Vibrational spectroscopic studies and ab initio calculations of 2-cyanophenylisocyanid dichloride

Spectrochimica Acta Part A 67 (2007) 1055–1059

Vibrational spectroscopic studies and ab initio calculations of 2-cyanophenylisocyanid dichloride Hema Tresa Varghese a,∗ , C. Yohannan Panicker b , Daizy Philip c , Pavel Pazdera d a

Department of Physics, Fatima Mata National College, Kollam 691 001, Kerala, India Department of Physics, TKM College of Arts and Science, Kollam 691 005, Kerala, India c Department of Physics, Mar Ivanios College, Nalanchira, Trivandrum 695 015, Kerala, India d Department of Organic Chemistry, Faculty of Science, Masaryk University, CZ-611 37 Brno, Czech Republic b

Received 26 May 2006; accepted 2 August 2006

Abstract FT-Raman and FT-IR spectra of 2-cyanophenylisocyanid dichloride were recorded and analyzed. The vibrational frequencies of the title compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. The prepared compound was identified by NMR and mass spectra. © 2006 Elsevier B.V. All rights reserved. Keywords: FT-Raman; FT-IR; HF ab initio calculation; Cyano

1. Introduction N-(2-Cyanophenyl)chloromethanimidoyl chloride can be used as a suitable starting compound for the domino-syntheses of fused pyrimidine and quinazoline skeletons and their precursors, respectively [1,2]. Pazdera et al. [1,2] preprared N-(2-cyanophenyl) chloromethanimidoyl chloride from 2cyanophenylisothiocyanate [3] or from N-(-2-cyanophenyl) formamide. Ab initio quantum mechanical method is at present widely used for simulating IR spectrum. Such simulations are indispensable tools to perform normal coordinate analysis so that modern vibrational spectroscopy is unimaginable without involving them. In the present study, the FT-IR, Raman and theoretical calculations of the wavenumber values of the title compound are reported.

spectrum the emission of the Nd: Yag laser was used, excitation wavelength 1064 nm, maximal power 500 mV, measurement on solid sample. 3. Preparation of the compound N-(2-cyanophenyl)chloromethanimidoyl chloride 3.1. Procedure A 2-Cyanophenylisothiocyanate [3] (24.00 g, 0.15 mol) was dissolved in dry chloroform (50 ml) at room temperature under stirring. Sulfuryl chloride (24 ml, 0.30 mol) was added. The reaction mixture was heated under reflux for 48 h, excess sulfuryl chloride and solvent were removed on a vacuum evaporator and the crude product was crystallized from dry cyclohexane.

2. Experimental

3.2. Procedure B

The FT-IR spectrum (Fig. 1) was recorded using a Genesis (Unicam Mattson) spectrometer in KBr pellets. The FT-Raman spectrum (Fig. 2) was obtained on a Bruker Equinox 55/s spectrometer with FRA Raman socket, 106/s. For a excitation of the

N-(2-Cyanophenyl)formamide (2.90 g, 20 mmol) was mixed with thionyl chloride (20 ml) at 0–5 ◦ C. After 20 h at 0–5 ◦ C sulfuryl chloride (2.6 g, 20 mmol) was added dropwise. The reaction mixture was refluxed for 1 h then concentrated in vacuo. The crude product was suspended in chloroform. The suspension was filtered through silica and the resulting filtrate evaporated in vacuo to yield a product that was crystallized from dry cyclohexane.

∗

Corresponding author. E-mail address: h [email protected] (H.T. Varghese).

1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2006.08.045

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Fig. 1. FT-IR spectrum.

3.3. Procedure C Fig. 3. Optimized geometry.

A solution of 2-cyanophenylisothiocyanate (30.0 g, 0.19 mol) in dry chloroform (50 ml) was saturated with gaseous chlorine (28.0 g, 0.40 mol) with stirring at room temperature for 3 h. Chloroform and sulfur dichloride were stripped off on a vacuum evaporator and the product was crystallized from dry cyclohexane. Yield (A) 22.0 g (73%); yield (B) 2.0 g (51%); yield (C) 28.5 g (75%). m.p. 62–64 ◦ C; for C8 H4 Cl2 N2 (199.04) calculated: 48.28% C, 2.03% H, 14.07% N, 35.62% Cl; found: 48.02% C, 1.92% H, 14.14% N, 35.30% Cl; FT-IR, wavenumber (cm−1 ): 2200 (CN), 1650 (C N), 1480 (C C), 890 (C–Cl); 1 H NMR (CDCl ) d: 7.69–7.68 (1H, m, ArH). 7.63–7.59 (1H, m, 3 ArH), 7.32–7. 29 (1H, m, ArH), 7.13–7.12 (1H, m, ArH); 13 H NMR (CDCl3 ) d: 147.58 (Cq), 141.54 (Cq), 133.54 (CHAr), 133.26 (CHAr), 126.02 (CHAr), 121.20 (CHAr), 116.09 (CN), 105.92 (Cq). Mass spectrum, m/z (Ir/%): 200 (16), 198 (25), 165 (37), 163 (100), 102 (25).

