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Vibrational spectroscopic studies and ab initio calculations of sulfanilamide
Spectrochimica Acta Part A 65 (2006) 155–158
Vibrational spectroscopic studies and ab initio calculations of sulfanilamide Hema Tresa Varghese a , C. Yohannan Panicker b,∗ , Daizy Philip b a
b
Department of Physics, Fatima Mata National College, Kollam, Kerala 691001, India Department of Physics, Mar Ivanios College, Nalanchira, Trivandrum, Kerala 695015, India Received 13 September 2005; accepted 20 September 2005
Abstract FT-Raman and FT-IR spectra of sulfanilamide were recorded and analyzed. The vibrational frequencies of the compound have been computed using the Hartree–Fock/6-21G* basis and compared with the experimental values. The assignments of the observed bands were made on the basis of available literature. © 2005 Elsevier B.V. All rights reserved. Keywords: Sulfanilamide; FT-Raman; FT-IR; HF ab initio calculation
1. Introduction Sulfanilamides were successfully employed as effective chemotherapeutic agents for the prevention and cure of bacterial infections in human biological systems [1]. Moreover, sulfadrugs and their complexes, have applications as diuretic, antiglaucoma or antiepileptic drugs among others [2–4]. The sulfanilamides exert their antibacterial action by the competitive inhibition of the enzyme dihydropterase synthetase towards the substrate p-aminobenzoate [5]. Furthermore, metal sulfanilamides get much attention owing to their antimicrobial activity. Extensive study of the crystal structure of three forms of sulfanilamide [6–9] and the characterization of sulfanilamide and its derivative complexes has been reported [10–13]. However, reports of IR and Raman studies on the structures of free sulfanilamide and its derivative complexes are too few. IR spectra of SO2 group in sulfonamide derivatives and related compounds had been reported by Rastelli et al. [14], Narang and Gupta [15] and Blasco et al. [2] had described IR characterization of Cu(II) complexes of sulfanilamide. SO2 vibrations and NH2 modes of amino and sulfonamide group of sulfanilamide had been investigated by Narang and Gupta [15]. In addition to these vibrations, in order to deduce structural differences upon coordination, υSN
vibrations of sulfanilamide had been reported by Blasco et al. [2]. Ab initio quantum mechanical calculations for the assignment of IR spectrum of sulfanilamide had been reported by Topacli and Topacli [16]. In the present study the FT-IR, FT-Raman and theoretical calculations of the frequencies of the title compound are reported. 2. Experimental Sulfanilamide was procured from Sigma–Aldrich, USA. The FT-IR and FT-Raman spectra (Figs. 1 and 2) were recorded using a Bruker IFS 66V FT-IR/FT-Raman spectrometer. 3. Computational details The vibrational frequencies were calculated using Gaussian03 program package [17]. The frequency values computed at the Hartree–Fock level contain known systematic errors due to the negligence of electron correlation [18]. We, therefore, have used the scaling factor value of 0.8929 for HF/6-21G* . Parameters corresponding to optimized geometry of sulfanilamide (Fig. 3) is given in Table 1. 4. Results and discussion
∗
Corresponding author at: Department of Physics, TKM College of Arts and Science, Kollam, Kerala 691005, India. E-mail address: [email protected] (C.Y. Panicker). 1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2005.09.040
In making assignments we have been helped by the published studies on selected organic structures [19], selected benzene
156
H.T. Varghese et al. / Spectrochimica Acta Part A 65 (2006) 155–158 Table 1 Optimized geometrical parameters of sulfanilamide, atom labeling is according to Fig. 3
Fig. 1. FT-IR spectrum in the region 4000–500 cm−1 .
Fig. 2. FT-Raman spectrum in the region 3500–100 cm−1 .
derivatives [20] and Silverstein and Webster [21]. The observed Raman and IR bands with their relative intensities and calculated frequencies and assignments are given in Table 2. The modes are numbered as suggested by Miller [22]. The calculated vibrational spectrum has no imaginary frequencies which helped to confirm that the structure of the title compound deduced following geometry optimization corresponds to energy minimum. In total, there are 51 vibrations from 3490 to 40 cm−1 . NH2 stretching modes of sulfonamide are expected in the region 3230–3390 cm−1 [19] and that of aniline ring in the region 3250–3480 cm−1 [19]. The HF/6-21G* basis ab initio calculations for sulfanilamide shows that these vibrations are located in the range 3345–3490 cm−1 . Topacli and Topacli [16] reported the calculated frequencies in the range 3670–3920 cm−1 for NH2
Fig. 3. Geometry of sulfanilamide molecule.
