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Use of 1H NMR spectroscopy to study petroleum alkylcarbazoles. Monomethylcarbazoles
Use of IH N M R spectroscopy to study petroleum alkylcarbazolea
~)27
80. Informatsionnyi listok No. 132-83. Repellent dlya zashchity zlzivotnykh ot gnusa ( I n f o r m . tion Leaflet No. 132-83. Repellent for Protecting Animals Against Blood-Sucking Flies), TsNTI, Tyumen, 1983 81. G. Ye. RADTSEVA, N. N. RYAKHOVSKAYA, A. IOI. S H A R I P O V and L. M. ZAGRYATSKAYA) "Fez. dokl. XIV nauchn, sessii po khimii i teidanologii organicheskikh soyedinenii sery i sernistykh neftei (Abstracts of Papers of Fourteenth Scientific Session on Chemistry and Technology of Organic Sulphur Compounds and Sulphur Crude Oils), 103 pp., Zinatne, Riga, 1976
0031-6458188 $10.00+.00 © 1990 Pergamon Prets pie
Petrol. Chem U.S.S.R. Vol. 28, No. 4, pp. 227-234. 1988 Printed in Poland
U S E O F 1H N M R S P E C T R O S C O P Y TO STUDY PETROLEUM ALKYLCARBAZOLES. MONOMETHYLCARBAZOLES* M. B. SMIRNOV, YE. B. FROLOV, N. A. VANYUKOVAand P. I. SANIN A. V. Topchiyev Institute of Petrochemical Synthesis, U.S.SR. Academy of Sciences
(Received 22 April 1988)
TR'E composition and structure of compounds of higher distillates and residual fractions of crude oils ~emain little studied. As is known, neutral nitrogen components (mainly 9-H-alkyl-and benzocarbazoles) predominate in the heavy part of crude oil [I] 5
8
4
tt 9
1
In the first investigations, when studying concentrates high in neutral nitrogen compounds, high-resolution mass spectrometry was used to obtain the MW distributions of alkyl- and benzocarbazoles (see, for example, [2, 3]). The structure of the substituents and their position in the rings have still not been established. A detailed study of petroleum carbazoles has now become possible only by developing selective methods for isolating this type of compound from crude oils [4, 5]. Most attention has been paid to procedures for analysing the individual composition of the fraction. In a number of crude oils, about 20 individual carbazoles (mainly mono- and dimethyl-substituted carbazoles) have been identified [6]. At the same time, formulation of the general problem of total analysis of the individual * Neftekhimiya 28, No. 6, 739-745, 1988
22.8
M.B.
S~tmNov er al.
composition of petroleum carbazoles is virtually impossible in that theoretically there are 210 isomers of C4-alkylcarbazoles alone. Group-structural analysis (GSA) methods must be developed. The main aim of such studies should be to Obtain information on the structure of the substituents and their distribution in the heterocyclic system of the carbazole for fractions as a whole. In practice, such data can be obtained only by means of NMR spectroscopy. However, no procedures of this kind have been developed for any type of heteroatomic compound. N M R spectra of 9-H-alkyl- and bznzocarbazoles have hardly been described [7-9]. Thus the potential of NMR. for solving this problem cannot even be assessed on the basis of published data.
#
7
,
2
7 ~,ppm
PMR spectra (360 MHz) for solutions of alkylcarbazole fractions of Nibel' crude oil: lower spectrum - in CCI~+CDCI~ (2: 1), upper spectrum - in C~D6. Intensity is twice as great for the resonance region of aromatic H atoms (6.5-8.5 ppm) than for resonance region of aliphatic H atoms (0.5-3.5 ppm). We carried out a preliminary PMR study of alkylcarbazole fractions (the preliminary study showed that aikyl- and benzocarbazole fractions are best a~nalysed separately) isolated from 320°--430°C distillates of two crude oils (see the Experimental section) in an inert solvent (CCI 4 and CDCI3 mixtures) and in a magnetically anisetropic solvent capable of forming hydrogen bonds (C6D6). The spectra of both fractions are roughly identical. In contrast to published spectra of fractions of petroleum hydrocarbons and resins (e.g. [10]), in the spectra obtained it is possible
Use
of IH NMR spectroscopy to study petroleum alkylcarbazoles
229
to distinguish a large number of completely or partially resolved groups of signals differing in position sometimes by less than 0"05 ppm (Figure). The form of the spectrum depends considerably on the nature of the solvent, and this can theoretically be used for analytical purposes. Thus the potential information content of PMR for GSA of petroleum alkylcarbazoles is very great. However, for fractions in a CCI4 + CDCI3 solution, besides standard and slightly arbitrary subdivision of the spectrum into H,, H~, Hp, and H~ regions [10], only two groups of signals can be assigned on the basis of published data. The range d~=2.70--2.85 ppm corresponds to resonance of H atoms of the methyl substituents of carbazole in the fourth position, and the range 2.30-2.65 ppm to resonance in the remaining positions [8]. In this case the first group is overlapped by one other group of signals. According to published data, the possibilities of assigning the signals in the spectra of fractions in C696 are even more limited. To assign the signals in the spectrum of fractions, either an additive scheme for calculating the magnitudes of the chemical shifts is necessary, or a corresponding correlation table, whose creation requires a preliminary study of a representative series of model compounds, must be used. It should be noted that additive schemes for calculating ~ cannot be developed for any type of compound. In the present paper, the characteristics of PMR spectra of carbazole (I) and 1,2,3,4-methylcarbazoles (II-V) in solutions (a CCI4+CDCI3 mixture and C6D6) are determined. The spectral characteristics of di-, tri-, tetra-, and pentamethyland alkyl-substituted carbazoles will be published in subsequent papers. Chemical shifts. The magnitudes of d~ by the H atom of I-V in CCI4+CDCI 4 are given in Table 1. Resonances of protons of the NH groups appear in the form of broadened signals with ~ of about 7.5 ppm (not given in Table 1). Signals in the spectra were assigned on the basis of double homonuclear resonance experiments (irradiation at absorption frequencies of H4, H5, and HMe) with account taken of the magnitude of the chemical shifts and spin-spin interaction constants (SSIC). Thus, the weak-pole multiplet in the spectrum of I evidently corresponds to resonance of H4 [9]. The multiplet of H3 was assigned by IH-{1H4} spin isolation; the signals of HI and H2 were assigned on the basis of an analysis of the I H - {~H4} spectrum in ABX approximation (4J,t x = l . 2 Hz, 3Jnx=7.0 Hz, i.e. H I = A ; H2=B). The signals of protons of unsubstituted rings of II-V were assigned in a similar way. The multiplets of H4 and H5 in the spectrum of II were discerned from the presence of 5JMo,4 (established by means of ~H-{IHMo} spin isolation); in the spectrum of III they were discerned from the absence of 4J2.4. Assignment of the remaining signals for these compounds is obvious. In the spectra of IV and V, the multiplets of the protons of substituted rings were assigned according to the magnitudes of the SSIC with account taken of the fact that 4J2. 4 > 5ji.4 [9] and (for I-IV) 3Ji.2 '-- 8.1 Hz, while 3J2, 3= 7.2 Hz. Data of Table 1 were used to calculate the shifts of the signals of aromatic H atoms when a CH3 group is introduced into different positions of a heterocyclic earbazole system (Table 2). The average magnitudes of the ortho, meta- and para-
230
M.B. SMmNOVe t
m.
