Question

4. Isobutylene undergoes cationic polymerization in the presence of strong Lewis acids like AICI, but it is not polymerized by free radicals or anionic initiators. Acrylonitrile, on the other hand, is polymerized commercially by free radical means also by anionic initiators like potassium amide but does not respond to cationic initiators. Explain this difference in behavior of isobutylene and acrylonitrile in terms of monomer structure and what intermediates would be formed under each polymerization condition CN Acrylonitrile Isobutylene

Answer 1

Cationic reaction polymerization ń kind of repitative Alkylation Int + - - lewis Acid Bfz, ABY 3, Ticla & Int-cth-(-(the - Int -cth - Co RR ALBY, Ticly are act as initiator free radical polymerization ;) Chain initiating step. 1 R-O-OR RO' 2) R-O + CH = cth R-O-CH-Cth radical Initator radical 11) chain propogation step R-o-Cth-CH + CH = CH R -o-cth- CH - Cty-eth Jetc cth I ta C HẨt - - H (thy HA Ke -> H C C A + H 1 / Isobutylene н -cth H Cty H 30 carbocation h the I th - - çe ť oth the Anionic polymerization i poyeble only when monomer contain a CN highly election withdrawing group adjusent to vinyl group. Acrylonitrile. H Hinn "CN H CN -CN An H inuator C . x-<-<- I-u-I I-ur Iu- I - ń CN 4 CN