- EFFECT OF VICINAL SUBSTITUENTS ON THE REACTIVITY IN BIMOLECULAR NUCLEOPHILIC SUBSTITUTION AT A SATURATED CARBON ATOM. TWO TYPES OF SUBSTITUENTS II. KINETICS OF THE REACTION OF THIOUREA WITH β-SUBSTITUTED BROMOETHANES IN ETHANOL
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The kinetics of the reaction of thiourea with β-substituted bromoethanes in ethanol were studied by radiochromatography.The rate constants and activation parameters of the reactions were determined.It was shown that an isokinetic relationship is observed for the two types of substituents.The mechanisms of the effect of the vicinal substituents on the reactivity are discussed.
- Ryazantsev, G. B.,Shaposhnikov, A. V.,Fedoseev, V. M.
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p. 1777 - 1782
(2007/10/02)
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- EFFECT OF VICINAL SUBSTITUENTS ON REACTIVITY IN BIMOLECULAR NUCLEOPHILIC SUBSTITUTION AT A SATURATED CARBON ATOM. TWO TYPES OF SUBSTITUENT I. KINETICS OF THE REACTIONS OF THIOUREA WITH β-SUBSTITUTED BROMOETHANES IN DIMETHYLFORMAMIDE
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The kinetics of the reaction of thiourea with β-substituted bromoethanes in DMFA were studied by radiochromatography.It was shown that there is no isokinetic relationship or Taft equation for all the substituents but that there are isokinetic relationships for two separate reaction series, one of which is described satisfactorily by a Taft equation taking account of the inductive and steric effects of the substituents.On the basis of the obtained data it is supposed that there are two types of vicinal substituents, which affect the reactivity of the bromine at the saturated carbon atom by different mechanisms.For the first type of substituent (H, F, Br, CH3, C6H5) the main factors determining the reactivity are the inductive and steric effects of the substituents.Substituents of the second type (COOH, COOC2H5, CN, NH3Br, SC(NH2)2Br) include charged or highly polar substituents, and this makes it possible to expect a field effect, leading to additional stabilization of the transition state.
- Ryazantsev, G. B.,Lys, Ya. I.,Fedoseev, V. M.
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p. 776 - 779
(2007/10/02)
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