ vOH. associated 2 x 1430 2 x 1348 a’ YCD a’ 60H, associated a’60H, associated? a’SOH, a”vCF, 2 x 669
a’VCFs axvCF,
a’vCF, a” vCF* a’vCF,; 328 + 814 1 (FR?j)
960 VW 940 sh 882 VW 816 In 734m
963 (22) 940 sh
P 0.2
1020 va 1010 sh 966 ww
817 (100) 736 (60)
P 0.1 P 0.1
897 VW 820 8 739 m
a’ vcc > a’ 6CD 289 + 669 2 x 456 a’vC0 O’VCC
667 B
660 (6)
DP 0.8
666 B
a” 6CF,
608 VW
611 (13)
P 0.6
604 w
a/&F,
646 VW
646 ah
DP
a” 6CF,
636 vw
638 (6)
DP
614w
516 (9)
P 0.6
ax SCF, a’9CF,? a’SCF*
468 w
463 (18)
P 0.3
a’&0
362 (13)
DP 0.8
330 (48)
P 0.3
296 (6)
DP 0.8
240 (2) 170 (3)
P 0.6 P 0.2
289 w
* t band 2
l
a’ YOH. C, oonformer
1238 WB Al 1177m 1162 “I3
Assignment
a” SC0 a’GCC a’ a’ a’ a’
pCF, TOH pCF, pCF,
The assignment of combination and overtone bands is baaed on vspour-state. frequencies whenever possible. The vOH association band at -100’ was either a doublet with peaka at 3230 and 3166 cm-1 or e single et 3230 cm-‘. 1440 om-l et - 100”. FR denotea Fermi resorunce. t) Thin bend is wan as e shoulder on the band at 1161 cm- if the lower-frequency vOH aesooiation band is miseing.
a’ VOD, 0, a’ YOD. c,
2680 vw 2MO Yw 26150br. m
2650 2560 br (~10)
P P P
2180 vvw
2140 f-35)
P 0.3
1323 (9)
P 0.4
1345 sh
1340 sh
1322 “8
1320 vs
1072 (7)
P > O”3
1325 sh 1318 YS 1283 s 1233 vvs f212 vs 1200 sh 1167 sh 11518 1087 s
1520 (2)
P
1013 vs
1235 br (4)
1240 vvs
DP
1224 vvs 1177 w 1156 B X089 m 1032 1028 s A
1024 I 900m 870 sh, w 799 m 721 m 675 670 a A 665 1 600 vvw 049 841 > W 631 VW 813 w 452 448 I=
1169 sh 1149 va 1068 m 1020 s
>
2460br, 8 2400sht 21652 2165vw I3508 1341ah
1170 br (1)
DP
895 br, w
897 (6)
PO.4
902 VW
802 w 728m
805 (100) 730 (46)
P 0.54 P 0.06
813 m 733 m
665 s
686 fe)
606 VW
613 (17)
544 VW
545 sh
DP
834 w 513w
538 (4) 616 (10)
DP P 0=4
453 w
460 {24f 420 (3) 361 (19) 330 (90) 300 (7) 240 (21 170 f3) 9~12Osb
DP 0.8 PO+4
conformer conform%r
terminal POD, 0, conf. terminal vQD, 0, conf. a’yOD,
associated
Q’YCD 2 x 1087 I >
a” YCF, a’vCFa
a” YGF$ a’&I$ 1 a’&Fa a” vCF, u’60D
a’ YCD 2 x 450 a’vC0 a’vCC
663 s 607 vvw
P 0‘2 P DP P 0.3 DP P
a” 6CO O’GCC a” ,&F, a’ pCF, !a’ pCF, v [D-bond)?
* The assignment of oombinations and overton@@ IS based on vapour-state frequencies whenever possible. t Not seen in all a3pectra.
There are two bands slightly above Xl00 cm-I in the Raman spectra of liquid HFI? and HIV-OD that axe seen also in the ix. speotra of the solids and in the matrix spectra, but not in the ix. spectra af the liquids and of gaseous HFP, These are considered to be two fundamentals. One of these bands is at 1117cm-l in the speotrum of gaseous HFP and obviously masks the other, muah weaker c&‘-type band at about 1135 cm-l. Two sharp peaks are seen at 1283and 1273 OM-1in the vapour spectrum of HPP (Fig, 3). We consider them to be twa different fundamental bands, but they may also be due to Fermi resonance (cf. [36”J)or conformational splitting.
Infrared and Raman spectra of hexafluoro-2-propanol
The region 1100-700
1136
cm-l
In this region there are the three skeletal stretchings (2a’ + a”) that are easily identified. The band at 738 cm-l in the i.r. spectrum of gaseous HFP is of C-type; the band is highly polarized in the Raman spectrum of the liquid. It is the strongest band in the Raman spectrum of HFP and is clearly due to the symmetric C-C-C
L
I
I
1400
I !
I
1000
cm’-’ Fig. 6. The CF stret&ing region in the i.r. spectrum of gaseous HFP-CD, 10 cm cell, pressure 8 mmHg.
stretching. This vibration produces strong, highly polarized bands also in the Raman spectra of hexafluoroacetone, (CF,),C=X=Y type compounds and TCHFB. It is located at 726 cm-l in the spectrum of gaseous HFP-OD. The band at 838 cm-l in the Raman spectrum of HFP is strong and polarized and must represent mainly the CO stretching. In the vapour spectrum it occurs at 833 cm-l and shifts on OD deuteration to 805 cm-l and on CD deuteration to 814 cm-l (vapour values). In the spectrum of HFP-dE,it is found at 799 cm-l. The association band of CO stretching is on the high-frequency side of the monomer band in the spectra of all isotopic HFP’s (cf. also [a]). The band at 894 cm-l in the vapour spectrum of HFP is weak and depolarized in the Reman spectrum and is due to asymmetric G-C-C stretching. In the spectra of the CD deuterated compounds it is located at 1028 cm-l, presumably as a consequence of interaction with the CD out-of-plane bending which is not observed [3], and displays very clearly a P&R structure.
