The mechanism of the alkylation of isoxazolidin-3-one

In solvents of different polarities, the lactam-lactim tautomeric equilibrium of isoxazoli-din-3-one is strongly displaced in the direction of the lactam. The lactim form cannot be detected. It has been concluded that there is no connection between the dual chemical behavior of isoxazolidin-3-one and its potassium salt in the alkylation reaction with the equilibrium isomerization of these compounds. It has been shown that the mechanism of alkylation is connected with the structure of the lactam anion. Evidence is given in favor of a mesomeric structure of the anion with the main charge on the nitrogen at which substitution chiefly takes place.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 898–901, July, 1973.     

Isotope anomalies of carbon, hydrogen and nitrogen in peat from the area of the tunguska cosmic body explosion (1908)

Abstract Peat profiles from the area of the Tunguska explosion epicentre indicate significant carbon and hydrogen isotopic effects which are clearly associated with the zone of the 1908 "catastrophe", and which cannot be attributed to any known terrestrial processes. We explain them with the presence of extraterrestrial matter similar to carbonaceous chondrites or, more probably, to cometary matter. Initial data on nitrogen content and its isotope composition are consistent with the assumption of acid rainfall following the passage and explosion of the Tunguska cosmic body, as is known to have occurred during the Cretaceous-Tertiary boundary.     

Prtolysis constants of pyridazin-6-one derivatives

The protolysis constants of pyridazin-6-one and some of its derivatives have been determined by the spectrophotometric method. The influence of substituents on the value of the protonation constants is discussed.Translated from Khimiya Geterots iklicheskikh Soedinenii, No. 7, pp. 993–995, July, 1973.     

Analogs of pyrimidine nucleosides

The reaction of alkoxy bromides with N₁-(-tetrahydrofuryl) derivatives of pyrimidine bases has given a series of 6-alkoxy-5-bromo-1-(-tetrahydrofuryl)-5, 6-dihydrouracils. The hydrogenation of the 1-(-tetrahydrofuryl) derivatives of uracil and of 5-fluorouracil has been studied. It has been shown that in both cases 1-(-tetrahydrofuryl)-5, 6-dihydrouracil is formed.     

Analogs of pyrimidine nucleosides

A number of N₁-(-butyrolactono) derivatives of 5-substituted uracils have been synthesized by condensing the sodium derivatives of the corresponding bases with -bromobutyrolactone or by the halogenation of N₁-(-butyrolactono)uracil.For part I, see [1].     

Zusammenhang zwischen L?slichkeit und Kapazit?tsfaktor bei der reverse-phase-bonded-phase-Chromatographie von Alkylbenzolen, Alkylbromiden und Alkyldisulfiden

Zusammenfassung Alkyldisulfide, Alkylbenzole und Alkylbromide wurden an einer chemisch gebundenen Kohlenwasserstoffphase (MicroPak-CH) mit Wasser-Methanol-Gemischen unterschiedlicher Zusammensetzung chromatographiert. In den entsprechenden Lösungsmittelgemischen wurden die SÄttigungslöslichkeiten der Probenkomponenten bestimmt. Man fand, da\ die SelektivitÄt innerhalb einer homologen Reihe durch die Löslichkeit der Glieder in der mobilen Phase bestimmt ist. Dabei lie\ sich der chromatographische KapazitÄtsfaktor mit guter Genauigkeit als k = b · (1/c_sat)^2/3 darstellen. log k und log c _sat hÄngen linear von der C-Zahl ab.

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Relation between solubility and capacity factor in the reverse-phase-bonded-phase chromatography of alkylbenzenes, alkylbromides and alkyldisulphides

Alkyldisulphides, alkylbenzenes and alkylbromides were chromatographed on a hydrocarbon type bonded stationary phase (MicroPak-CH) using water-methanol-mixtures of various composition as mobile phase. The solubility of the sample components was determined in the respective mobile phases. It was found that the selectivity within a homologous series is determined by the solubility in the mobile phase. The capacity factor can be expressed as k = b · (1/c_sat)^2/3. Log k and log c _sat depend linearly on the carbon number.

     

Chemistry of ethyleneimine

The mechanism of the reaction of N-aminoethyleneimine with some aliphatic aldehydes and with acrolein have been studied. It has been shown that the reaction takes place at the carbonyl bond C=O with the formation of hydrazones.For part II, see [1].     

Ways of formulating wind speed in heat convection significantly influencing pavement temperature prediction

This paper investigates the influences of wind speed and of heat-convection coefficient on the temperature prediction of a slab. Numerical calculation of a slab temperature found that wind speed varies the slab temperature in a degree of 2–10 °C. More varying degrees occur at midday and in sunny day but less, at midnight and in a cloud day. These degrees also depend on the used heat-convection coefficients, which have different values in different models. Special emphases are paid to unearth the correlation between different heat convection coefficients and find the best alternative in the slab-temperature prediction.     

DYNGA: a general purpose QM-MM-MD program. I. Application to water

We present a general purpose QM-MM-MD engine (DYNGA) designed to test alternative hybrid Hamiltonians geared towards the treatment of problems of interest in structural biology including the use of experimental data constraints. In this first presentation we use DYNGA to explore the behaviour of a traditional QM-MM approach in the treatment of the water—water interaction. We find the potential energy hypersurface for the water dimer computed with the HF 4–31G*/TIP3P hybrid Hamiltonian tends to be too flat. We also explore the effect of using traditional QM-MM techniques on proton wires and conclude there is a need for improvement, possibly addressed by using polarizable force fields.