B. Thimme Gowda

A study of substituent effect on the oxidative strengths of sodium salts of N-bromo-arylsulphonamides : Kinetics and mechanism of oxidation of D-fructose and D-glucose in alkaline medium

N-Bromo-arylsulphonamides of different oxidizing strengths are used for studying the kinetics of oxidation of D-fructose and D-glucose in aqueous alkaline medium. The results are analysed and compared with those from the sodium salts of N-bromo-benzenesulphonamide and N-bromo-4-methylbenzenesulphonamide. The reactions show zero-order kinetics in [oxidant], fractional order in [Fru/Glu] and nearly first order in [OH-]. Rates of oxidation of fructose are higher than those for glucose with the same oxidant. Similarly,Ea values for glucose oxidations are higher than those for fructose. The results are explained by a suitable mechanism and the related rate law is deduced. The effective oxidising species in the reactions of N-bromo-arylsulphonamides is Br+. The oxidative strengths of the latter therefore depend on the ease with which Br+ is released from them. The ease with which Br+ is released from N-bromo-arylsulphonamides depends on the electron density on the nitrogen atom of the sulphonamide group, which in turn depends on the nature of the substituent on the benzene ring. The validity of the Hammett equation has also been tested for oxidation of both fructose and glucose. Enthalpies and entropies of activations of the oxidations by all the N-bromo-arylsulphonamides correlate well. The effect of substitution onEa and logA of the oxidations is also considered

N-(2-Chlorobenzoyl)benzenesulfonamide

In the crystal structure of the title compound, C13H10ClNO3S, the conformation of the N—H bond in the C—SO2—NH—C(O) segment is anti to the C=O bond. The dihedral angle between the two benzene rings is 87.5 (1)°. The crystal structure features inversion-related dimers linked by pairs of N—H⋯O(S) hydrogen bonds.

Mechanistic investigations with positive halogens: kinetics of oxidation of thiosemicarbazide by chloramine-B, bromamine-B and dichloramine-B in acid medium

Abstract Kinetics of oxidation of thiosemicarbazide (TSC) by chloramine-B (CAB), and bromamine-B (BAB) in aqueous perchloric acid medium and by dichloramine-B (DCB) in 1:1 (v/v) water-methanol medium has been studied. The rate followed first order kinetics in [oxidant] and inverse fractional order in [H + ] with all the oxidants. But it was fractional order in [TSC] with CAB and independent of [TSC] with BAB and DCB. Addition of benzenesulphonamide, the reduced product of the oxidants had no effect on the rate with CAB and BAB but it slightly increased the rate with DCB. The rate decreased with increase in ionic strength of the medium in all cases. Decrease of dielectric constant of the reaction medium by adding methanol had no effect on the rate with CAB and BAB but increased the rate with DCB. The mechanisms proposed and the derived rate laws are in conformity with the observed results. The coefficients of the rate limiting steps have been calculated. Kinetics observed with HOCl and HOBr support the proposed mechanisms.

N-(4-Chlorobenzoyl)-2-methylbenzenesulfonamide

The asymmetric unit of the title compound, C14H12ClNO3S, contains two independent molecules. The dihedral angles between the two aromatic rings in each molecule are 81.0 (1) and 76.3 (1)°. In the crystal, molecules are linked by N—H⋯O hydrogen bonds.

2-Methyl-N-(3-methylbenzoyl)benzenesulfonamide

In the title compound, C15H15NO3S, the sulfonyl and amide-bound benzene rings are oriented at dihedral angles of 83.1 (1) and 22.5 (3)°, respectively, with the almost planar S—N—C=O segment (r.m.s. deviation = 0.003 Å). The dihedral angle between the two benzene rings is 74.8 (1)°. In the crystal structure, pairs of molecules are linked into centrosymmetric dimers by pairs of N—H⋯O hydrogen bonds.

N-Benzoyl-4-methylbenzenesulfonamide

In the title compound, C14H13NO3S, the N—H bond in is anti to the C=O bond. The dihedral angle between the two aromatic rings is 79.4 (1)°. In the crystal, molecules are linked by N—H⋯O hydrogen bonds, generating C(4) chains.

N-(2-Methylphenyl)benzenesulfonamide

In the title compound, C13H13NO2S, the conformation of the N—H bond is anti to the ortho-methyl group on the aniline ring, in contrast to the syn conformation observed with respect to the ortho-chloro group in N-(2-chlorophenyl)benzenesulfonamide. The dihedral angle between the two benzene rings is 61.5 (1)°. Molecules are linked into chains running along the a axis by N—H⋯O hydrogen bonds.

N-(2-Chlorophenyl)succinamic acid

The conformations of the N—H and C=O bonds in the amide segment of the structure of the title compound {systematic name: 3-[(2-chlorophenyl)aminocarbonyl]propionic acid}, C10H10ClNO3, are trans to each other, while the conformation of the amide H atom is syn to the ortho-chloro group in the benzene ring. Further, the conformations of the amide O atom and the carbonyl O atom of the ester segment are also trans to the H atoms attached to the adjacent C atoms. In the crystal structure, molecules are packed into infinite chains through intermolecular N—H⋯O and O—H⋯O hydrogen bonds.

2,4-Dichloro-N-(3,4-dichlorophenyl)benzenesulfonamide

In the crystal structure of the title compound, C12H7Cl4NO2S, the conformation of the N—H bond is syn to the meta-chloro residue in the aniline benzene ring. The two aromatic rings are tilted relative to each other by 68.9 (1)°. N—H⋯O hydrogen bonds connect the molecules into centrosymmetric dimers.

N-(2,6-Dimethylphenyl)benzamide

The conformation of the NH bond in the structure of the title compound (N34DMPBA), C15H15NO, is anti to the meta-methyl substituent in the aniline ring, similar to that observed with respect to the meta-chloro substituent in N-(3,4-dichlorophenyl)benzamide (N34DCPBA), but in contrast to the syn conformation observed with respect to the meta-methyl substituent in N-(3,4-dimethylphenyl)acetamide. The bond parameters in N34DMPBA are similar to those in N34DCPBA and other benzanilides. The molecules in N34DMPBA are packed into a column-like structure in the direction of the a axis through N—H⋯O hydrogen bonds.