1136
JTJEUNIMURTO, ANITI KIVINEN, REA VIITALA and Jowo
HYZ~MXKI
The region ‘700-300 cm-l
There should be six CF, bendings (3a’ + 3a”) and three skeletal bendings (2a’ + a”) between 700 and 300 cm-l. It is also possible that one of the CF, rockings is above 300 cm-l. The association band of OH torsion should also be in this region. CF bendings. The 6CF, bands are usually between 450 and 750 cm-l. The band of gaseous HFP centred at 688 cm-l shows the P&R structure (Fig. 2); the band is depolarized in the Raman spectrum of the liquid. Slightly above 600 cm-l there is a band in the spectra of all isotopic HFP’s that is very weak in the i.r. spectra and polarized in the Raman spectra. We assign these two vibrations to asymmetric and symmetric combinations, respectively, of the “umbrella” vibrations, as these usually occur at higher frequencies than the other CF bendings [6]. The band of the asymmetric vibration is at about 670 cm-l in the spectra of the CD deuterated compounds. The other CF bending bands occur obviously between 500 and 550 cm-r. The most intense of these is the band at about 515 cm-l (in both the i.r. and Raman spectra). It is possible that the symmetric CO bending vibration contributes to this band. Skeletal bendings. The band at about 330 cm-l is obviously due to the C-C-C bending. It is very strong in the Raman spectra (it is the strongest band in the Reman spectrum of liquid HFP-OD; cf. also [4]) and its frequency seems to vary only relatively little with structure in spectra of compounds of type CF,CCF,, even when the central carbon is spa hybridized [Q]. The other two skeletal bendings can be roughly described as CO in-plane and out-of-plane bendings. There is a depolarized A-band at 350 cm-l in the spectra of the IIFP’s which we ascribe to the latter vibration. The only remaining band still unaccounted for in the 300-700 cm-l region is the band at about 460 cm-l; in the Raman spectra it is relatively intense and polarized. We ascribe this to the CO in-plane bending. The association band at the OH torsion. This band should be characteristically broad and intense. It is seen at about 640 cm-l in the i.r. spectrum of liquid 2propanol, the half-width being about 200 cm-l. The association band is more indeterminate in the i.r. spectrum of liquid l,l,l-trifluoro-2-propanol and is situated between 600 and 700 cm-l [23]. No corresponding band was found in the spectrum of liquid HFP. A much weaker and narrower (half-width 30-40 cm-l) band was found in the i.r. spectrum of solid HFP at 635 cm-l at a temperature of -75’; at -190’ it was at 660 cm-l. It is possible that this band is the association band of OH torsion. The region below 300 cm-l
There should be in this region the torsion band of nonbonded OH groups, four CF, rocking bands (2a’ + 2a”) and two CF, torsion bands (a’ + a”). The CF, torsion bands were found at 48 and 66 cm-l in the i.r. spectrum of hexa5uoroacetone [6]; a 10-m path length cell is required when studying them. Also the frequencies of the hydrogen bonds are below 300 cm-l. Free OH torsion. The TOH band is obviously at 287 cm-l in the vapour spectrum of HFP and at 289 cm-l in the spectrum of HFP-CD. A broad band centered at
1137
Infrared and Raman spectra of hexafluoro-2-propanol
300
200
100
cm-’ Fig. 7. Raman spectrum of the low-frequency region of liquid HFP-OD. speotrum of HFP is very similar in this region.
The
210 cm-l was seen in the i.r. spectrum of gaseous HFP-OD; this is obviously the OD torsion band. CF, rockings. There are three bands in the Reman spectra (at 167, 239 and 298 cm-l in the spectrum of HFP) that very probably are caused by the rocking vibrations pCF, (see also Fig. 4). Those at 167 and 239 cm-l are polarized and are thus due to symmetric vibrations. The fourth band was not found in the vapour spectrum of HFP, but in the spectrum of HFP-OD there was a band at 265 cm-l that might be the fourth rocking band. This is not seen in the vapour spectrum of HFP because of the much stronger, broad OH torsion band. It may be mentioned that bands at 160, 233, 265 and 275 cm-l have been ascribed to CF, rocking vibrations in case of hexafluoroacetone [6]. Hydrogen bond stretchings. These vibrations occur usually between 100 and 200 cm-l in the spectra of alkanols [37]. In the Raman spectra of HFP and its deuterated derivatives, there is indication of a band at about 100-120 cm-l (Fig. 7), which we ascribe (very tentatively) to hydrogen bond stretching. Aclcr+owledge~~ts-For preliminary measurements we are grat&zl to Mr. MAP NXsuX, Ph. Lit. and Mr. JOOKOKORPPI-TOMMOLA, Ph. Lit. We thank also Dr. A. J. BARNES(University Collegeof Swansea,Wales) for helpful discussions,Dr. W. A. THOU (Swansea)for recording the ?F NMR spectra, and Dr. J. KANKAIG (University of Turku, Finllmd) for checking the frequenciesof the low-frequency vapour bands with a Perkin-Elmer 180 spectrometer. We are also grateful to the Finnish State Council for Sciences for research grants. [37] R. F. LAXE and H. W. THOMPSON, Proo. Roy. Sot. 29lA, 469 (1966).