effects are -0.195, -0.105, and -0.145 ppm respectively and are similar to these effects for substituted benzenes [11]. The maximum deviations from the average magnitudes of the ortho- and meta-effects are about +0.035 ppm. Introduction of a CH3 group into positions 2 and 3 causes a small increase in the screening of all protons in the unsubstituted ring. The methyl group in position 1 has virtually no effect on the chemical shifts of the signals of H5-H7 and slightly increases screening of H8 (in roughly the same way as the methyl group in position 4). The greatest effect of a CH3 group in an unsubstituted ring is observed for H5 in V, which can be atrributed to spatial interaction of this proton with the substituent. TABLE I. MAGNITUDES OF CHBMICAL SHIFTS OF PROTONS (•, p p m OF T M S ) XN P M R
CARBAZOLB SOLUTIONS IN C C ] , + C D C I s C o m p o u n d I H1 I II
7"342
1II
7"143 7"243 ] 7.203
IV V
(2:
H2
H3
H4
H5
H6
H7
H8
7.340 7.157
7"167 7.097 6"987
8.010 7.862
8.010
7-167 7.164 7.138 7"126 7"173
7"340 7"342 7"299 7"323 7"338
7"342 7.377 7.316 7'325 7"362
7.168 7"235
7'873 7.812
6.938
8.003 7-953 7.971 8.103
SPECTRA OF
Iv/v) Hue
2.553 2'513 2'521 2"863
From the data of Tables 1 and 2 it can be seen that in the aromatic part of the spectra the signals of H4 and H5 are clear, so that min J 4 - m a x J1,,,0"5 ppm. It should be noted that this difference ought to be lower in an acetone solution, since the only significant difference between spectra of I in acetone and a CCI4+CDCI a TABLE 2. EFFECT OF MBTHYL G R O U P SUBSTITUTION O N POSITION OF SIGNALS OF AROMATIC PROTONS
IN P M R SPECTRA OF CARBAZOLE SOLUTIONS IN CC]4-t-CDCi3 (2: Iv/v) Position o f CHs group
HI
I
1-I2
O l
2
-0"199
-
3 4
-0.099 -0"139
-0"172 -0"105
H3
AJ~ (Hs) , p p m * H4 H5 J
H6
[
H7
0070
H8
003
-0.180 -0"137 -0-057 JI-0"029 -0"041
-0.026
--0"229
-0"017 0"020
-0.198 -
-0.039 0-093
-0"041 0-006
-0'017 -0.002
* A3t(Hj)= dtt(Hj) methykarbazole - 6(H7) cat'baz,ole, where I is position of CHa group and ] position of H atom in heterocyclic system of carbzzole.
mixture is shift of H1 resonance (7'49 and 7"34 ppm) [9]. The multiplet of H3 is the most strong-poled in the aromatic part of all the spectra. Although the difference J ~ - J a is roughly equal to the magnitudes of the ortho- and para-effects of CHa groups, so that the absorption regions of HI-H3 overlap, the signals of aromatic protons in the strongest field in spectra of petroleum fractions can be expected to correspond to resonance of Ha and can be used for analytical purposes. The position of signals of CHs groups is similar to that obser,ved in an acetone solution [8]. The results of studying spectra of solutions of I-V in C6D6 are summarized
Use of IH NMR spectroscopy to study petroleum alkylcarbazoles
231
in Tables 3 and 4. The magnitudes of J of protons of N H groups are about 6.7 ppm (not given in Table 1). Methods for assigning the signals are similar to those described above for the first solvent. The average magnitudes of the ortho-, meta-, and paraeffects of CH3 groups are -0.190, -0.045, and - 0 . 0 7 5 ppm respectively; the maximum deviation from the average is 0.04 ppm for ortho- and 0.03 ppm for TABLE 3. MAGNITUDES OF CHEMICAL SHIFTS OF PROTONS (3, p p m OF
TMS)
IN P M R
SPECTRA OF
CARBAZOLE SOLUTIONS IN C 6 D 6
Compound I II 111 IV V
HI I H 2 , 7"041 7.357 - 7.127 6-887 17'011 7'160' !6.964 17.309 ]
H3 7'194 7-170 7"029 6'984
H4 7"979 7.902 7.906 7.803
H5 7'979 8'014 7'990 8"030 8-131
H6 7'194 7.219 7'214 7.224 7.229
H7 7"357 7"387 7"360 7"373 7'379
H8 7'041 7"122 7'066 7'061 7.084
HM, 2.101
2.428 2.433 2.685
* Measured with accuracy of + 0.02 ppm on account of overlapping of signal with signal of solvent.
