Effect of Cationic Micellar Aggregates on the Kinetics of Dextrose Oxidation by N-Bromophthalimide

The effect of cationic micelles of Cetyltrimethyl ammonium bromide (CTAB) on the kinetics of oxidation of dextrose by N-Bromophthalimide were studied at 40°C. The reaction follows fractional-order and first order kinetics, with respect to [dextrose] and [NBP], respectively. CTAB strongly catalyze the reaction, and typical k_obs and [CTAB] profile was observed, that is, with a progressive increase in [CTAB], the reaction rate increased, reaches a maximum value then decreased. Results are treated quantitatively in terms of Berezin's Model, which is applicable to bimolecular micellar catalyzed reaction. There is a negative effect of mercuric acetate and phthalimide. The influence of salts on the reaction rates has also been seen. The activation parameters as well as other parameters were calculated and suitable mechanism consistent with the experimental findings has been proposed.     

Antibacterial,Antioxidant and Binding Studies of Some Novel Diaryl Sulphide Derivatives

Abstract

A series of novel acyclic and cyclic diaryl sulphides was synthesized from 2,2′-dithiobenzoic acid. The various diaryl sulphides were characterized by use of spectral (IR, ¹H and ¹³C NMR, ESI/MS) and elemental analyses. The antimicrobial activities of the compounds were evaluated in terms of their minimum inhibition concentration (MIC) against a panel of clinical isolates bacteria and were found to possess only moderate antimicrobial activities. N,N′-Bis(2-hydroxyphenyl)-2,2′-thiodibenzamide (13), exhibiting a hydroxy group at the phenyl ring, was the most active antimicrobial agent within the series, with MIC values of 0.05 mg mL^–1 and 10 mg mL^–1 against Staphylococcus aureus and Bacillus cereus, respectively. The antioxidant efficiency of the diaryl sulphides was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity with 13 being the most active compound. The interaction of 2,2′-thiodibenzanilide, N,N′-bis(2-methylphenyl)-2,2′-thiodibenzamide, and N,N′-bis(2-hydroxyphenyl)-2,2′-thiobenzamide with guanine, glutamic acid, and urea were studied quantitatively with binding constants ranging from 1 × 10³ M^?1 to 2.7 × 10⁴ M^?1.     

Three anilides of 2,2′‐thiodibenzoic acid

The structures of N,N′‐bis(2‐methylphenyl)‐2,2′‐thiodibenzamide, C₂₈H₂₄N₂O₂S, (Ia), N,N′‐bis(2‐ethylphenyl)‐2,2′‐thiodibenzamide, C₃₀H₂₈N₂O₂S, (Ib), and N,N′‐bis(2‐bromophenyl)‐2,2′‐thiodibenzamide, C₂₆H₁₈Br₂N₂O₂S, (Ic), are compared with each other. For the 19 atoms of the consistent thiodibenzamide core, the r.m.s. deviations of the molecules in pairs are 0.29, 0.90 and 0.80 Å for (Ia)/(Ib), (Ia)/(Ic) and (Ib)/(Ic), respectively. The conformations of the central parts of molecules (Ia) and (Ib) are similar due to an intramolecular N—H...O hydrogen‐bonding interaction. The molecules of (Ia) are further linked into infinite chains along the c axis by intermolecular N—H...O interactions, whereas the molecules of (Ib) are linked into chains along b by an intermolecular N—H...π contact. The conformation of (Ic) is quite different from those of (Ia) and (Ib), since there is no intramolecular N—H...O hydrogen bond, but instead there is a possible intramolecular N—H...Br hydrogen bond. The molecules are linked into chains along c by intermolecular N—H...O hydrogen bonds.     

硫酸存在时N-溴代苯二甲酰亚胺对甘露糖的胶束催化氧化

The kinetics of micellar-catalyzed oxidation of mannose by N-bromophthalimide was studied in the presence of sulfuric acid at 313 K. The orders of reaction with respect to [mannose], [oxidant], and [H+] were found to be fractional, first, and negative fractional order, respectively. Anionic micelles of sodiumdodecyl sulfate showed a partial inhibitory effect, while cationic micelles of cetyltrimethylammonium bromide increased the reaction rate with the same kinetic behavior. The reaction was catalyzed by cationic micelles, because of favorable electrostatic/thermodynamic/hydrophobic/hydrogen bonding between reactants and cationic micelles. Their catalytic roles are best explained by Berezin’s model. A variation of [phthalimide] showed that the rate of reaction decreased with increasing [phthalimide]. It was observed that, an increase of [mercuric acetate] had no effect on reaction velocity. The influence of salts on the reaction rate was also studied. The rate constant (kW ), binding constants (KS+KO), and corresponding activation parameters (Ea, ⊿H#, ⊿S#, and ⊿G#) were determined. A detailed mechanism with associated reaction kinetics is presented and discussed.