˚ Bond lengths (A)
Bond angle (◦ )
Dihedral angle (◦ )
C1 –C2 , 1.3742 C1 –C6 , 1.3991 C1 –H7 , 1.0717 C2 –C3 , 1.3855 C2 –H8 , 1.0710 C3 –C4 , 1.3855 C3 –S12 , 1.7340 C4 –C5 , 1.3742 C4 –H9 , 1.0710 C5 –C6 , 1.3991 C5 –H10 , 1.0717 C6 –N11 , 1.3657 N11 –H18 , 0.9953 N11 –H19 , 0.9953 S12 –O13 , 1.4343 S12 –O14 , 1.4343 S12 –N15 , 1.6124 N15 –H16 , 0.9986 N15 –H17 , 0.9986
A(2, 1, 6), 120.7023 A(2, 1, 7), 119.8397 A(6, 1, 7), 119.4529 A(1, 2, 3), 120.5382 A(1, 2, 8), 120.1465 A(3, 2, 8), 119.3010 A(2, 3, 4), 119.3042 A(2, 3, 12), 120.3465 A(4, 3, 12), 120.3467 A(3, 4, 5), 120.5385 A(3, 4, 9), 119.3030 A(5, 4, 9), 120.1442 A(4, 5, 6), 120.7020 A(4, 5, 10), 119.8392 A(6, 5, 10), 119.4537 A(1, 6, 5), 118.1914 A(1, 6, 11), 120.9026 A(5, 6, 11), 120.9037 A(6, 11, 18), 121.0323 A(6, 11, 19), 121.0322 A(18, 11, 19), 117.9021 A(3, 12, 13) 107.4256 A(3, 12, 14), 107.4276 A(3, 12, 15), 106.2750 A(13, 12, 14), 122.0505 A(13, 12, 15), 106.3541 A(14, 12, 15), 106.3538 A(12, 15, 16), 119.9256 A(12, 15, 17), 119.9197 A(16, 15, 17), 119.2799
D(6, 1, 2, 3), 0.5095 D(6, 1, 2, 8), −178.1073 D(7, 1, 2, 3), 179.6849 D(7, 1, 2, 8), 1.0681 D(2, 1, 6, 5), 0.6244 D(2, 1, 6, 11), −179.9272 D(7, 1, 6, 5), −178.5542 D(7, 1, 6, 11), 0.8942 D(1, 2, 3, 4), −1.6434 D(1, 2, 3, 12), 178.9508 D(8, 2, 3, 4), 176.985 D(8, 2, 3, 12), −2.4208 D(2, 3, 4, 5), 1.6435 D(2, 3, 4, 9), −176.9829 D(12, 3, 4, 5), −178.9507 D(12, 3, 4, 9), 2.423 D(2, 3, 12, 13), 23.2147 D(2, 3, 12, 14), 156.1741 D(2, 3, 12, 15), −90.3053 D(4, 3, 12, 13), −156.1849 D(4, 3, 12, 14), −23.2255 D(4, 3, 12, 15), 90.2951 D(3, 4, 5, 6), −0.5097 D(3, 4, 5, 10), −179.6839 D(9, 4, 5, 6), 178.1051 D(9, 4, 5, 10), −1.0691 D(4, 5, 6, 1), −0.6242 D(4, 5, 6, 11), 179.9274 D(10, 5, 6, 1), 178.5531 D(10, 5, 6, 11), −0.8953 D(1, 6, 11, 18), −178.6431 D(1, 6, 11, 19), −0.7900 D(5, 6, 11, 18), 0.7903 D(5, 6, 11, 19), 178.6434 D(3, 12, 15, 16), −95.3842 D(3, 12, 15, 17), 95.3977 D(13, 12, 15, 16), 150.3611 D(13, 12, 15, 17), −18.8569 D(14, 12, 15, 16), 18.8726 D(14, 12, 15, 17), −150.3454
stretching modes. The bands corresponding to the δNH2 vibrations belonging to the aniline ring and sulfonamide group are expected in the region 1620 ± 20 and 1565 ± 15 cm−1 , respectively [19]. In IR and Raman spectra δNH2 of aniline is observed at 1629 cm−1 and that of sulfonamide group is observed in the IR spectrum at 1573 cm−1 . The calculated values are 1634 and 1577 cm−1 , respectively, for NH2 group of aniline and sulfonamide. The wagging mode of NH2 of aniline is expected in the range 620 ± 100 cm−1 and NH2 wagg of sulfonamide in the range 690 ± 40 cm−1 [19]. The wagging mode of NH2 group in aniline is observed at 540 cm−1 in the IR spectrum and that of sulfonamide group at 683 cm−1 in the IR spectrum and at 689 cm−1 in the Raman spectrum. Evans [23] reported a frequency at 670 cm−1 and Topacli and Topacli [16] gives 644 cm−1 to the wagging mode of NH2 group in aniline. The torsional NH2 mode of aniline are seen in the range 230 ± 70 cm−1 and torsional mode of NH2 of sulfonamide in
H.T. Varghese et al. / Spectrochimica Acta Part A 65 (2006) 155–158 Table 2 Calculated vibrational wave numbers, measured infrared and Raman band positions and assignments for sulfanilamide υcalculated (cm−1 )
