K. Jyothi

Infrared and NMR Spectra of Arylsulphonamides, 4-X-C6H4SO2NH2 and i-X, j-YC6H3SO2NH2 (X=H; CH3; C2H5; F; Cl; Br; I or NO2 and i-X, j-Y=2,3-(CH3)2; 2,4-(CH3)2; 2,5- (CH3)2; 2-CH3, 4-Cl; 2-CH3, 5-Cl; 3-CH3, 4-Cl; 2,4-Cl2 or 3,4-Cl2)

Several arylsulphonamides of the configuration, 4-X-C6H4SO2NH2 (where X= H; CH3; C2H5; F; Cl; Br; I or NO2) and i-X, j-YC6H3SO2NH2 (where i-X, j-Y=2,3-(CH3)2; 2,4-(CH3)2; 2,5-(CH3)2; 2-CH3,4-Cl; 2-CH3,5-Cl; 3-CH3,4-Cl; 2,4-Cl2 or 3,4-Cl2) were prepared, and their infrared spectra were measured in the solid state. The NMR spectra were recorded in solution. N-H asymmetric and symmetric stretching vibrations absorb in the ranges, 3390 - 3323 cm-1 and 3279 - 3229 cm-1, respectively. Asymmetric and symmetric SO2 stretching vibrations appear as strong absorption lines in the ranges, 1344 - 1317 cm-1 and 1187 - 1147 cm-1, respectively. Sulphonamides exhibit S-N stretching vibrational absorptions in the range, 924 - 906 cm-1. The effect of substitution in the phenyl ring in terms of electron withdrawing and electron donating groups could not be generalised, as the effect is non-systematic. The chemical shift is highly dependent on the electron density around the nucleus or associated with the atom to which it is bonded. Hence empirical correlations relating the chemical shifts to the structures have been discussed. The chemical shifts of aromatic protons and carbons in all the arylsulphonamides have been calculated by adding substituent contributions to the shift of benzene, the principle of substituent addition. Considering the approximation made, the agreement between the calculated and experimental chemical shift values is reasonably good. Generally, electron-withdrawing groups shows high chemical shifts compared to electron-donating groups.

Crystal Structure Studies on p-Substitutedbenzenesulphonamides 4-X-C6H4SO2NH2 (X = CH3, NH2 F, Cl or Br)

Effect of ring substitution on the crystal structures of p-substitutedbenzenesulphonamides, p-XC6H4SO2NH2 (X = F, Cl, Br, CH3 or NH2) has been studied by determining the crystal structures of 4-chlorobenzenesulphonamide (4-ClC6H4SO2NH2) and 4-bromobenzenesulphonamide (4-BrC6H4SO2NH2) and analyzing the results along with the structures of 4-methylbenzenesulphonamide (4-CH3C6H4SO2NH2), 4-fluorobenzene-sulphonamide (4-FC6H4SO2NH2) and 4-aminobenzenesulphonamide (4-NH2C6H4SO2NH2). The crystal type, space group, formula units and lattice constants in Å of new structures are: (4-ClC6H4SO2NH2); monoclinic, P21/n, Z = 4, a = 6.6276(10), b = 16.219(3), c = 7.5716(10), β = 93.387(14)°; (4-BrC6H4SO2NH2): monoclinic, P 21/n, Z = 4, a = 6.5660(10), b = 16.4630(10), c = 7.6900(10), β = 92.760(10)°. Orientation of the amine group with respect to the phenyl ring is given by the torsion angles C(2)-C(1)-S-N: 70.9° and C(6)-C(1)-S-N: −108.5°. Similarly, the orientation of S, O(1) and O(2) with respect to the ring are given by torsion angles. The comparison of bond lengths and bond angles of 4-fluoro-, 4-chloro-, 4-bromo-, 4-methyl- and 4-amino-benzenesulphonamides reveal that the S-N and C-S bond lengths decrease with the introduction of electron-withdrawing substituents such as F, Cl or Br, while these groups do not have significant effects on the S-O distances. The effect on ring C-C distances was not uniform. Substitution of F, Cl or Br decreases the O-S-N bond angle, but increases the O-S-N, N-S-C(1) and C(3)-C(4)-C(5) bond angles.