TABLE 4. EFFECT OF METHYL GROUP SUBSTITUTION ON POSITION OF SIGNALS OF AROMATIC PROTONS IN
Position of Ella group
PMK
SPECTRA OF CARBAZOLE SOLUTIONS IN
C~D6
zM~ (H j), ppm* ] H4 H5 I j-0'077 0-035 ' 0.011 / I --0-073 -0"176 0.051 I 0.152
H6 0.025 0-020 0.030 0.026
H2 ] H3 -0"230 -0"024 -0'154 -0"165 -0.197 t - 0'030 -- 0.077 -0'048 -0.210 HI
H7 I 0.026 0.003 0.016 0.022
H8 0.081 0.025 0.020 0.043
• See footnote to Table 2. t Metmured with accuracy of -t-0.02 ppm.
meta-effects. The effect of a CH3 group on the position of the signals of protons of an unsubstituted ring amounts largely to a small paramagnetic shift (I0 of the 16 values given in Table 4 are equal to 0"025_0.01 ppm). Selective weak-pole shifts are observed for H8 in II and for H5 in V, the absolute magnitude of the shift in the latter case being similar to the average ortho-effect. The benzene-induced shills of resonance frequencies of H atoms are given in Table 5. The main differences between the spectra of I-V in C C I , + C D C I 3 and C6D6 solutions are in the position of the HI and H8 protons of the methyl group in II ( H ~ c - 1) and the N H group. The diamagnetic shift can be used as the criterion for clear assignment of signals in spectra of petroleum fractions. Comparison of the data o f Table 3 and Figure makes it possible to assume that, in the spectra of petroleum fractions in a C6D6 solution, resonance regions of HMe-- 1, HMc -- 8, and HMc -- 2, HM~-- 3, HM,-- 6, and H ~ - 7 combined can be distinguished as well as the absorption region of HM,--4 and HM.--5. The absorption region of H4 and H5 is resolved well in the aromatic part of the spectrum. The resonance region of H7 of unsubstituted rings can also be distinguished.
232
M.B. SMIRNOVet al.
The data given indicate that the P M R method is promising for obtaining information on the distribution of substituents in petroleum alkylcarbazoles. A further study of model compounds is needed for assigning signals in the spectra of petroleum fractions. TABLE 5. MAGNITUDES OF SPECIFIC sHIFTS OF RESONANCE FREQUENCIES OF H ATOMS IN P M R SPECTRA OF CARBAZOLE SOLUTIONS IN BENZENE
Cornpound I
II III IV V
HI -0-301 - 0"256 -0"232 -0"239
H2 0'017 -0.030 -
H3 0"027 0"073 0'042
0.0081
0"074
,~ (Hj), ppm* H4 H5 H6 -0.031 -0"031 0'027 0.040 0"011 0"055 0"033 -
0"046
0"009
0"037 0'059 0"028
0"076 0"096 0"056
H7 ] H8 Hut. 0"017 [ -0"301 0"041 [ -0"255 -0.452 0"061 ] -0"250 - 0"085 0"050 - 0"264 - 0"088 0.041 -0'278 --0"178
* d t l ( H j ) - ~ H , f ) s - 6 ( H j ) = , where di(Hi)t and ~Hs) = sre respectively chemical shifts o f protons Hj, m e ~ u r e d in Iolution of C6D~ and C O 4 + C D C I 3 (2: Iv~v). 1" Me,asutcd with accuracy of _+0.02 ppm.
Spin-spin interaction constants. The measured magnitudes of SSIC correspond to published data for substituted benzenes [9, 12, 13] and carbazole in acetone [9]; no dependence on the nature of the solvent was observed. Similar ortho-constants are roughly the same in all compounds and are as follows, Hz: aJ1.2-~aJT.a---8"l; 3J2,3"3J6,7"~7"2 , 3J3.4-aJs.6~'7"8. The difference in the magnitudes of 3 J r . 2 and aJ'2. a can be used as a diagnostic criterion when assigning signals. The paraconstants (s j , . ,,~_sj5 ' a_~0.75 Hz) and similar recta-constants of unsubstituted rings (4J5, 7~ 1.15 Hz; '*J6, a -~ 1.0 Hz) are also the same. The recta-constants of protons of substituted rings in II-V amounted to 1"0, 1.45, 1"65, and 1.0 Hz respectively. The constants of the protons of methylgroups and aromatic rings are as follows: for II--'*Jue, 2= --0"7 H z a n d 6JMe' 4= --0"6 Hz (the sign of '*J and 6j is adopted in accordance with [12, 14]); for III--'*JMe ' 1=--0"75 Hz and 4Jue ' a = - 0 . 6 Hz; for I V - 4 J m , , , = - 0 . 7 Hz; for V - 4 J u e . 3 = - 0 " 8 Hz and 6JMe' 1=--0"6 Hz; all [sJ 1~<0.3 Hz. The differences in the SSIC of protons of methyl groups in positions 4(]4JMe, 31>1%'e. 11) and 2 ([4Jue ' l[>]4Jm. 31) can be used to assign signals in spectra of polymethyl-substituted carbazoles. EXPERIMENTAL
Petroleum alkylcarbazoles were isolated by the procedure of [5] from 320°-430°C fractions of crude oils of the Pashnya (well 57, depth of occurrence 2640 m) and Nibel' (well 95, depth of occurrence 925 m) fields of the Timano-Pechorsk oil and gas-bearing province. Model methylcarbazoles were synthesized according to [8]. The P M R spectra of solutions of I-V in C6D6 and in a CCI,+CDCI3 mixture (2: Iv/v) were recorded on a WM-250 spectrometer of the Bruker company (West
Use of IH NMR. spectroscopy to study petroleum alkylcarbazoles
233