υIR (cm−1 )
3490 3464 3384 3345 3031 3028 3003 3002
3478 s
1634 1583 1577 1541 1501 1427 1346 1333 1270 1200 1195 1143 1127 1096 1048 1043 1002 907 891 865 807 771 687 652 573 571 496 463 432 416 410 388 371 364 355 292 211 177 160 92 40
3375 s 3266 s 3147 w 3086 w 3062 w 3050 w 2683 wbr 2633 wbr 1916 w 1629 s 1595 s 1573 w 1503 s 1440 s 1313 vsbr 1300 m
υRaman (cm−1 )
3371 w 3264 w
3068 w
1629 s 1594 s
1502 w 1315 w 1303 w
1188 m 1147 vs
1157 w 1136 vvs
1096 s
1093 w
1003 w 969 w 900 s
1002 w 967 vw 900 w
837 s 824 s
842 m 822 w 715 w 689 w
683 s 626 m 563 s 540 s
564 w
450 w
400 w 371 w
298 m 226 w 193 w 117 vvs
Assignments υa NH2 (an) υa NH2 (sulfo) υs NH2 (an) υs NH2 (sulfo) υCH 12b υCH 12a υCH 1, 12a υCH 1, 12a, 15b Overtones/combinations Overtones/combinations Overtones/combinations δNH2 (an) 16a υPh 16a, 16b δNH2 (sulfo) 16a, 16b υPh υPh 13a υPh 13b υa SO2 9 δCH 3, 9 υC–N δCH υPh 5, 17a δCH 5, 17a υs SO2 5 δCH δCH 2 γCH γCH δCH 14a γCH 7, 19a υS–N γCH γCH γCH 11a, 18a, 19b δPh(X) 9b, 11a, 18a γPh 8 ωNH2 (sulfo), γPh, 8 δSO2 , δPh, 6, 18b ωSO2 , γPh(X), 6 ωNH2 (an), γPh(X), 20b γPh ρSO2 17b, 20b γPh γPh, τNH2 (sulf) τNH2 (sulf), 15a, 17b, 20a τNH2 (sulf) tNH2 (an), 15a, 17b τNH2 (sulf) τNH2 (sulf) δCSN, 11b, 15a, 17b τNH2 (an), 10 τNH2 (an), 10 τPh, 4 τPh τPh
υ: stretching, δ: in-plane deformation, γ: out-of-plane deformation, br: broad, τ: torsional, t: twisting, v: very, m: medium, s: strong, w: weak, sulf: sulfonamide, an: aniline. Subscripts—a: asymmetric, s: symmetric.
157
the range 355 ± 65 cm−1 [19]. Calculations give frequencies in the range 160–416 cm−1 for this mode as seen in Table 2. At 355, 364 and 388 cm−1 the torsion NH2 sulfonamide vibrations are not pure and contain contributions of phenyl ring modes also. In the Raman spectrum, the bands 298, 226, and 193 cm−1 are assigned as torsion of NH2 . The low frequency vibration at 40 and 92 cm−1 is assigned to the torsional mode of the phenyl ring. The SO2 antisymmetric stretching vibration appears in the region 1330 ± 30 cm−1 and the symmetric counterpart in the region 1160 ± 30 cm−1 both with high intensity [19,21]. The experimentally observed bands at 1313 cm−1 in the IR spectrum and 1315 cm−1 in the Raman spectrum are assigned to the υSO2 asymmetric modes and 1147 cm−1 in the IR spectrum and 1136 cm−1 in the Raman spectrum are assigned to the υSO2 symmetric modes. The calculations give 1346 and 1143 cm−1 as υSO2 asymmetric and υSO2 symmetric modes. Topacli and Topacli [16] assigned 1059 and 883 cm−1 theoretically and 1317 and 1144 cm−1 experimentally as asymmetric and symmetric modes of υSO2 . The SO2 scissors is assigned in the region 570 ± 60 cm−1 and the SO2 wagging vibration near 520 ± 40 cm−1 , both with medium intensity and clearly separated [19]. They are observed at 626 and 563 cm−1 in the IR spectrum of sulfanilamide. The C–S–N deformation is observed at 298 cm−1 in the Raman spectrum [19]. The CH stretching modes are expected in the region 3005–3115 cm−1 [19]. The calculated values are 3031, 3028, 3003 and 3002 cm−1 . These vibrations are observed at 3147, 3086 and 3062 cm−1 in the IR spectrum and at 3068 and 3050 cm−1 in the Raman spectrum with weak intensities. The bands observed at 