Dehydrohalogenation with hydrogen transfer

Isotope effects and element effects associated with hydron-transfer steps during methoxide promoted dehydrohalogenation reactions of jo-CF3C6H4C HClCH2X (X=Br, Cl, or F) have also been discussed, with regard to distinction between E2 and multi-step pathways. The Arrhenius behaviour of hydrogen isotope effects was used to calculate the amounts of internal hydrogen return associated with the two-step mechanism. 

Dehydrohalogenation. Aryl vinyl ethers are prepared conveniently by dehy-drohalogenation of aryl 2-haloethyl ethers with aqueous sodium hydroxide with tetra-n-butylammonium hydrogen sulfate as phase-transfer catalyst (equation I). 

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. 

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