predict the molecular structure and vibrational wavenumber values. Molecular geometry were fully optimized by Berny’s optimization algorithm using redundant internal coordinates. Harmonic wavenumber values were calculated using the analytic second derivatives to confirm the convergence to minima on the potential surface. The wavenumber values computed at the Hartree-Fock level contain known systematic errors due to the negligence of electron correlation [5]. We therefore, have used the scaling factor value of 0.8929 for HF/6-31G* basis set. Parameters corresponding to optimized geometry of the title compound (Fig. 3) is given in Table 1. The absence of imaginary values of wavenumbers on the calculated vibrational spectrum confirms that the structure deduced corresponds to minimum energy. In total there are 42 vibrations from 3041 to 13 cm−1 . The assignments of the calculated wavenumbers is aided by the animation option of MOLEKEL program, which gives a visual presentation of vibrational modes [6,7].

4. Computational details

5. Results and discussion

Calculations of the title compound were carried out with Gaussian03 program [4] using the HF/6-31G* basis set to

The observed Raman and IR bands with their relative intensities and calculated wavenumbers and assignments are

Fig. 2. FT-Raman spectrum.

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Table 1 Optimized geometrical parameters of 2-cyanophenylisocyanid dichloride, atom labeling is according to Fig. 3 ´˚ Bond lengths (A) R(1,2) R(1,6) R(1,7) R(2,3) R(2,8) R(3,4) R(3,9) R(4,5) R(4,10) R(5,6) R(5,11) R(6,12) R(8,14) R(9,13) R(14,15) R(14,16)

Bond angle (◦ ) 1.3863 1.3829 1.0738 1.3936 1.406 1.3921 1.4429 1.38 1.0739 1.3872 1.0739 1.0748 1.2286 1.1361 1.7213 1.7361

A(2,1,6) A(2,1,7) A(6,1,7) A(1,2,3) A(1,2,8) A(3,2,8) A(2,3,4) A(2,3,9) A(4,3,9) A(3,4,5) A(3,4,10) A(5,4,10) A(4,5,6) A(4,5,11) A(6,5,11) A(1,6,5) A(1,6,12) A(5,6,12) A(8,14,15) A(8,14,16) A(15,14,16) L(2,8,14,16,−1) L(3,9,13,2,−1) L(2,8,14,16,−2) L(3,9,13,2,−2)

given in Table 2. In making assignments we have been helped by the published studies on selected organic structures [8], selected benzene derivatives [9] and Silverstein and Webster [10]. The modes are numbered as suggested by Miller [11]. Nitrogen compounds featuring triple or cumulated double bonds, such as cyanides or nitriles (–C N) and cyanates –O–(C N), all provide a unique spectrum, typically with a single, normally intense absorption at 2280–2200 cm−1 (for cyano compounds) and 2285–1990 cm−1 (for cyanates, isocyanates and thiocyanates) [8,12]. In the present case the stretching mode υC N is observed at 2229 cm−1 in the IR spectrum and at 2230 cm−1 in the Raman spectrum. The calculated value for this mode is 2328 cm−1 . Double bonded nitrogen group, imino C N– exhibits absorption close to the carboxyl (C O) and alkene (C C) double bond stretching region 1690–1590 cm−1 [8,12]. For the title compound the stretching mode υC N is observed in the Raman spectrum at 1675 and at 1744 cm−1 theoretically. The deviation of the calculated wavenumber in the HF calculation for this mode can be attributed to the under estimation of the large degree of ␲-electron delocalization due to conjugation in the molecule. Medium to weak absorption bands for the unconjugated C–N linkage in primary, secondary and tertiary aliphatic amines appear in the region of 1250–1020 cm−1 [10]. The vibrations responsible for these bands involve C–N stretching couples with the stretching of adjacent bonds in the molecules. The position of absorption in this region depends on the class of amine and the pattern of substitution on the ␣carbon. Aromatic amines display strong C–N stretching absorp-

Dihedral angle (◦ ) 119.9686 119.2145 120.8163 119.575 119.7212 120.5477 119.9326 120.5537 119.5125 120.3256 119.0208 120.6536 119.4543 120.0925 120.4528 120.7353 119.2981 119.9663 120.6246 126.0858 113.289 124.5731 180.8828 179.8918 180.7604