1595, 1503, 1440 and 1188 cm−1 in the IR spectrum and 1594 and 1502 cm−1 in the Raman spectrum are assigned to ring stretching modes. This result is in agreement with Topacli et al. [16,24] for the strong IR bands at 1597, 1505 and 1440 cm−1 . The calculated values for this mode are 1583, 1541, 1501, 1427 and 1195 cm−1 . Topacli and Topacli [16] reported theoretical values to be at 1773, 1680, 1600, 1354 and 1266 cm−1 . These vibrations are expected in the range 1280–1620 cm−1 [19]. The out-of-plane CH deformation bands γCH are expected in the range 790–990 cm−1 [19]. As seen from Table 2, the ab initio calculations give frequencies at 1048, 1043, 891 and 865 cm−1 . The bands at 969, 837 cm−1 in the IR spectrum and 967, 842 cm−1 in the Raman spectrum are assigned to this mode. According to Topacli and Topacli [16] the experimental values are 1005, 967, 897 cm−1 and the calculated values are 1172, 1010, 973 cm−1 . The δ ring planar deformation modes are observed at 652 and 807 cm−1 theoretically. The bands at 807, 652, 573 and 571 cm−1 are not pure but contain contributions from Ph(X) substituent sensitive vibrations [19]. For 1–4 light heavy disubstituted benzenes δCH vibrations are seen in the range 1225–1315 cm−1 and 995–1190 cm−1 [19]. Topacli and Topacli [16] observed these vibrations at 1340, 1187 cm−1 in the IR spectrum and the theoretical values are 1500 and 1341 cm−1 . We have observed theoretical values at 1333, 1200, 1127, 1096 and 1002 cm−1 . The experimental values are observed at 1300, 1096 and 1003 cm−1 in the IR
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spectrum and at 1303, 1157, 1093 and 1002 cm−1 in the Raman spectrum. The υSN provides a weak to moderate band in the range 905 ± 70 cm−1 [19]. The S–N stretching vibration exhibits a strong band in the IR spectrum and a weak band in the Raman spectrum at 900 cm−1 [19]. Theoretically we have obtained a value 907 cm−1 corresponding to this band. In the spectra of N-substituted 2-thiophenesulfonamides, Arcoria et al. [25] assigned to υSN in the region 900 ± 65 cm−1 . The majority of the investigated secondary sulfonamides were found to give this stretching frequency at 910 ± 35 cm−1 [19]. Acknowledgements C. Yohannan Panicker would like to thank the University Grants Commission, India for awarding a Teacher Fellowship and Hema Tresa Varghese thanks University Grants Commission, India for a minor research grant. References [1] C. Munoz, in: J. Mardones (Ed.), Farmacologia, Intermedica, Buenos Aires, 1979 (Chapter 60). [2] F. Blasco, L. Perello, J. Latorre, J. Borras, S. Garcia-Granda, J. Inorg. Biochem. 61 (1996) 143. [3] S. Ferrer, J. Borras, E. Garcia-Espana, J. Inorg. Biochem. 39 (1990) 297. [4] C.T. Supuran, F. Mincoine, A. Scozzafava, F. Brigenti, G. Mincinone, M.A. Ilies, Eur. J. Med. Chem. 33 (1998) 247. [5] A. Garcia-Raso, J.J. Fiol, S. Rigo, A. Lopez-Lopez, E. Molins, E. Espinosa, E. Borras, G. Alzuet, J. Borras, A. Castineiras, Polyhedron 19 (2000) 991. [6] B.H. Oconnor, E.N. Maslen, Acta Crystallogr. 18 (1965) 363. [7] A.M. O’Connell, E.N. Maslen, Acta Crystallogr. 22 (1967) 134. [8] M. Alleaume, J. Decap, Acta Crystallogr. 19 (1965) 934. [9] M. Alleaume, J. Decap, Acta Crystallogr. 18 (1965) 731.