Germany) with a working frequency of 250 MHz. The recording conditions were as follows: duration of scanning pules 3/~sec (70°); volume of memory for storage 32 K and for reproduction 16 K; machine resolution 0.10--0.15 Hz; pulse repetition time 6.6--10 sec; temperature 303°K; concentration of solutions 1-3 mg/ml. To measure small SSIC, the signal of the drop in free induction was multiplied by the Gaussian function. In monoresonance spectra, chemical shifts were read from the signal of tetramethylsilane (TMS). In spectra of twin resonance IH-{1H}, to eliminate Siegert-Bloch shift the position of the signals was read from the signal of the solvent J~s and converted to a J-scale in accordance with the relation Jt = Jts + js
where Js is the chemical shift of the signal of the solvent from TMS, measured in the monoresonance spectrum. The PMR spectra of petroleum fractions of carbazoles deuterated at the nitrogen atom were recorded on a WH-360 spectrometer of the Bruker company (West Germany) with a working frequency of 360 MHz. The recording conditions were as follows: duration of scanning pulse 5.2/~sec (70°); volume of memory for storage 32 K and for reproduction 16 K; machine resolution 0.23 Hz; LF-filter transmission band 8 kHz, pulse repetition time 10 sec; number of storages 400; temperature 303°K; concentration 14--25 mg/ml; same solvents as for I-V. Replacement of H with D in the N H group of carbazole was carried out in deuteromethanol. The isotopic shifts did not exceed 0.005 ppm. Besides ABX systems, a PANIC program was used to calculate J and SSIC of strongly bound spin systems (a spin system containing a pair of nuclei with ZtVoJ/J<6 was considered to be strongly bound; it was shown that for ,dVoJ/J>6 the corrections on passing from first-order approximation to accurate analysis of the spin system are smaller than the error of measurements). The errors in calculating J were less than 0"001 ppm, the errors in calculating SSIC were +0.1 Hz, and reproducibility when the spectrum was recorded over a period of 1 month was about +0-003 ppm and +0.05 Hz respectively. Determination of J and SSIC of protons of unsubstituted rings was carried out by the following scheme. Values of the parameters used as the initial parameters during accurate analysis of an ABC spin system were calculated from ZH-{1H5} spectra in ABX approximation; the frequencies of 8-10 signals were used in calculations. Total analysis for I-V in CjD6 and for I and V in CCI4+CDCI 3 was carried out in ABCMX approximation (M is an N H group proton, X is H5) and ABCX approximation (for deuterated compounds). Because of inadequate resolution, analysis of the X-part in spectra of solutions of II-IV in CCI4+CDCI3 is possible only when H is replaced by D at the nitrogen. Calculations for them were carried out in ABCX approximation: for NH forms using only the ABC-part of spectra plus magnitudes of Js, and for ND forms with the additional use of the X-part of the spectra. The magnitudes o f J a n d SSIC of aromatic protons substituted rings were calcu-
234
M . B . SMmICOVet al.
lated from spectra of I l l - {IHM,} twin resonance of N H and N D forms. Compounds deuterated at nitrogen were used to determine SSIC of aromatic protons with methyl protons. 4JMe' 2 in II and IV (solution in C6D6) and 4Jue ' i in I I I (in both solvents) were measured from I H - { ~ H 4 } spectra. It proved impossible to measure certain S S I C f o r solutions in C C I 4 + C D C I 3 : SJsH. 4 and sJsH, 5 in I[-1V; 4JMe. z in II; 4J5.7, '~JMe, 2 and sJs. 9 in 1V; 6Jue ' x in V. The following were also not determirted: SJsa. , and SJsa ' s for I I I in C6D6 (in the remaining cases sJNtt ' 4"-0.75 Hz) and ,tj Me, 2 for IV in C6D6 The authors are deeply grateful to Ye.P. Prokof'ev for his continuous assistance with the study.
SUMMARY
1. The potential for using P M R spectroscopy to study the composition and structure of petroleum alkylcarbazoles and primarily to establish the distribution of substituents between positions in the heterocyclic system of carbazole hase been demonstrated. 2. A total analysis has been made of spin systems of protons of carbazoles and 1,2,3,4-melhylcarbazoles. The magnitudes of 8 and nj ( n = 3 - 6 ) and their dependence on the nature of the solvent have been established. REFERENCES
I. V. F. KAM'YANOV, V. S. AKSENOV and V. I. TITOV, Geteroatornnye komponenty neftei (Heteroatornic Components of Crude Oils), p. 130, Nauka, Novosibirsk, 1983 2. L. R. SNYDER, B. E. BUELL and H. E. HOWARD, Anal. Chem 40, 8, 1303, 1968 3. Ye. S. BRODSKII, I. M. LUKASHENKO, A. A. PEROV, A. N. STEPANOV, S. Ye.
KUPRIYANOVA and N. N. KUCHERYAVAYA, Neftekhimiya 19, 6, 880, 1979 4. M. DORBEN, I. IGNATIADIS, I.-M. SHMITTER, P. ARPINO, G. GUICHON, F. H.
