排序方式: 共有15条查询结果,搜索用时 0 毫秒
11.
Dvorko G. F. Koshchii I. V. Ponomareva É. A. 《Theoretical and Experimental Chemistry》2003,39(2):99-103
In the series of substrates 1-bromo-1-methylcyclopentane, 1-bromo-1-methylcyclohexane, 1-methyl-1-chlorocyclopentane, 1-methyl-1-chlorocyclohexane, the heterolysis rate in acetone at 25 °C is reduced by four orders of magnitude; v = k[RX], E1 mechanism. The decrease in reaction rate as we go from a cyclopentyl compound to a cyclohexyl compound is due to the decrease in entropy of activation as a result of rapid solvation of the transition state as the conformational barrier is overcome. 相似文献
12.
Dirichlet boundary value problems are studied for thin elastic plates on an elastic foundation within Kirchhoff's classical model. The aim is to construct dual problems that make it possible to obtain bilateral error estimates for approximate solutions. In the absence of an elastic foundation, the dual functionals are maximized on function sets whose elements satisfy certain differential restrictions. The theory is illustrated by means of a numerical example. 相似文献
13.
Parameters were refined for synthesis of glycerol 1-monomethyl ether by methylation of glycerol with dimethyl sulfate in the presence of alkali; a gas-liquid chromatographic procedure was proposed for identification of structural isomers of mono-O-methylglycerol. 相似文献
14.
Dvorko G. F. Koshchii I. V. Prokopets A. M. Ponomareva E. A. 《Russian Journal of General Chemistry》2002,72(11):1797-1804
Heterolysis of 1-methyl-1-chlorocyclopentane in protic and aprotic solvents occurs by the E1 mechanism. The reaction rate in aprotic solvents or in a set of protic and aprotic solvents is satisfactorily described by the parameters of the polarity and electrophilicity or ionizing power of the solvents. In protic solvents, the reaction rate grows with increasing polarity or ionizing power of the solvent and decreases with increasing nucleophilicity. 相似文献
15.
Heterolysis of 1-bromo-1-methylcyclohexane in cyclohexane (E1 reaction) involves solvation of the transition state (ΔS≡ = ?81 J mol?1K?1), while heterolysis of 1-chloro-1-methylcyclohexane is characterized by desolvation of the transition state (ΔS≡ = 92 J mol?1K?1). The probability for the formation of transition state (interaction between cationoid intermediate and solvent cavity) increases in the first case due to enhanced stability of the solvated intermediate, and in the second, due to reduction in its size. The bromide/chloride heterolysis rate ratio decreases as the ionizing power of aprotic solvent decreases and that of protic solvent increases. 相似文献