[10] A. Butt, Pharm. Week. Sci. (1981) 1. [11] A. Butt, in: Sigel (Ed.), Metal Ions in Biological Systems, vol. 16, Marcel Dekker, New York, 1983. [12] A. Butt, J.D. Uitterdijk, H.B. Klasen, Transition Met. Chem. 4 (1979) 285. [13] K.K. Narang, J.K. Gupta, Transition Met. Chem. 2 (1977) 83. [14] A. Rastelli, P.G. Debenede, A. Albasins, G. Vampa, M. Melegari, Farm. Ed. Sci. 29 (1974) 654. [15] K.K. Narang, J.K. Gupta, Indian J. Chem. 13 (1975) 705. [16] C. Topacli, A. Topacli, J. Mol. Struct. 644 (2003) 145. [17] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.U. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian03, Revision C.02, Gaussian Inc., Wallingford, CT, 2004. [18] J.B. Foresman, E. Frisch, Exploring Chemistry with Electronic Structure Methods: A Guide to Using Gaussian, Gaussian, Pittsburgh, PA, 1996. [19] N.P.G. Roeges, A Guide to the Complete Interpretation of Infrared Spectra of Organic Structures, Wiley, New York, 1994. [20] G. Varsanyi, Assignments for Vibrational Spectra of Seven Hundred Benzene Derivatives, Wiley, New York, 1974. [21] R.M. Silverstein, F.X. Webster, Spectrometric Identification of Organic Compounds, 6th ed., Wiley, Asia, 2003. [22] F.A. Miller, J. Raman Spectrosc. 19 (1988) 219. [23] J.C. Evans, Spectrochim. Acta 16 (1960) 428. [24] A. Topacli, B. Kesimli, Spectrosc. Lett. 34 (2001) 513. [25] A. Arcoria, E. Maccarone, G. Musumarra, G. Tomaselli, Spectrochim. Acta 30A (1974) 611.
Vibrational spectroscopic studies and ab initio calculations of sulfanilamide Hema Tresa Varghese a , C. Yohannan Panicker b,∗ , Daizy Philip b a
b
Department of Physics, Fatima Mata National College, Kollam, Kerala 691001, India Department of Physics, Mar Ivanios College, Nalanchira, Trivandrum, Kerala 695015, India Received 13 September 2005; accepted 20 September 2005
Abstract FT-Raman and FT-IR spectra of sulfanilamide were recorded and analyzed. The vibrational frequencies of the compound have been computed using the Hartree–Fock/6-21G* basis and compared with the experimental values. The assignments of the observed bands were made on the basis of available literature. © 2005 Elsevier B.V. All rights reserved. Keywords: Sulfanilamide; FT-Raman; FT-IR; HF ab initio calculation
1. Introduction Sulfanilamides were successfully employed as effective chemotherapeutic agents for the prevention and cure of bacterial infections in human biological systems [1]. Moreover, sulfadrugs and their complexes, have applications as diuretic, antiglaucoma or antiepileptic drugs among others [2–4]. The sulfanilamides exert their antibacterial action by the competitive inhibition of the enzyme dihydropterase synthetase towards the substrate p-aminobenzoate [5]. Furthermore, metal sulfanilamides get much attention owing to their antimicrobial activity. Extensive study of the crystal structure of three forms of sulfanilamide [6–9] and the characterization of sulfanilamide and its derivative complexes has been reported [10–13]. However, reports of IR and Raman studies on the structures of free sulfanilamide and its derivative complexes are too few. IR spectra of SO2 group in sulfonamide derivatives and related compounds had been reported by Rastelli et al. [14], Narang and Gupta [15] and Blasco et al. [2] had described IR characterization of Cu(II) complexes of sulfanilamide. SO2 vibrations and NH2 modes of amino and sulfonamide group of sulfanilamide had been investigated by Narang and Gupta [15]. In addition to these vibrations, in order to deduce structural differences upon coordination, υSN
vibrations of sulfanilamide had been reported by Blasco et al. [2]. Ab initio quantum mechanical calculations for the assignment of IR spectrum of sulfanilamide had been reported by Topacli and Topacli [16]. In the present study the FT-IR, FT-Raman and theoretical calculations of the frequencies of the title compound are reported. 2. Experimental Sulfanilamide was procured from Sigma–Aldrich, USA. The FT-IR and FT-Raman spectra (Figs. 1 and 2) were recorded using a Bruker IFS 66V FT-IR/FT-Raman spectrometer. 3. Computational details The vibrational frequencies were calculated using Gaussian03 program package [17]. The frequency values computed at the Hartree–Fock level contain known systematic errors due to the negligence of electron correlation [18]. We, therefore, have used the scaling factor value of 0.8929 for HF/6-21G* . Parameters corresponding to optimized geometry of sulfanilamide (Fig. 3) is given in Table 1. 4. Results and discussion
∗
Corresponding author at: Department of Physics, TKM College of Arts and Science, Kollam, Kerala 691005, India. E-mail address: [email protected] (C.Y. Panicker). 1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2005.09.040
In making assignments we have been helped by the published studies on selected organic structures [19], selected benzene
156
H.T. Varghese et al. / Spectrochimica Acta Part A 65 (2006) 155–158 Table 1 Optimized geometrical parameters of sulfanilamide, atom labeling is according to Fig. 3
Fig. 1. FT-IR spectrum in the region 4000–500 cm−1 .