TOULHOA and A. HUC, Fuel 63, 565, 1984 5. Ye. B. FROLOV,'N. A. VANYUKOVA and P. I. SANIN, Neftekhirniya 27, 3, 328, 1987 6. I. IGNATIADIS, P. ARPINO and M. DORBON, Rev. de l'Institut Francais du petrole 41, 4, 551, 1986 7. W. CURRUTHERS, J. Chem. Sot:., 17, 2244, 1968 8. M. KUROKI and Y. TSUNASHIMA, J. Heterocyclic Chem. 18, 4, 709, 1981 9. W. BRt~GEL, Handbook of NMR Speatral Parameters, (Ed. Heyden), Vol. 1, 263 pp., Rheine, London-Ptli[edelphia, 1979 10. G. A. KALABIN, V. M. POLONOV, M. B. SMIRNOV, D. F. KUS'HNAREV, T. V. AFONINA and B. A. SMIRNOV, Neftekhimiya 26, 4, 435, 1986 11. L. M. JACKMAN and S. STERNHELL, Application of NMR Spectroscopy in Organic Chemistry, 342 pp., Pergamon Press, Oxford, 1969 12. Kh. GYUNTER, Vvedeniye v kurs spektroskopii YaM'R (Introduction to NMR spectroscopy course), p. 419, Mir, Moscow, 1984 13. M. J. COLLINS, P. M. HATTON, S. STERNHI~.I'. and C. W. TANSEY, Magn. Reson. in Chem. 25, 9, 824, 1987 14. M. BARFIELD, C. J. FALLICK, K. HATA, S. SIT.,RNI4~.IJ. and P. W. WESTERMAN, J. Amer. Chem, Soc. 105, 8, 2178, 1983
~)27
80. Informatsionnyi listok No. 132-83. Repellent dlya zashchity zlzivotnykh ot gnusa ( I n f o r m . tion Leaflet No. 132-83. Repellent for Protecting Animals Against Blood-Sucking Flies), TsNTI, Tyumen, 1983 81. G. Ye. RADTSEVA, N. N. RYAKHOVSKAYA, A. IOI. S H A R I P O V and L. M. ZAGRYATSKAYA) "Fez. dokl. XIV nauchn, sessii po khimii i teidanologii organicheskikh soyedinenii sery i sernistykh neftei (Abstracts of Papers of Fourteenth Scientific Session on Chemistry and Technology of Organic Sulphur Compounds and Sulphur Crude Oils), 103 pp., Zinatne, Riga, 1976
0031-6458188 $10.00+.00 © 1990 Pergamon Prets pie
Petrol. Chem U.S.S.R. Vol. 28, No. 4, pp. 227-234. 1988 Printed in Poland
U S E O F 1H N M R S P E C T R O S C O P Y TO STUDY PETROLEUM ALKYLCARBAZOLES. MONOMETHYLCARBAZOLES* M. B. SMIRNOV, YE. B. FROLOV, N. A. VANYUKOVAand P. I. SANIN A. V. Topchiyev Institute of Petrochemical Synthesis, U.S.SR. Academy of Sciences
(Received 22 April 1988)
TR'E composition and structure of compounds of higher distillates and residual fractions of crude oils ~emain little studied. As is known, neutral nitrogen components (mainly 9-H-alkyl-and benzocarbazoles) predominate in the heavy part of crude oil [I] 5
8
4
tt 9
1
In the first investigations, when studying concentrates high in neutral nitrogen compounds, high-resolution mass spectrometry was used to obtain the MW distributions of alkyl- and benzocarbazoles (see, for example, [2, 3]). The structure of the substituents and their position in the rings have still not been established. A detailed study of petroleum carbazoles has now become possible only by developing selective methods for isolating this type of compound from crude oils [4, 5]. Most attention has been paid to procedures for analysing the individual composition of the fraction. In a number of crude oils, about 20 individual carbazoles (mainly mono- and dimethyl-substituted carbazoles) have been identified [6]. At the same time, formulation of the general problem of total analysis of the individual * Neftekhimiya 28, No. 6, 739-745, 1988
22.8
M.B.
S~tmNov er al.
composition of petroleum carbazoles is virtually impossible in that theoretically there are 210 isomers of C4-alkylcarbazoles alone. Group-structural analysis (GSA) methods must be developed. The main aim of such studies should be to Obtain information on the structure of the substituents and their distribution in the heterocyclic system of the carbazole for fractions as a whole. In practice, such data can be obtained only by means of NMR spectroscopy. However, no procedures of this kind have been developed for any type of heteroatomic compound. N M R spectra of 9-H-alkyl- and bznzocarbazoles have hardly been described [7-9]. Thus the potential of NMR. for solving this problem cannot even be assessed on the basis of published data.
#
7
,
2
7 ~,ppm
PMR spectra (360 MHz) for solutions of alkylcarbazole fractions of Nibel' crude oil: lower spectrum - in CCI~+CDCI~ (2: 1), upper spectrum - in C~D6. Intensity is twice as great for the resonance region of aromatic H atoms (6.5-8.5 ppm) than for resonance region of aliphatic H atoms (0.5-3.5 ppm). We carried out a preliminary PMR study of alkylcarbazole fractions (the preliminary study showed that aikyl- and benzocarbazole fractions are best a~nalysed separately) isolated from 320°--430°C distillates of two crude oils (see the Experimental section) in an inert solvent (CCI 4 and CDCI3 mixtures) and in a magnetically anisetropic solvent capable of forming hydrogen bonds (C6D6). The spectra of both fractions are roughly identical. In contrast to published spectra of fractions of petroleum hydrocarbons and resins (e.g. [10]), in the spectra obtained it is possible
Use
of IH NMR spectroscopy to study petroleum alkylcarbazoles
229
to distinguish a large number of completely or partially resolved groups of signals differing in position sometimes by less than 0"05 ppm (Figure). The form of the spectrum depends considerably on the nature of the solvent, and this can theoretically be used for analytical purposes. Thus the potential information content of PMR for GSA of petroleum alkylcarbazoles is very great. However, for fractions in a CCI4 + CDCI3 solution, besides standard and slightly arbitrary subdivision of the spectrum into H,, H~, Hp, and H~ regions [10], only two groups of signals can be assigned on the basis of published data. The range d~=2.70--2.85 ppm corresponds to resonance of H atoms of the methyl substituents of carbazole in the fourth position, and the range 2.30-2.65 ppm to resonance in the remaining positions [8]. In this case the first group is overlapped by one other group of signals. According to published data, the possibilities of assigning the signals in the spectra of fractions in C696 are even more limited. To assign the signals in the spectrum of fractions, either an additive scheme for calculating the magnitudes of the chemical shifts is necessary, or a corresponding correlation table, whose creation requires a preliminary study of a representative series of model compounds, must be used. It should be noted that additive schemes for calculating ~ cannot be developed for any type of compound. In the present paper, the characteristics of PMR spectra of carbazole (I) and 1,2,3,4-methylcarbazoles (II-V) in solutions (a CCI4+CDCI3 mixture and C6D6) are determined. The spectral characteristics of di-, tri-, tetra-, and pentamethyland alkyl-substituted carbazoles will be published in subsequent papers. Chemical shifts. The magnitudes of d~ by the H atom of I-V in CCI4+CDCI 4 are given in Table 1. Resonances of protons of the NH groups appear in the form of broadened signals with ~ of about 7.5 ppm (not given in Table 1). Signals in the spectra were assigned on the basis of double homonuclear resonance experiments (irradiation at absorption frequencies of H4, H5, and HMe) with account taken of the magnitude of the chemical shifts and spin-spin interaction constants (SSIC). Thus, the weak-pole multiplet in the spectrum of I evidently corresponds to resonance of H4 [9]. The multiplet of H3 was assigned by IH-{1H4} spin isolation; the signals of HI and H2 were assigned on the basis of an analysis of the I H - {~H4} spectrum in ABX approximation (4J,t x = l . 2 Hz, 3Jnx=7.0 Hz, i.e. H I = A ; H2=B). The signals of protons of unsubstituted rings of II-V were assigned in a similar way. The multiplets of H4 and H5 in the spectrum of II were discerned from the presence of 5JMo,4 (established by means of ~H-{IHMo} spin isolation); in the spectrum of III they were discerned from the absence of 4J2.4. Assignment of the remaining signals for these compounds is obvious. In the spectra of IV and V, the multiplets of the protons of substituted rings were assigned according to the magnitudes of the SSIC with account taken of the fact that 4J2. 4 > 5ji.4 [9] and (for I-IV) 3Ji.2 '-- 8.1 Hz, while 3J2, 3= 7.2 Hz. Data of Table 1 were used to calculate the shifts of the signals of aromatic H atoms when a CH3 group is introduced into different positions of a heterocyclic earbazole system (Table 2). The average magnitudes of the ortho, meta- and para-
230
M.B. SMmNOVe t
m.
