ANALYSIS OF THE ELECTRON-DENSITY REDISTRIBUTION IN THE COURSE OF NUCLEOPHILIC-ADDITION REACTIONS OF H- AND F- TO ACETYLENE AND METHYLACETYLENE MOLECULES ACCORDING TO AB-INITIO CALCULATIONS

Energy characteristics and peculiarities of variation of structural pa rameters along the minimum energy pathways (MEP) calculated earlier of six reactions of nucleophilic addition of H- and F- to acetylene and methylacetylene have been analyzed. The electronic mechanism of the re actions, the character of the electron density redistribution, and its relation with the changes in structural parameters have been discusse d. It has been found for all six reactions that the structural reorgan ization of an alkyne + Nu system is completed before the barriers. How ever, the increase in the alkyne multiple bond length and changes in e lectronic characteristics for the reactions with F- (endothermic react ions) take place before the barrier (late transition state) and for th e reaction with H- (exothermic reactions), after the barrier (early tr ansition state).