Fig. 2. FT-Raman spectrum in the region 3500–100 cm−1 .
derivatives [20] and Silverstein and Webster [21]. The observed Raman and IR bands with their relative intensities and calculated frequencies and assignments are given in Table 2. The modes are numbered as suggested by Miller [22]. The calculated vibrational spectrum has no imaginary frequencies which helped to confirm that the structure of the title compound deduced following geometry optimization corresponds to energy minimum. In total, there are 51 vibrations from 3490 to 40 cm−1 . NH2 stretching modes of sulfonamide are expected in the region 3230–3390 cm−1 [19] and that of aniline ring in the region 3250–3480 cm−1 [19]. The HF/6-21G* basis ab initio calculations for sulfanilamide shows that these vibrations are located in the range 3345–3490 cm−1 . Topacli and Topacli [16] reported the calculated frequencies in the range 3670–3920 cm−1 for NH2
Fig. 3. Geometry of sulfanilamide molecule.
˚ Bond lengths (A)
Bond angle (◦ )
Dihedral angle (◦ )
C1 –C2 , 1.3742 C1 –C6 , 1.3991 C1 –H7 , 1.0717 C2 –C3 , 1.3855 C2 –H8 , 1.0710 C3 –C4 , 1.3855 C3 –S12 , 1.7340 C4 –C5 , 1.3742 C4 –H9 , 1.0710 C5 –C6 , 1.3991 C5 –H10 , 1.0717 C6 –N11 , 1.3657 N11 –H18 , 0.9953 N11 –H19 , 0.9953 S12 –O13 , 1.4343 S12 –O14 , 1.4343 S12 –N15 , 1.6124 N15 –H16 , 0.9986 N15 –H17 , 0.9986
A(2, 1, 6), 120.7023 A(2, 1, 7), 119.8397 A(6, 1, 7), 119.4529 A(1, 2, 3), 120.5382 A(1, 2, 8), 120.1465 A(3, 2, 8), 119.3010 A(2, 3, 4), 119.3042 A(2, 3, 12), 120.3465 A(4, 3, 12), 120.3467 A(3, 4, 5), 120.5385 A(3, 4, 9), 119.3030 A(5, 4, 9), 120.1442 A(4, 5, 6), 120.7020 A(4, 5, 10), 119.8392 A(6, 5, 10), 119.4537 A(1, 6, 5), 118.1914 A(1, 6, 11), 120.9026 A(5, 6, 11), 120.9037 A(6, 11, 18), 121.0323 A(6, 11, 19), 121.0322 A(18, 11, 19), 117.9021 A(3, 12, 13) 107.4256 A(3, 12, 14), 107.4276 A(3, 12, 15), 106.2750 A(13, 12, 14), 122.0505 A(13, 12, 15), 106.3541 A(14, 12, 15), 106.3538 A(12, 15, 16), 119.9256 A(12, 15, 17), 119.9197 A(16, 15, 17), 119.2799
D(6, 1, 2, 3), 0.5095 D(6, 1, 2, 8), −178.1073 D(7, 1, 2, 3), 179.6849 D(7, 1, 2, 8), 1.0681 D(2, 1, 6, 5), 0.6244 D(2, 1, 6, 11), −179.9272 D(7, 1, 6, 5), −178.5542 D(7, 1, 6, 11), 0.8942 D(1, 2, 3, 4), −1.6434 D(1, 2, 3, 12), 178.9508 D(8, 2, 3, 4), 176.985 D(8, 2, 3, 12), −2.4208 D(2, 3, 4, 5), 1.6435 D(2, 3, 4, 9), −176.9829 D(12, 3, 4, 5), −178.9507 D(12, 3, 4, 9), 2.423 D(2, 3, 12, 13), 23.2147 D(2, 3, 12, 14), 156.1741 D(2, 3, 12, 15), −90.3053 D(4, 3, 12, 13), −156.1849 D(4, 3, 12, 14), −23.2255 D(4, 3, 12, 15), 90.2951 D(3, 4, 5, 6), −0.5097 D(3, 4, 5, 10), −179.6839 D(9, 4, 5, 6), 178.1051 D(9, 4, 5, 10), −1.0691 D(4, 5, 6, 1), −0.6242 D(4, 5, 6, 11), 179.9274 D(10, 5, 6, 1), 178.5531 D(10, 5, 6, 11), −0.8953 D(1, 6, 11, 18), −178.6431 D(1, 6, 11, 19), −0.7900 D(5, 6, 11, 18), 0.7903 D(5, 6, 11, 19), 178.6434 D(3, 12, 15, 16), −95.3842 D(3, 12, 15, 17), 95.3977 D(13, 12, 15, 16), 150.3611 D(13, 12, 15, 17), −18.8569 D(14, 12, 15, 16), 18.8726 D(14, 12, 15, 17), −150.3454