effects are -0.195, -0.105, and -0.145 ppm respectively and are similar to these effects for substituted benzenes [11]. The maximum deviations from the average magnitudes of the ortho- and meta-effects are about +0.035 ppm. Introduction of a CH3 group into positions 2 and 3 causes a small increase in the screening of all protons in the unsubstituted ring. The methyl group in position 1 has virtually no effect on the chemical shifts of the signals of H5-H7 and slightly increases screening of H8 (in roughly the same way as the methyl group in position 4). The greatest effect of a CH3 group in an unsubstituted ring is observed for H5 in V, which can be atrributed to spatial interaction of this proton with the substituent. TABLE I. MAGNITUDES OF CHBMICAL SHIFTS OF PROTONS (•, p p m OF T M S ) XN P M R
CARBAZOLB SOLUTIONS IN C C ] , + C D C I s C o m p o u n d I H1 I II
7"342
1II
7"143 7"243 ] 7.203
IV V
(2:
H2
H3
H4
H5
H6
H7
H8
7.340 7.157
7"167 7.097 6"987
8.010 7.862
8.010
7-167 7.164 7.138 7"126 7"173
7"340 7"342 7"299 7"323 7"338
7"342 7.377 7.316 7'325 7"362
7.168 7"235
7'873 7.812
6.938
8.003 7-953 7.971 8.103
SPECTRA OF
Iv/v) Hue
2.553 2'513 2'521 2"863
From the data of Tables 1 and 2 it can be seen that in the aromatic part of the spectra the signals of H4 and H5 are clear, so that min J 4 - m a x J1,,,0"5 ppm. It should be noted that this difference ought to be lower in an acetone solution, since the only significant difference between spectra of I in acetone and a CCI4+CDCI a TABLE 2. EFFECT OF MBTHYL G R O U P SUBSTITUTION O N POSITION OF SIGNALS OF AROMATIC PROTONS
IN P M R SPECTRA OF CARBAZOLE SOLUTIONS IN CC]4-t-CDCi3 (2: Iv/v) Position o f CHs group
HI
I
1-I2
O l
2
-0"199
-
3 4
-0.099 -0"139
-0"172 -0"105
H3
AJ~ (Hs) , p p m * H4 H5 J
H6
[
H7
0070
H8
003
-0.180 -0"137 -0-057 JI-0"029 -0"041
-0.026
--0"229
-0"017 0"020
-0.198 -
-0.039 0-093
-0"041 0-006
-0'017 -0.002
* A3t(Hj)= dtt(Hj) methykarbazole - 6(H7) cat'baz,ole, where I is position of CHa group and ] position of H atom in heterocyclic system of carbzzole.
mixture is shift of H1 resonance (7'49 and 7"34 ppm) [9]. The multiplet of H3 is the most strong-poled in the aromatic part of all the spectra. Although the difference J ~ - J a is roughly equal to the magnitudes of the ortho- and para-effects of CHa groups, so that the absorption regions of HI-H3 overlap, the signals of aromatic protons in the strongest field in spectra of petroleum fractions can be expected to correspond to resonance of Ha and can be used for analytical purposes. The position of signals of CHs groups is similar to that obser,ved in an acetone solution [8]. The results of studying spectra of solutions of I-V in C6D6 are summarized
Use of IH NMR spectroscopy to study petroleum alkylcarbazoles
231
in Tables 3 and 4. The magnitudes of J of protons of N H groups are about 6.7 ppm (not given in Table 1). Methods for assigning the signals are similar to those described above for the first solvent. The average magnitudes of the ortho-, meta-, and paraeffects of CH3 groups are -0.190, -0.045, and - 0 . 0 7 5 ppm respectively; the maximum deviation from the average is 0.04 ppm for ortho- and 0.03 ppm for TABLE 3. MAGNITUDES OF CHEMICAL SHIFTS OF PROTONS (3, p p m OF
TMS)
IN P M R
SPECTRA OF
CARBAZOLE SOLUTIONS IN C 6 D 6
Compound I II 111 IV V
HI I H 2 , 7"041 7.357 - 7.127 6-887 17'011 7'160' !6.964 17.309 ]
H3 7'194 7-170 7"029 6'984
H4 7"979 7.902 7.906 7.803
H5 7'979 8'014 7'990 8"030 8-131
H6 7'194 7.219 7'214 7.224 7.229
H7 7"357 7"387 7"360 7"373 7'379
H8 7'041 7"122 7'066 7'061 7.084
HM, 2.101
2.428 2.433 2.685
* Measured with accuracy of + 0.02 ppm on account of overlapping of signal with signal of solvent.