35Cl NQR and structural studies on substituted amides, XyC6H5-yNHCOR (X = H or Cl; y = 0, 1 or 2 and R = C(CH3)3, CHClCH3, C6H5 or 2-ClC6H4)

35Cl NQR frequencies of some N-(substitutedphenyl)-amides represented by the general formula, XyC6H5−yNHCOR (where X = H or Cl; y = 0, 1 or 2 and R = H, CH3, CH2CH3, CH(CH3)2, C(CH3)3, CH2Cl, CHCl2 or CCl3) have been measured and compared with those of other compounds in the family to analyse the effect of substitution in the side chain on the frequencies. Comparison of 35Cl NQR frequencies of all the N-(2-chlorophenyl)- and N-(2,6-dichlorophenyl)-amides reveals that the presence of alkyl groups in the side chain lowers the frequency, while that of aryl or chlorosubstituted alkyl groups enhance the frequencies to some extent, when compared to the frequencies of either N-(2-chlorophenyl)-acetamide or N-(2,6-dichlorophenyl)-acetamide. In addition, the crystal structures of N-(phenyl)-2-chloro-2-methylacetamide (C6H5NHCOCHClCH3) and N-(phenyl)-2- chloro-benzamide (C6H5NHCO-(2-ClC6H4)) have been determined and the data analysed along with the crystal structures of related compounds. The data (lattice constants in Å) of the new structures are: C6H5NHCO- CHClCH3: monoclinic, P21/c, Z = 4, a = 10.879(2), b = 9.561(2), c = 10.067(2), β = 116.080(10)°; C6H5NHCO-(2-ClC6H4): tetragonal, P4(3), Z = 4, a = 8.795(4), b = 8.795(4), c = 15.115(6), β = 90.0°. It is evident from a comparison, that the side chain substitution influences the C(S)-C(O) bond length, while the effect on the other bond lengths is not significant except for benzanilide. Similarly, only the side chain angles are affected to some extent. The variations do not show definite trends, probably due to the differences in the crystallisations.

Infrared, 1H and 13C NMR Spectral Studies on Di- and Tri-substituted N-Aryl Amides, 2,6-X2C6H3NHCOCH3 – IXi and 2,4,6-X3C6H2NHCOCH3 – IXi (X = Cl or CH3 and I = 0, 1, 2 or 3)

Several di- and tri-substituted amides of the general formula, 2,6-X2C6H3NHCOCH3−iXi and 2,4,6-X3C6H2NHCOCH3−iXi (X = Cl or CH3 and i = 0, 1, 2, or 3) are prepared, characterised, and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution are studied. The C=O stretching vibrations of N-(2,6-dichlorophenyl)- and N-(2,6-dimethylphenyl)-amides appear as strong absorptions in the ranges 1707 - 1658 cm−1 and 1700 - 1647 cm−1, respectively, while the N-H stretching vibrations of N-(2,6-dichlorophenyl)- and N-(2,6-dimethylphenyl)-amides appear as strong vibrations in the ranges 3271 - 3209 cm−1 and 3285 - 3214 cm−1, respectively. The N-H stretching vibrations of N-(2,4,6-trichlorophenyl)- and N-(2,4,6-trimethylphenyl)- amides also appear as strong absorptions in the ranges 3370 - 3212 and 3283 - 3225 cm−1, respectively, while those of the C=O vibrations appear in the ranges 1688 - 1617 and 1704 - 1647 cm−1. The analysis of the C=O and N-H absorption frequencies of all amides of the general formula XiC6H5−iNHCOCH3−iXi (where X = Cl or CH3, and i = 0, 1, 2 or 3) indicates that their variations do not show regular trends with substitution either in the phenyl ring or in the side chain. The chemical shifts of both the aromatic protons and the aromatic carbons of all the amides are calculated in two ways, either by adding the incremental shifts due to -COCH3−iXi groups and the substituents in the benzene ring to the chemical shifts of the corresponding aromatic protons or carbons of the parent aniline, or by adding the incremental shifts due to -NHCOCH3−iXi groups and the substituents in the benzene ring to the chemical shift of the benzene proton or carbon. The calculated chemical shifts of the aromatic protons and carbons of all the substituted amides by both methods lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating that the principle of additivity of the substituent effects is valid in these compounds.

Synthetic, infrared, 1H and 13C NMR spectral studies on potassium salts of N-chloroarylsulphonamides