D(6,1,2,3) D(6,1,2,8) D(7,1,2,3) D(7,1,2,8) D(2,1,6,5) D(2,1,6,12) D(7,1,6,5) D(7,1,6,12) D(1,2,3,4) D(1,2,3,9) D(8,2,3,4) D(8,2,3,9) D(1,2,14,15) D(1,2,14,16) D(3,2,14,15) D(3,2,14,16) D(2,3,4,5) D(2,3,4,10) D(9,3,4,5) D(9,3,4,10) D(3,4,5,6) D(3,4,5,11) D(10,4,5,6) D(10,4,5,11) D(4,5,6,1) D(4,5,6,12) D(11,5,6,1) D(11,5,6,12)

−1.101 −176.5857 178.6264 3.1417 0.5694 −179.6427 −179.1536 0.6343 1.0142 −179.3735 176.4609 −3.9268 100.8404 −78.487 −103.5294 77.1432 −0.392 179.6689 179.9917 0.0526 −0.1459 −179.8907 179.7922 0.0474 0.059 −179.7275 179.8028 0.0163

tion in 1342–1266 cm−1 region [10,13]. The absorption appears at higher frequencies than the corresponding absorption of aliphatic amines because the force constant of the C–N bond is increased by resonance with the ring. Louran et al. [14] reported a value at ∼1220 cm−1 for υCN for poly aniline. For the title compound the υCN mode is observed at 1203 cm−1 in the IR spectrum and at 1208 cm−1 theoretically. The aliphatic CCl bonds absorb at 830–560 cm−1 [13] and putting more than one chlorine on a carbon raises the CCl frequency [13]. CCl2 stretching mode is reported at around 738 cm−1 for dichloromethane and scissoring mode δCCl2 at around 284 cm−1 [9,13]. Pazdera et al. [1,2] reported the CCl stretching mode at 890 cm−1 . For the title compound the band seen at 870 cm−1 in the IR spectrum, 877 cm−1 in the Raman spectrum are assigned as the CCl stretching vibration. Theoretically this mode is found to be at 882 cm−1 . The CH stretching modes are expected in the region 3000–3120 cm−1 [8]. The calculated values are 3041, 3034, 3026 and 3014 cm−1 . These vibrations are observed at 3063 cm−1 in the IR spectrum and at 3088, 3072, 3038, 3000 cm−1 in the Raman spectrum. The benzene ring possess six ring stretching vibrations, of which the four with the highest wavenumbers (16a, 16b, 13a, 13b) occurring respectively near 1600, 1580, 1490, 1440 cm−1 are good group vibrations [8]. With heavy substituents the bands tend to shift to somewhat lower values. The bands observed at 1641, 1578, 1481 cm−1 in the IR spectrum and at 1637, 1591, 1485, 1445 cm−1 in the Raman spectrum are assigned to ring

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Table 2 Calculated vibrational wave numbers, measured infrared and Raman band positions and assignments for 2-cyanophenylisocyanid dichloride υcalculated (cm−1 )

υIR (cm−1 )

υRaman (cm−1 )

Assignments

3041 3034 3026 3014 2328 1744 1610 1581 1480 1440 1265 1208 1183 1161 1086 1077 1018 1007 973 929 882 817 771 741 714 610 606 591 562 550 486 465 390 383 338 253 228 160 126 75 67 13

3063 w

3088 m 3072 s 3038 w 3000 w 2230 vvs 1675 w 1637 vs 1591 vs 1485 w 1445 w 1277 w

υCH 12a υCH 1,12a υCH 12b υCH 5 υC N υC N υPh 16b υPh 16a υPh 13b υPh 13a υPh 9 υCN, δCH δCH 10 δCH 10 υCX(X) 17b υCX(X) δCH 6, 14b υPh 2 γCH 7 γCH 19b υCCl γCH 19a γCH 4 γPh 8,18b γPh, δPh(X) 18b δPh 18a γPh γPh γPh(X), δPh(X) δPh(X), γPh(X) γPh(X), δPh(X) 20a γPh(X) 15a γPh 15a δPh(X) 15a,15b δCX(X) 15a,15b δCX(X) 15a,14a δPh(X), γCX(X) 14a,11a δCX(X) 17a,11a τring 11b τring τring τCCl2

2229 m 1641 vs 1578 m 1481 m 1275 m 1203 w

1188 w 1166 s 1094 wbr 1028 vs

910 vvs 870 w 768 s

635 m

554 m

961 w 913 w 877 w 837 w 786 s 742 wsh 635 w 600 m 580 m 556 w 547 m 490 m 469 w 390 w 378 m 336 m 265 m 248 w 170 m

υ: stretching, δ: in-plane deformation, γ: out-of-plane deformation, τ: torsion, br: broad, v: very, m: medium, s: strong, w: weak, sh: shoulder, X: substituent sensitive, Ph: phenyl; subscript—a: asymmetric, s: symmetric.

