Proton methoxide promoted

Part V is devoted to the study of H transfers in organic and organometallic reactions and systems. In Ch. 18 Koch describes kinetic studies of proton abstraction from CH groups by methoxide anion, of the reverse proton transfer from methanol to hydrogen bonded carbanion intermediates, and of proton transfer associated with methoxide promoted dehydrohalogenation reactions. Substitutent effects, kinetic isotope effects and ah initio calculations are treated. Of great importance is the extent of charge delocalization in the carbanions formed which determine the kinetic and thermodynamic acidities. 

This chapter is divided into three sections Proton transfer from carbon acids to methoxide ion proton ttransfer from methanol to carbanion intermediates proton transfer associated with methoxide promoted dehydrohalogenation reactions. 

Proton Transfer Associated with Methoxide Promoted Dehydrohalogenation Reactions... 

Proton Tranter Associated with Methoxide Promoted Dehydrohaiogenation Reactions I 577... 

Such nucleophilic displacements are likely to be addition-elimination reactions, whether or not radical anions are also interposed as intermediates. The addition of methoxide ion to 2-nitrofuran in methanol or dimethyl sulfoxide affords a deep red salt of the anion 69 PMR shows the 5-proton has the greatest upfield shift, the 3- and 4-protons remaining vinylic in type.18 7 The similar additions in the thiophene series are less complete, presumably because oxygen is relatively electronegative and the furan aromaticity relatively low. Additional electronegative substituents increase the rate of addition and a second nitro group makes it necessary to use stopped flow techniques of rate measurement.141 In contrast, one acyl group (benzoyl or carboxy) does not stabilize an addition product and seldom promotes nucleophilic substitution by weaker nucleophiles such as ammonia. Whereas... 

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