Influence of Solvents on the Oxidation Kinetics of Aldehydic Group Compounds by Diethylammonium Chloro-chromate

The redox studies of some compounds containing aldehydic functional groups by diethyl ammonium chloro-chromate (DEACC) in dimethyl sulfoxide leading a product forming to acid of correspondimg order. Reactions are found to be in unit order with oxidant while a fractional order (less than unity) was found w.r.t. reductants. The redox reactions are influenced with acid, the acid dependence is governed by this equation: kobs = a + b[H+].. When isomeric form of aldehyde, that is Me-CDO is oxidised with the same oxidant it was observed a considerable K.I.E. (Deuterium effect; kH/kD = 05.69 at 298 K). The reaction of Acetaldehyde was done in various non aqueous medium, soluble or miscible in DMSO. The effect of solvent is studied fitting our data in the solvent model of Taft's and Swain's applied for this purpose.. Rate constants are correlating very well with already reported Taft’s values of *; further the reaction constants are negative in nature. Suitable mechanism involving are proposed with transfer of hydride ion..

Monobromoborane - Dimethyl Sulfide—a Highly Promising Reagent for the Regio- and Chemoselective Brominative Cleavage of Terminal Epoxides into Vicinal Bromohydrins

Monobromoborane–dimethyl sulfide (BH2Br–SMe2) is a highly regio- and chemoselective reagent useful for the brominative cleavage of the epoxy moiety into bromohydrins in the presence of alkenes, alkynes, ethers, acetals, ketals, and acetonides at 0°C, besides being an excellent hydroborating reagent. Several reactive functional groups, such as chloride, ketones, esters, nitriles, nitros, and thioethers, have been accommodated during such transformations. Although the reduction of acetophenone was completely suppressed at –25°C, 4-chlorobenzaldehyde still underwent 12–13% reduction of an aldehydic group.

Kinetics of reaction of 1,2-diaminobenzene with phenylglyoxal

The cyclization reaction kinetics of phenylglyoxal monohydrate with 1,2-diaminobenzene have been studied in formate, acetate, and phosphate buffers. At high pH values and low buffer concentrations the rate-limiting step consists in the protonation of the intermediate formed by addition of the first amino group to aldehydic group of phenylglyoxal. With increasing concentrations of formate and acetate buffers the rate-limiting step shifts to the formation of the intermediate. In phosphate buffers the catalysis by the basic buffer component makes itself felt, too. At higher concentrations of 1,2-diaminobenzene, the dehydration of phenylglyoxal monohydrate gradually becomes the rate-limiting step.

Vibrational analysis of (E,E)-2,4-hexadienal, (E,E,E)-2,4,6-octatrienal, and (E,E,E)-3-methyl-2,4,6-octatrienal

Attempted vibrational assignments of (E,E)-2,4-hexadienal, (E,E,E)-2,4,6-octatrienal, and (E,E,E)-3-methyl-2,4,6-octatrienal are given between 3100 and 50 cm−1. We particularly discuss spectroscopic effects of the aldehydic group presence, enlargement of the polyenal chain length, and methyl lateral substitution.

The binding of the coenzyme pyridoxal 5'-phosphate and analogues of the substrate-coenzyme complex to tyrosine decarboxylase

Phosphopyridoxyl derivatives, which are stable analogues of a substrate-coenzyme complex, are bound at the active site with great affinity. From a comparison of the interaction of a number of such compounds with the apoenzyme the delta G0 values for the binding of the substrate carboxy and phenyl groups and of the coenzyme aldehydic group were determined to be equal to (or more negative than) ‒3.8. ‒8.4 and ‒12.5kJ/mol (-0.9, ‒1.9 and ‒3kcal/mol) respectively; the delta G0 for the binding of the coenzyme phosphate group was shown to be more negative than ‒20.5kJ/mol (-4.9kcal/mol). Two features of the binding process of the coenzyme-substrate analogues to tyrosine decarboxylase have already been found in the case of tyrosine aminotransferase [Borri-Voltattorni, Orlacchio, Giartosio, Conti & Turano (1975) Eur. J. Biochem. 53, 151-160]: (1) in the binding of the substrate to the enzyme a significant fraction of the instrinsic delta G0 appears to be used for some associated endoergonic process; (2) the delta H0 and delta S0 of binding appear to be very sensitive indicators of the correct alignment of the substrate-coenzyme and analogues at the active site.