In previous papers, 13 the synthesis of 1, 1-diphenyl-3, 3-dibromoprop-l-ene (I) from 1, 1- diphenylprop-2-yn-l-ol and phosphorus tribromide in acetic acid has been reported. During the course of the studies of the reactions of the gem-dibromide (I), some novel reactions were found. The present paper deals with these reactions and will discuss the reaction mechanism.