stretching modes. The bands corresponding to the δNH2 vibrations belonging to the aniline ring and sulfonamide group are expected in the region 1620 ± 20 and 1565 ± 15 cm−1 , respectively [19]. In IR and Raman spectra δNH2 of aniline is observed at 1629 cm−1 and that of sulfonamide group is observed in the IR spectrum at 1573 cm−1 . The calculated values are 1634 and 1577 cm−1 , respectively, for NH2 group of aniline and sulfonamide. The wagging mode of NH2 of aniline is expected in the range 620 ± 100 cm−1 and NH2 wagg of sulfonamide in the range 690 ± 40 cm−1 [19]. The wagging mode of NH2 group in aniline is observed at 540 cm−1 in the IR spectrum and that of sulfonamide group at 683 cm−1 in the IR spectrum and at 689 cm−1 in the Raman spectrum. Evans [23] reported a frequency at 670 cm−1 and Topacli and Topacli [16] gives 644 cm−1 to the wagging mode of NH2 group in aniline. The torsional NH2 mode of aniline are seen in the range 230 ± 70 cm−1 and torsional mode of NH2 of sulfonamide in
H.T. Varghese et al. / Spectrochimica Acta Part A 65 (2006) 155–158 Table 2 Calculated vibrational wave numbers, measured infrared and Raman band positions and assignments for sulfanilamide υcalculated (cm−1 )
υIR (cm−1 )
3490 3464 3384 3345 3031 3028 3003 3002
3478 s
1634 1583 1577 1541 1501 1427 1346 1333 1270 1200 1195 1143 1127 1096 1048 1043 1002 907 891 865 807 771 687 652 573 571 496 463 432 416 410 388 371 364 355 292 211 177 160 92 40
3375 s 3266 s 3147 w 3086 w 3062 w 3050 w 2683 wbr 2633 wbr 1916 w 1629 s 1595 s 1573 w 1503 s 1440 s 1313 vsbr 1300 m
υRaman (cm−1 )
3371 w 3264 w
3068 w
1629 s 1594 s
1502 w 1315 w 1303 w
1188 m 1147 vs
1157 w 1136 vvs
1096 s
1093 w
1003 w 969 w 900 s
1002 w 967 vw 900 w
837 s 824 s
842 m 822 w 715 w 689 w
683 s 626 m 563 s 540 s
564 w
450 w
400 w 371 w
298 m 226 w 193 w 117 vvs
Assignments υa NH2 (an) υa NH2 (sulfo) υs NH2 (an) υs NH2 (sulfo) υCH 12b υCH 12a υCH 1, 12a υCH 1, 12a, 15b Overtones/combinations Overtones/combinations Overtones/combinations δNH2 (an) 16a υPh 16a, 16b δNH2 (sulfo) 16a, 16b υPh υPh 13a υPh 13b υa SO2 9 δCH 3, 9 υC–N δCH υPh 5, 17a δCH 5, 17a υs SO2 5 δCH δCH 2 γCH γCH δCH 14a γCH 7, 19a υS–N γCH γCH γCH 11a, 18a, 19b δPh(X) 9b, 11a, 18a γPh 8 ωNH2 (sulfo), γPh, 8 δSO2 , δPh, 6, 18b ωSO2 , γPh(X), 6 ωNH2 (an), γPh(X), 20b γPh ρSO2 17b, 20b γPh γPh, τNH2 (sulf) τNH2 (sulf), 15a, 17b, 20a τNH2 (sulf) tNH2 (an), 15a, 17b τNH2 (sulf) τNH2 (sulf) δCSN, 11b, 15a, 17b τNH2 (an), 10 τNH2 (an), 10 τPh, 4 τPh τPh
υ: stretching, δ: in-plane deformation, γ: out-of-plane deformation, br: broad, τ: torsional, t: twisting, v: very, m: medium, s: strong, w: weak, sulf: sulfonamide, an: aniline. Subscripts—a: asymmetric, s: symmetric.