stretching modes. The calculated values for these modes are 1610, 1581, 1480 and 1440 cm−1 . In ortho-disubstitution the role of vibration 9 could be rather different from that played in p- and m-disubstitution, since the change in the direction of the main symmetry axis results in the total symmetry of the vibration. This means that the band corresponding to the vibration might be very strong both in the IR and Raman spectrum. Kohlrausch [15] in his fundamental Raman studies of benzene derivatives established a frequency between 1250 and 1290 cm−1 , more or less independent of substitution in ortho disubstituted benzenes. The fifth ring stretching vibration υPh 9 is active near 1315 ± 65 cm−1 , a region which overlaps

strongly that of the δCH mode [8]. The band at ∼1275 cm−1 in both spectra is assigned as υPh9 mode for the title compound. Theoretical calculation gives this mode at 1265 cm−1 . In ortho-disubstitution vibrations 2 and 6 are substitutent sensitive [9]. When both of the substituents are heavy, the vibrations 2 and 6 couple but weakly with the C–X stretching vibrations and both frequencies are increasing as compared to corresponding frequencies of benzene [9]. Substituent sensitive modes are assigned at 1086 and 1077 cm−1 theoretically. The sixth ring stretching mode or ring breathing mode υPh2 appears as a weak band near 1000 cm−1 in mono, 1,3 di and 1,3,5 trisubstituted benzenes [8]. In the other wise substituted benzene, however, this vibration is substituent sensitive and difficult to distinguish from the ring in-plane deformation δCH 6 [8]. The band at 1007 cm−1 given by HF calculation is assigned as υPh2 mode. No bands are experimentally observed for the title compound. For benzenes δCH vibrations are seen in the range 1230–1280 cm−1 and 1170–1000 cm−1 [8]. We have observed theoretical values at 1208, 1183, 1161 and 1018 cm−1 .The bands at 1188, 1166, 1028 cm−1 in the Raman spectrum and at 1203 cm−1 in the IR spectrum are assigned as δCH modes. The mode at 1208 cm−1 is not pure but contains significant contribution form υCN mode. The out-of-plane CH deformation bands γCH are expected in the range 740–990 cm−1 [8]. As seen from Table 2, the ab initio calculation give wavenumbers at 973, 929, 817 and 771 cm−1 . The bands 910, 768 cm−1 in the IR spectrum and 961, 913, 837 and 786 cm−1 in the Raman spectrum are assigned to γCH modes. In the case of 1,2 disubstituted benzene only one strong absorption in the region 755 ± 35 cm−1 is observed and is due to γCH [8]. The strong bands observed at 768 cm−1 in the IR spectrum and 786 cm−1 in the Raman spectrum are assigned to this mode. For the title compound the γPh mode 8 at 742 cm−1 give rise to a weak shoulder band on the γCH band at 786 cm−1 [8]. In o-disubstitution the in-phase mode is obtained from vibration 14a and the out-of-phase one is related to vibration 9a. [9]. Nordheim and Sponer [16] assigned frequencies 199 and 240 cm−1 to CCl in-plane and out-of-plane vibration in the Raman spectrum of o-dichlorobenzene. In o-disubstitution vibration 14a corresponding to the in-phase mode appears between 250 and 450 cm−1 [9]. Vibration 17a corresponding to the out-of-phase mode is found in the frequency interval 135–330 cm−1 [9]. The line of this vibration in the Raman spectrum is generally more intense than the line of vibration 14a. In the case of two heavy substituents the frequency of the vibrational pair 18 increases in o-disubstitution because they are coupled to the in-phase and opposite phase C-heavy stretching vibrations. The splitting of the frequencies due to the coupling is again greater in vibration 18b, which has greater amplitudes in the place of the substitution and therefore in o-disubstitution the frequency of the mode 18b is greater than that of 18a. Shurvell et al. [17] assigned 18a and 18b bands to 703 and 643 cm−1 in the spectrum of o-dibromobenzene. The substituent sensitive vibrations δPh(X) and γPh(X) are seen at 228 and 562 cm−1 [8]. These modes are not pure but contains significant contribution from other modes also. All

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the carbon-carbon bond lengths in the benzene ring lie in ˚ and CH bond lengths in the range the range 1.38–1.3936 A ˚ 1.0738–1.0748 A . Here for the title compound, benzene is a regular hexagon with bond lengths somewhere in between the ˚ and a double (1.33 A) ˚ bond normal values for a single (1.54 A) [18]. Acknowledgements C. Yohannan Panicker (Teacher Fellowship) and Hema Tresa Varghese (minor research grant) would like to thank the University Grants Commission, India.

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