TABLE 4. EFFECT OF METHYL GROUP SUBSTITUTION ON POSITION OF SIGNALS OF AROMATIC PROTONS IN
Position of Ella group
PMK
SPECTRA OF CARBAZOLE SOLUTIONS IN
C~D6
zM~ (H j), ppm* ] H4 H5 I j-0'077 0-035 ' 0.011 / I --0-073 -0"176 0.051 I 0.152
H6 0.025 0-020 0.030 0.026
H2 ] H3 -0"230 -0"024 -0'154 -0"165 -0.197 t - 0'030 -- 0.077 -0'048 -0.210 HI
H7 I 0.026 0.003 0.016 0.022
H8 0.081 0.025 0.020 0.043
• See footnote to Table 2. t Metmured with accuracy of -t-0.02 ppm.
meta-effects. The effect of a CH3 group on the position of the signals of protons of an unsubstituted ring amounts largely to a small paramagnetic shift (I0 of the 16 values given in Table 4 are equal to 0"025_0.01 ppm). Selective weak-pole shifts are observed for H8 in II and for H5 in V, the absolute magnitude of the shift in the latter case being similar to the average ortho-effect. The benzene-induced shills of resonance frequencies of H atoms are given in Table 5. The main differences between the spectra of I-V in C C I , + C D C I 3 and C6D6 solutions are in the position of the HI and H8 protons of the methyl group in II ( H ~ c - 1) and the N H group. The diamagnetic shift can be used as the criterion for clear assignment of signals in spectra of petroleum fractions. Comparison of the data o f Table 3 and Figure makes it possible to assume that, in the spectra of petroleum fractions in a C6D6 solution, resonance regions of HMe-- 1, HMc -- 8, and HMc -- 2, HM~-- 3, HM,-- 6, and H ~ - 7 combined can be distinguished as well as the absorption region of HM,--4 and HM.--5. The absorption region of H4 and H5 is resolved well in the aromatic part of the spectrum. The resonance region of H7 of unsubstituted rings can also be distinguished.
232
M.B. SMIRNOVet al.
The data given indicate that the P M R method is promising for obtaining information on the distribution of substituents in petroleum alkylcarbazoles. A further study of model compounds is needed for assigning signals in the spectra of petroleum fractions. TABLE 5. MAGNITUDES OF SPECIFIC sHIFTS OF RESONANCE FREQUENCIES OF H ATOMS IN P M R SPECTRA OF CARBAZOLE SOLUTIONS IN BENZENE
Cornpound I
II III IV V
HI -0-301 - 0"256 -0"232 -0"239
H2 0'017 -0.030 -
H3 0"027 0"073 0'042
0.0081
0"074
,~ (Hj), ppm* H4 H5 H6 -0.031 -0"031 0'027 0.040 0"011 0"055 0"033 -
0"046
0"009
0"037 0'059 0"028
0"076 0"096 0"056
H7 ] H8 Hut. 0"017 [ -0"301 0"041 [ -0"255 -0.452 0"061 ] -0"250 - 0"085 0"050 - 0"264 - 0"088 0.041 -0'278 --0"178
* d t l ( H j ) - ~ H , f ) s - 6 ( H j ) = , where di(Hi)t and ~Hs) = sre respectively chemical shifts o f protons Hj, m e ~ u r e d in Iolution of C6D~ and C O 4 + C D C I 3 (2: Iv~v). 1" Me,asutcd with accuracy of _+0.02 ppm.
Spin-spin interaction constants. The measured magnitudes of SSIC correspond to published data for substituted benzenes [9, 12, 13] and carbazole in acetone [9]; no dependence on the nature of the solvent was observed. Similar ortho-constants are roughly the same in all compounds and are as follows, Hz: aJ1.2-~aJT.a---8"l; 3J2,3"3J6,7"~7"2 , 3J3.4-aJs.6~'7"8. The difference in the magnitudes of 3 J r . 2 and aJ'2. a can be used as a diagnostic criterion when assigning signals. The paraconstants (s j , . ,,~_sj5 ' a_~0.75 Hz) and similar recta-constants of unsubstituted rings (4J5, 7~ 1.15 Hz; '*J6, a -~ 1.0 Hz) are also the same. The recta-constants of protons of substituted rings in II-V amounted to 1"0, 1.45, 1"65, and 1.0 Hz respectively. The constants of the protons of methylgroups and aromatic rings are as follows: for II--'*Jue, 2= --0"7 H z a n d 6JMe' 4= --0"6 Hz (the sign of '*J and 6j is adopted in accordance with [12, 14]); for III--'*JMe ' 1=--0"75 Hz and 4Jue ' a = - 0 . 6 Hz; for I V - 4 J m , , , = - 0 . 7 Hz; for V - 4 J u e . 3 = - 0 " 8 Hz and 6JMe' 1=--0"6 Hz; all [sJ 1~<0.3 Hz. The differences in the SSIC of protons of methyl groups in positions 4(]4JMe, 31>1%'e. 11) and 2 ([4Jue ' l[>]4Jm. 31) can be used to assign signals in spectra of polymethyl-substituted carbazoles. EXPERIMENTAL
Petroleum alkylcarbazoles were isolated by the procedure of [5] from 320°-430°C fractions of crude oils of the Pashnya (well 57, depth of occurrence 2640 m) and Nibel' (well 95, depth of occurrence 925 m) fields of the Timano-Pechorsk oil and gas-bearing province. Model methylcarbazoles were synthesized according to [8]. The P M R spectra of solutions of I-V in C6D6 and in a CCI,+CDCI3 mixture (2: Iv/v) were recorded on a WM-250 spectrometer of the Bruker company (West
Use of IH NMR. spectroscopy to study petroleum alkylcarbazoles
233
Germany) with a working frequency of 250 MHz. The recording conditions were as follows: duration of scanning pules 3/~sec (70°); volume of memory for storage 32 K and for reproduction 16 K; machine resolution 0.10--0.15 Hz; pulse repetition time 6.6--10 sec; temperature 303°K; concentration of solutions 1-3 mg/ml. To measure small SSIC, the signal of the drop in free induction was multiplied by the Gaussian function. In monoresonance spectra, chemical shifts were read from the signal of tetramethylsilane (TMS). In spectra of twin resonance IH-{1H}, to eliminate Siegert-Bloch shift the position of the signals was read from the signal of the solvent J~s and converted to a J-scale in accordance with the relation Jt = Jts + js
