Critical investigation of methods for kinetic analysis of thermoanalytical data

Journal of Thermal Analysis and Calorimetry -     

Reactions of Phosphorodiamidous Acid Esters with α-Halocarbonyl Compounds

Reactions of ethyl and tert-butyl phosphorodiamidites with chloroacetone, bromoacetone, and -chloroethyl acetate were studied. The reaction pathway is determined by the structure of the intermediate quasiphosphonium compound responsible for the formation of the Arbuzov product as well as for the occurrence of the amonalous reaction yielding vinyl phosphate.     

Interaction between 18-crown-6-tetracarboxylic acid and positional substituents of enantiomers and simultaneous separation of positional enantiomers of methyl-DL-tryptophans by capillary electrophoresis

18-Crown-6-tetracarboxylic acid (18C6H4) is a chiral selector with high selectivity for the enantioseparation of solutes bearing the primary amine function. This work presents the simultaneous separation of positional enantiomers of methyl-DL-tryptophans by using 18C6H4 as an additive to the background electrolyte. Separation conditions such as pH, the concentration of 18C6H4, and the applied voltages have critical inference on the simultaneous separation. The addition of cyclodextrins as anionic surfactants to the background electrolyte did not improve the separation. The selector-selectand interactions between 18C6H4 and the positional enantiomers have been investigated. It was observed that both the position and type of substituents contribute to the enantioselectivity. The migration order and resolution depended on the distance from the substituents to the asymmetric carbon of the enantiomers.     

Electrochemical reduction of phenylethynyl halides and related compounds

Reduction of phenylethynyl halides PhCCHal (Hal = I (1), Br (2), Cl (3)), diiodoacetylene (4), (phenylethynyl)triphenylphosphonium bromide (5), and related compounds in THF was studied by means of cyclic voltammetry using a glassy-carbon electrode. Compounds1–5 are reduced with cleavage of the C-Hal bond, and the reduction potentials increase in the order3 <2 <1 <4 <5.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2055–2057, October, 1995.     

Substituent effects on the nature of hydrogen bonding in organic hydroperoxides and the structure of triphenylmethyl hydroperoxide

It has been found that in the crystalline state in triphenylmethyl hydroperoxide the hydroperoxy group is involved in intermolecular hydrogen-bond formation of the type O-h..., with one C...C -bond in a benzene ring. Conformational analysis and comparison with the results of x-ray structural analysis leads us to conclude that there are very narrow limits on the possible conformations of the COOH group in tert-butyl, cumyl, 1,1-diphenylethyl, and triphenylmethyl hydroperoxides, independent of their aggregation state or the nature of the substituent attached to the COOH group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 68–73, January, 1990.