Multiple bond migration with participation of a protophilic agent 2. Distinctions in mechanisms of multiple bond migration in propene and propyne molecules with participation of hydroxide ion

The pathways of migration of the multiple bond in propene and propyne molec ules involving the hydroxide ion were investigated by the ab initio (RHF/6- 31+G* and MP2/6-31+G*) methods. Stationary points corresponding to stable c omplexes between the molecules under study and the hydroxide ion and betwee n corresponding carbanions and water molecule were found on the potential. energy surfaces of the proton transfer reactions. In the presence of hydrox ide ion, migration of the multiple bond can occur by an "intramolecular" me chanism of the proton transfer involving the proton of hydroxide ion bound in the complex with propene or propyne molecule. For the propene system, su ch a mechanism seems to be quite realistic and more preferable energeticall y than a traditional two-stage mechanism with a passage of the proton into the medium. For the system with the triple bond, an equal expenditure of en ergy is required to follow any mechanism (without taking into account the e ffects of solvation and the interaction with a cation), whereas the formati on of the stable [H2C=C=CH . H2O](-) complex can prevent further transfomat ions.