Proton affinity and peculiarities of stabilization mechanism of carbanions

Regularities in MenX methyl derivative CH-acidity change depending on the X element position in the Periodic system are considered according to the data of measuring the kinetics of alkaline deuteroexchange in the liquid ammonium medium and values of proton affinity of carbanions in the gaseous phase. Relations, linking CH-acidity with certain literary characteristics of X-Me and C-H bond geometry and energetics, are analyzed. The analysis conducted as well as the results of non-empirical quantum-chemical calculations allow one to conclude that two competing factors, namely, delocalization at the expense of the upper occupied p-orbital overlapping on X-Me bond and exchange repulsion in which a notable past is played by the size of the central X atom, effect the CH-acidity change. Common features and differences in the effects determining changes in CH-acidity of MenX methyl derivatives and in XH-acidity of XHn hydrides with the simular structure, are found