where Js is the chemical shift of the signal of the solvent from TMS, measured in the monoresonance spectrum. The PMR spectra of petroleum fractions of carbazoles deuterated at the nitrogen atom were recorded on a WH-360 spectrometer of the Bruker company (West Germany) with a working frequency of 360 MHz. The recording conditions were as follows: duration of scanning pulse 5.2/~sec (70°); volume of memory for storage 32 K and for reproduction 16 K; machine resolution 0.23 Hz; LF-filter transmission band 8 kHz, pulse repetition time 10 sec; number of storages 400; temperature 303°K; concentration 14--25 mg/ml; same solvents as for I-V. Replacement of H with D in the N H group of carbazole was carried out in deuteromethanol. The isotopic shifts did not exceed 0.005 ppm. Besides ABX systems, a PANIC program was used to calculate J and SSIC of strongly bound spin systems (a spin system containing a pair of nuclei with ZtVoJ/J<6 was considered to be strongly bound; it was shown that for ,dVoJ/J>6 the corrections on passing from first-order approximation to accurate analysis of the spin system are smaller than the error of measurements). The errors in calculating J were less than 0"001 ppm, the errors in calculating SSIC were +0.1 Hz, and reproducibility when the spectrum was recorded over a period of 1 month was about +0-003 ppm and +0.05 Hz respectively. Determination of J and SSIC of protons of unsubstituted rings was carried out by the following scheme. Values of the parameters used as the initial parameters during accurate analysis of an ABC spin system were calculated from ZH-{1H5} spectra in ABX approximation; the frequencies of 8-10 signals were used in calculations. Total analysis for I-V in CjD6 and for I and V in CCI4+CDCI 3 was carried out in ABCMX approximation (M is an N H group proton, X is H5) and ABCX approximation (for deuterated compounds). Because of inadequate resolution, analysis of the X-part in spectra of solutions of II-IV in CCI4+CDCI3 is possible only when H is replaced by D at the nitrogen. Calculations for them were carried out in ABCX approximation: for NH forms using only the ABC-part of spectra plus magnitudes of Js, and for ND forms with the additional use of the X-part of the spectra. The magnitudes o f J a n d SSIC of aromatic protons substituted rings were calcu-
234
M . B . SMmICOVet al.
lated from spectra of I l l - {IHM,} twin resonance of N H and N D forms. Compounds deuterated at nitrogen were used to determine SSIC of aromatic protons with methyl protons. 4JMe' 2 in II and IV (solution in C6D6) and 4Jue ' i in I I I (in both solvents) were measured from I H - { ~ H 4 } spectra. It proved impossible to measure certain S S I C f o r solutions in C C I 4 + C D C I 3 : SJsH. 4 and sJsH, 5 in I[-1V; 4JMe. z in II; 4J5.7, '~JMe, 2 and sJs. 9 in 1V; 6Jue ' x in V. The following were also not determirted: SJsa. , and SJsa ' s for I I I in C6D6 (in the remaining cases sJNtt ' 4"-0.75 Hz) and ,tj Me, 2 for IV in C6D6 The authors are deeply grateful to Ye.P. Prokof'ev for his continuous assistance with the study.
SUMMARY
1. The potential for using P M R spectroscopy to study the composition and structure of petroleum alkylcarbazoles and primarily to establish the distribution of substituents between positions in the heterocyclic system of carbazole hase been demonstrated. 2. A total analysis has been made of spin systems of protons of carbazoles and 1,2,3,4-melhylcarbazoles. The magnitudes of 8 and nj ( n = 3 - 6 ) and their dependence on the nature of the solvent have been established. REFERENCES
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KUPRIYANOVA and N. N. KUCHERYAVAYA, Neftekhimiya 19, 6, 880, 1979 4. M. DORBEN, I. IGNATIADIS, I.-M. SHMITTER, P. ARPINO, G. GUICHON, F. H.
TOULHOA and A. HUC, Fuel 63, 565, 1984 5. Ye. B. FROLOV,'N. A. VANYUKOVA and P. I. SANIN, Neftekhirniya 27, 3, 328, 1987 6. I. IGNATIADIS, P. ARPINO and M. DORBON, Rev. de l'Institut Francais du petrole 41, 4, 551, 1986 7. W. CURRUTHERS, J. Chem. Sot:., 17, 2244, 1968 8. M. KUROKI and Y. TSUNASHIMA, J. Heterocyclic Chem. 18, 4, 709, 1981 9. W. BRt~GEL, Handbook of NMR Speatral Parameters, (Ed. Heyden), Vol. 1, 263 pp., Rheine, London-Ptli[edelphia, 1979 10. G. A. KALABIN, V. M. POLONOV, M. B. SMIRNOV, D. F. KUS'HNAREV, T. V. AFONINA and B. A. SMIRNOV, Neftekhimiya 26, 4, 435, 1986 11. L. M. JACKMAN and S. STERNHELL, Application of NMR Spectroscopy in Organic Chemistry, 342 pp., Pergamon Press, Oxford, 1969 12. Kh. GYUNTER, Vvedeniye v kurs spektroskopii YaM'R (Introduction to NMR spectroscopy course), p. 419, Mir, Moscow, 1984 13. M. J. COLLINS, P. M. HATTON, S. STERNHI~.I'. and C. W. TANSEY, Magn. Reson. in Chem. 25, 9, 824, 1987 14. M. BARFIELD, C. J. FALLICK, K. HATA, S. SIT.,RNI4~.IJ. and P. W. WESTERMAN, J. Amer. Chem, Soc. 105, 8, 2178, 1983