Mahboob Mohammad

Kinetics and electrochemical studies on superoxide

Rate constants for the reaction of superoxide O-2 with various substrates were obtained through stationary electrode polarography theory and technique. In solvent acetonitrile, the substrate and the rate constants of the reaction O-2 + AH-k2→Product, are, AH = isopropanol (k2 < 0.01 M-1 s-1); ethanol (k2 = 1.42 × 102 M-1 s-1); methanol (k2 = 1.1 × 107 M-1 s-1), H2O (k2 = 1.0 × 105 M-1 s-1). In MeCN, O-2 was found to be rather unreactive towards glucose and acetone but it reacts with fructose and sucrose catalytically. However, in DMF2, O-2reacts with glucose and fructose with k2 order of 105 M-1 s-1. The mechanism of the reaction of O-2 with the substrates (AH) is proposed as O-3 + AH k2O, AHk2k-1 k′ [O2H + AH]-, k-2→O2H + A- with k1 = 109 M-1 s-1 and k-1 = 108 -109 s-1. With these values of k-1 and k1, k′ k2(obs). The reversible E1/2 for O2 + e O-2 in various solvents: MeCN, acetone, isopropanol, methanol, H2O were obtained either directly from the reversible voltammogram or from experimental voltammograms and the rate constants obtained (as above) using stationary electrode polargraphy theory; E1/2 being -0.82 (MeCN),-0.85 (acetone),-0.72 (isopropanol);-0.66 (MeOH),-0.56 (H2O) vs SCE.

Protonation of anion radicals and dianions of some dinitro aromatics

A simple electrochemical method developed to study reactions of reactive intermediates (neutralfree readical, cation-, anion- radicals etc.) was employed to study the protonation reaction of anion radicals and dianions of some dinitroaromatics. Rate constants thus obtained and the mechanism of protonation reaction invesitgated, are reported. It is suggested that the reactions do not involve a direct electron transfer. The possible role of various ion-pairs was investigated. Positions of nucleophilic attack were investigated through M.O. calculations.

Are pyridinyl radicals really the reactive intermediates

Abstract The behaviour of the reduction products of the herbicide paraquat (1,1′-dimethyl-4,4′-bipyridilium dichloride) and 1-ethyl-4-carbomethoxy pyridinium salt, vis a vis proton donors and oxygen were investigated. The rate constants for the protonation reaction of these reduction products, with various protonating agents, were evaluated. Also, the effect of solvent and electrode surface on the reaction of these reduction products with oxygen were investigated. It was found that the nature of the electrode surface had a profound effect on the reaction with oxygen, which could have a bearing on the herbicidal activity of paraquat. It was also found that the higher reduction products are 10 4 –10 5 times more reactive than the initial reduction products 1-ethyl-4-carbomethoxypyridinyl radical and 1,1′-dimethyl-4,4′-bypiridilium cation radical. Hence, the possible role of more reactive higher reduction products in the herbicidal properties of paraquat is pointed out.

Superconductivity in Y-Ba-Na-Cu-O

The Y-Ba-Ca-Cu-O superconductor (Ca0.2Y0.3Ba0.5CuO3−z) was prepared under different heat treatments and sintering conditions. Electrical resistance measurements from ambient temperature to 77 K show that four of the five samples were single-phase superconductors withTc in the range 82 to 85 K. The X-ray diffraction measurements revealed an orthorhombic perovskite type structure for all samples.

Acetyl Salicylic Acid (Aspirin) and Antioxidative Agents in Joshanda - a Herbal (Medicinal) Tea

Joshanda**, a herbal medicine taken as tea, claimed to be a remedy for some ailments, was analyzed for acetyl salicylic acid and antioxidative property. HPLC analysis of Joshanda showed 18.3 ppm acetyl salicylic acid in it. Cyclic voltammetric analysis of Joshanda tea for its antioxidative property was done by using simple and novel electrochemical device recently developed and reported. It established the presence of some antioxidative agent(s) (antioxidants). The presence of these chemicals may render this herbal medicine (tea) beneficial for general health. **The name of the manufacturer of Joshanda Sample analyzed is classified.