Chemical properties of some 1,1,2-trifluoropentadienes

A study has been made of some chemical properties of three 1,1,2-trifluoropentadienes. The first two were conjugated dienes, one containing an electron releasing group and the other an electron withdrawing group. They were made by adding CF 2 B r CFClB r to propene and CF 2 ClCFCl I to 3,3,3-trifluoropropene, respectively, and dehydrohalogenation and dehalogenation to produce CF 2 CFCHCHCH 3 (I) and CF 2 CFCHCHCF 3 (II). The third diene, an unconjugated perfluoro compound, was made from CF 2 ClCFClCF 2 CF 2 CO 2 Na. Diene I had a marked ability to react with itself even at 0° to form the perfluorocyclobutyl derivative. When I was heated with CF 2 CFCl or CF 2 CCl 2 only the dimer of I was formed. Diene II formed the cyclobutyl dimer at 100° and, when heated with I, formed all three of the possible perfluorocyclobutyl products. The unconjugated perfluoropentadiene formed no cyclic products either alone or with CF 2 CFCl. Both I and II reacted with phenylmagnesium bromide to give the dienes in which a fluorine atom had been replaced by a phenyl group. Ethanol in the presence of base reacted with I to give a mixture of 1,2− and 1,4− addition products in a ratio of 4:1. Pentafluorodiene II gave only the ether resulting from 1,4− addition of alcohol. Radical reactions with bromotrichloromethane were also carried out. Mechanisms to account for the products will be presented.