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the range 355 ± 65 cm−1 [19]. Calculations give frequencies in the range 160–416 cm−1 for this mode as seen in Table 2. At 355, 364 and 388 cm−1 the torsion NH2 sulfonamide vibrations are not pure and contain contributions of phenyl ring modes also. In the Raman spectrum, the bands 298, 226, and 193 cm−1 are assigned as torsion of NH2 . The low frequency vibration at 40 and 92 cm−1 is assigned to the torsional mode of the phenyl ring. The SO2 antisymmetric stretching vibration appears in the region 1330 ± 30 cm−1 and the symmetric counterpart in the region 1160 ± 30 cm−1 both with high intensity [19,21]. The experimentally observed bands at 1313 cm−1 in the IR spectrum and 1315 cm−1 in the Raman spectrum are assigned to the υSO2 asymmetric modes and 1147 cm−1 in the IR spectrum and 1136 cm−1 in the Raman spectrum are assigned to the υSO2 symmetric modes. The calculations give 1346 and 1143 cm−1 as υSO2 asymmetric and υSO2 symmetric modes. Topacli and Topacli [16] assigned 1059 and 883 cm−1 theoretically and 1317 and 1144 cm−1 experimentally as asymmetric and symmetric modes of υSO2 . The SO2 scissors is assigned in the region 570 ± 60 cm−1 and the SO2 wagging vibration near 520 ± 40 cm−1 , both with medium intensity and clearly separated [19]. They are observed at 626 and 563 cm−1 in the IR spectrum of sulfanilamide. The C–S–N deformation is observed at 298 cm−1 in the Raman spectrum [19]. The CH stretching modes are expected in the region 3005–3115 cm−1 [19]. The calculated values are 3031, 3028, 3003 and 3002 cm−1 . These vibrations are observed at 3147, 3086 and 3062 cm−1 in the IR spectrum and at 3068 and 3050 cm−1 in the Raman spectrum with weak intensities. The bands observed at 1595, 1503, 1440 and 1188 cm−1 in the IR spectrum and 1594 and 1502 cm−1 in the Raman spectrum are assigned to ring stretching modes. This result is in agreement with Topacli et al. [16,24] for the strong IR bands at 1597, 1505 and 1440 cm−1 . The calculated values for this mode are 1583, 1541, 1501, 1427 and 1195 cm−1 . Topacli and Topacli [16] reported theoretical values to be at 1773, 1680, 1600, 1354 and 1266 cm−1 . These vibrations are expected in the range 1280–1620 cm−1 [19]. The out-of-plane CH deformation bands γCH are expected in the range 790–990 cm−1 [19]. As seen from Table 2, the ab initio calculations give frequencies at 1048, 1043, 891 and 865 cm−1 . The bands at 969, 837 cm−1 in the IR spectrum and 967, 842 cm−1 in the Raman spectrum are assigned to this mode. According to Topacli and Topacli [16] the experimental values are 1005, 967, 897 cm−1 and the calculated values are 1172, 1010, 973 cm−1 . The δ ring planar deformation modes are observed at 652 and 807 cm−1 theoretically. The bands at 807, 652, 573 and 571 cm−1 are not pure but contain contributions from Ph(X) substituent sensitive vibrations [19]. For 1–4 light heavy disubstituted benzenes δCH vibrations are seen in the range 1225–1315 cm−1 and 995–1190 cm−1 [19]. Topacli and Topacli [16] observed these vibrations at 1340, 1187 cm−1 in the IR spectrum and the theoretical values are 1500 and 1341 cm−1 . We have observed theoretical values at 1333, 1200, 1127, 1096 and 1002 cm−1 . The experimental values are observed at 1300, 1096 and 1003 cm−1 in the IR
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spectrum and at 1303, 1157, 1093 and 1002 cm−1 in the Raman spectrum. The υSN provides a weak to moderate band in the range 905 ± 70 cm−1 [19]. The S–N stretching vibration exhibits a strong band in the IR spectrum and a weak band in the Raman spectrum at 900 cm−1 [19]. Theoretically we have obtained a value 907 cm−1 corresponding to this band. In the spectra of N-substituted 2-thiophenesulfonamides, Arcoria et al. [25] assigned to υSN in the region 900 ± 65 cm−1 . The majority of the investigated secondary sulfonamides were found to give this stretching frequency at 910 ± 35 cm−1 [19]. Acknowledgements C. Yohannan Panicker would like to thank the University Grants Commission, India for awarding a Teacher Fellowship and Hema Tresa Varghese thanks University Grants Commission, India for a minor research grant. References [1] C. Munoz, in: J. Mardones (Ed.), Farmacologia, Intermedica, Buenos Aires, 1979 (Chapter 60). [2] F. Blasco, L. Perello, J. Latorre, J. Borras, S. Garcia-Granda, J. Inorg. Biochem. 61 (1996) 143. [3] S. Ferrer, J. Borras, E. Garcia-Espana, J. Inorg. Biochem. 39 (1990) 297. [4] C.T. Supuran, F. Mincoine, A. Scozzafava, F. Brigenti, G. Mincinone, M.A. Ilies, Eur. J. Med. Chem. 33 (1998) 247. [5] A. Garcia-Raso, J.J. Fiol, S. Rigo, A. Lopez-Lopez, E. Molins, E. Espinosa, E. Borras, G. Alzuet, J. Borras, A. Castineiras, Polyhedron 19 (2000) 991. [6] B.H. Oconnor, E.N. Maslen, Acta Crystallogr. 18 (1965) 363. [7] A.M. O’Connell, E.N. Maslen, Acta Crystallogr. 22 (1967) 134. [8] M. Alleaume, J. Decap, Acta Crystallogr. 19 (1965) 934. [9] M. Alleaume, J. Decap, Acta Crystallogr. 18 (1965) 731.
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