Several N-chloroarylsulphonamides of the configuration, 4-X-C6H4SO2(K)NCl・xH2O (where X = H, CH3, C2H5, F, Cl or Br) and i-X, j-YC6H3SO2(K)NCl・xH2O (where i-X, j-Y = 2,3-(CH3)2; 2,4- (CH3)2; 2,5-(CH3)2; 2-CH3,4-Cl; 2-CH3,5-Cl; 3-CH3,4-Cl; 2,4-Cl2 or 3,4-Cl2) are prepared, characterised, and their infrared spectra in the solid state and NMR spectra in solution are measured and correlated. Comparison of the infrared spectra of the potassium salts of N-chloro-arylsulphonamides with the corresponding arylsulphonamides shows that the strong absorptions in the range 947 - 933 cm−1 are due to N-Cl stretching vibrations. The effect of ring substitution on the N-Cl frequencies is non-uniform. The frequencies in the ranges 1404 - 1370 cm−1 and 1149 - 1125 cm−1 are respectively assigned to S=O asymmetric and symmetric vibrations. The effect of substitution in the phenyl ring in terms of electron withdrawing and electron donating groups is non-systematic. Empirical correlations relating the chemical shifts to the structures are considered. The chemical shifts of aromatic protons and carbons in all the N-chloroarylsulphonamides have been calculated by adding substituent contributions to the shift of benzene, as per the principle of substituent addition. Considering the approximation made, the agreement between the calculated and experimental chemical shifts is reasonably good.

Kinetics and Mechanism of Oxidation of Dimethyl Sulphoxide by Mono- and Di-Substituted N,N-Dichlorobenzenesulphonamides in Aqueous Acetic Acid

In an effort to introduce N,N-dichloroarylsulphonamides of different oxidising strengths, four mono- and five di-substituted N,N-dichlorobenzenesulphonamides are prepared, characterised and employed as oxidants for studying the kinetics of oxidation of dimethyl sulphoxide (DMSO) in 50% aqueous acetic acid. The reactions show first order kinetics in [oxidant], fractional to first order in [DMSO] and nearly zero order in [H+]. Increase in ionic strength of the medium slightly increases the rates, while decrease in dielectric constant of the medium decreases the rates. The results along with those of the oxidation of DMSO by N,N-dichlorobenzenesulphonamide and N,N-dichloro-4- methylbenzenesulphonamide have been analysed. Effective oxidising species of the oxidants employed in the present oxidations is Cl+ in different forms, released from the oxidants. Therefore the introduction of different substituent groups into the benzene ring of the oxidant is expected to affect the ability of the reagent to release Cl+ and hence its capacity to oxidise the substrate. Significant changes in the kinetic and thermodynamic data are observed in the present investigations with change of substituent in the benzene ring. The electron releasing groups such as CH3 inhibit the ease with which Cl+ is released from the oxidant, while electron-withdrawing groups such as Cl enhance this ability. The Hammett equation, log kobs = −3.19 + 1.05 σ , is found to be valid for oxidations by all the p-substituted N,N-dichlorobenzenesulphonamides. The substituent effect on the energy of activation, Ea and log A for the oxidations is also analysed. The enthalpies and free energies of activation correlate with an isokinetic temperature of 320 K.

Infrared, 1H and 13C NMR Spectra of N,N-Dichloroarylsulphonamides, 4-X-C6H4SO2NCl2 (X = H, CH3, C2H5, F, Cl or Br) and i-X, j-YC6H3SO2NCl2 (i-X, j-Y = 2,3-(CH3)2, 2,4-(CH3)2, 2,5-(CH3)2, 2-CH3, 4-Cl, 2-CH3, 5-Cl, 3-CH3, 4-Cl, 2,4-Cl2 or 3,4-Cl2)

Several mono- and di-substituted N,N-dichloroarylsulphonamides of the configuration, 4-XC6H4SO2NCl2 (where X = H, CH3, C2H5, F, Cl or Br) and i-X, j-YC6H3SO2NCl2 (where i- X, j-Y = 2,3-(CH3)2, 2,4-(CH3)2, 2,5-(CH3)2, 2-CH3,4-Cl, 2-CH3,5-Cl, 3-CH3,4-Cl, 2,4-Cl2 or 3,4-Cl2), respectively, were prepared, characterised and their infrared spectra in the solid state and NMR spectra in solution state were measured and correlated. Comparison of the infrared spectra of the N,N-dichloroarylsulphonamides with the corresponding arylsulphonamides and Nchloroarylsulphonamides revealed that the infrared absorption bands in the ranges, 790 - 735 cm−1 and 595 - 546 cm−1 are due to N-Cl asymmetric and symmetric stretching vibrations, respectively, and that the effect of ring substitution on the N-Cl frequencies is not consistent. The frequencies in the ranges 1384 - 1333 cm−1 and 1181 - 1143 cm−1 are, respectively, assigned to S=O asymmetric and symmetric modes of vibration. The effect of substitution in the phenyl ring in terms of electron withdrawing and electron donating groups is non-systematic. Since the chemical shift depends on the electron density around the nucleus, empirical correlations relating the chemical shifts to the structures have been considered. The chemical shifts of aromatic protons and carbons in all the N,Ndichloroarylsulphonamides have been calculated by adding substituent contributions to the shift of benzene. Considering the approximation made, the agreement between the calculated and experimental chemical shifts is good.