An NMR study of hydrogen exchange in p-hydroxybenzoic acid

The compound has been used over a temperature range in dimethylsulfoxide, with trichloroacetic acid and triethylamine as catalysts. The rate constant for uncatalyzed bimolecular exchange at 25 C is k_N=131 M^–1 sec^–1; the constant for acid-catalyzed exchange is k_A=0.9 · 10⁴ M^–1 sec^–1; and that for base-catalyzed exchange is k_B=0.5 · 10⁴ M^–1 sec^–1. The activation energy for uncatalyzed exchange is 5.75 kcal/mole. The exchange rates in dimethylformamide and acetone are higher, on account of differences in the hydrogen bond. The exchange rates of the isomers fall in the sequence ortho > para > meta, which is due to conjugation and intramolecular hydrogen bonding. The exchange mechanism is discussed. Simple relationships in dimensionless parameters are given for calculating the exchange rate from the shape of the NMR signal.     

Stereoisomers of 2-methyl-1-thiadecalin

A mixture of the geometrical isomers of 2-methyl-1-thiadecalin has been separated by a combination of adsorption column chromatography and preparative gas-liquid chromatography. The configuration of each isomer has been established by mass spectrometry and PMR spectrometry with the application of the Auwers-Skita rule.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 913–917, July, 1973.     

Predicting Microdistribution of Metal Electrodeposition Rate from Electrolytes with Positive and Negative Leveling Power

Russian Journal of Electrochemistry - The relationship between the leveling power of electrolytes, the primary current distribution, and the microdistribution of the metal deposition rate is...     

Synthesis and properties of halogenated derivatives of dibenzo-p-dioxine containing a trifluoromethyl group

Methods of preparation of a series of polyhalogenated dibenzo-p-dioxines containing the trifluoromethyl group in the 2 position are described. The physicochemical properties of these compounds are studied, electron impact mass spectra are discussed, and relative retention times are measured. In their gas-chromatographic and mass-spectral characteristics, some of the synthesized compounds are ,suited for use as internal standards in the quantitative determination of polychlorinated dibenzo-p-dioxines and dibenzofurans in the environment by means of the chromato-mass-spectrometric method.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals,Russian Academy of Sciences, Moscow 117071. Translated from Khim. Geterotsikl. Soedin., No. 7, pp. 902–907, July, 1994.