Amperometric titrations with rotated platinum electrode: Determination of hydrazine by potassium bromate

The reaction between hydrazine and potassium bromate is studied amperometrically at rotating platinum electrode. The bromate titration is performed at an applied e.m.f. of zero (versus S.C.E.) and in the presence of bromide and 1–5N sulfuric acid or 0.5–4N hydrochloric acid. Quantities ranging from 30 μg to 3 mg of hydrazine can be estimated accurately by this method. Determination of phenylhydrazine, Semicarbazide and other oxidizable materials on similar lines is suggested.     

Ballistic phonon thermal transport in multiwalled carbon nanotubes

We report electrical transport experiments, using the phenomenon of electrical breakdown to perform thermometry, that probe the thermal properties of individual multiwalled carbon nanotubes. Our results show that nanotubes can readily conduct heat by ballistic phonon propagation. We determine the thermal conductance quantum, the ultimate limit to thermal conductance for a single phonon channel, and find good agreement with theoretical calculations. Moreover, our results suggest a breakdown mechanism of thermally activated C-C bond breaking coupled with the electrical stress of carrying approximately 10(12) A/m2. We also demonstrate a current-driven self-heating technique to improve the conductance of nanotube devices dramatically.     

Experimental evidence to support viscosity dependence of rates of Diels-Alder reactions in solvent media

This note is aimed at ascertaining whether rates of Diels-Alder reactions depend on the viscosity of solvent media in which the reactions are performed. On the basis of the data collected from the literature and in this laboratory, it is seen in general that the rates increase in the solvents with their viscosities ranging up to approximately 1.2 cP. In solvents possessing viscosities above 1.2 cP, a drop in the reaction rates is observed in all cases. The effect of temperature on the above phenomena is also examined.     

Flavor-changing radiativeB decays

We calculate the exclusive rate forB→K ^* (890)γ andB→K ^** (1400)γ arising from the quark subprocessb→sγ. These provide a good test of the standard model because they probe the flavor changing loop enhanced by QCD corrections. We have used relativised constituent quark model to evaluate the different form factors and estimate the recoil effects.     

Ru(III) catalysis in oxidation of n-propanol and n-butanol by acidic solutions of bromamine-ULE

Kinetics of Ru(III) catalysed oxidation of n-propanol and n-butanol by acidic solutions of bromamine-T have been investigated. The results show that oxidation of both alcohols follows first-order kinetics in bromamine-T, both alchols, hydrogen ion concentration and Ru(III). Decreasing effect of chloride ion]variation on reaction was observed. No effect of p-toluensulphonamide and ionic strength of the medium was observed. Activation parameters have been calculated and recorded. A suitable mechanism in conformity with the above observations has been proposed.     

Determination of enantiomeric excess of alpha-hydroxy-3-phenoxybenzeneacetonitrile and its n-butyl ester by chiral high-performance liquid chromatography

Determination of enantiomeric excess of alpha-hydroxy-3-phenoxybenzeneacetonitrile, an important intermediate in the production of several pyrethroid insecticides, is usually done after derivatization and gas chromatographic analysis on a beta-cyclodextrin-based column. In this communication we report a direct determination of enantiomeric excess of alpha-hydroxy-3-phenoxybenzeneacetonitrile and its n-butyl ester by chiral HPLC on Chiralcel OJ (Daicel, Japan) in a single run without derivatization.     

A short formal synthesis of squalamine from a microbial metabolite

A short formal synthesis of squalamine is described, utilizing the biotransformation product 2, which is available in one step from commercially available 3-keto-23,24-bisnorchol-4-en-22-ol (1). Regioselective C-22 oxidation and C-24 sulfation of the corresponding alcohols in the presence of a free C-7 alcohol make for an efficient preparation of squalamine intermediate 11.