Elementary reaction and anionic polymerization of isopropenly t‐butyl ketone

Abstract

Isopropenyl t‐butyl ketone (IPTBK) does not undergo radical homopolymerization and its anionic polymerization is a slow equilibrium process with a low ceiling temperature, which is due to its limited conjugation imposed by steric hindrance. Equimolar reactions of IPTBK with several anionic initiators were carried out, products isolated and identified by 1H‐and 13C‐NMR, and product distributions determined by GC. While n‐butyllithium and phenyllithium preferentially produce allyl alcohols, Grignard reagents predominantly undergo β‐addition to produce mono‐adducts, and a significant amount of dimers. t‐Butyllithium and t‐butylmagnesium chloride provide the cleanest β‐addition with minimal dimer formation and no carbonyl addition. However, Grignard reagent do not yield a polymer. The 1:1 reaction mixture of IPTBK with t‐butyllithium is very stable at 0°C, providing a methyl‐terminated mono‐adduct quantitatively when quenched with methyl iodide after 29 h. Addition of a second IPTBK to the mono‐adduct anion appears to be affected by the low ceiling temperature. Although t‐butyllithium can efficiently reduce as well as add to di‐t‐butyl ketone, such reactions are minor in the presence of IPTBK. Anionic polymerization of IPTBK with t‐butyllithium was carried out under several conditions. The 1:1 model reactions and the lack of acidic hydrogens in its structure suggest that anionic polymerization of IPTBK with t‐butyllithium may be “living.” The molecular weight distribution of the polymers ranged from 1.1 to 1.6 with the number‐average molecular weight varying from 2,800 to 233,500. Group transfer polymerization of IPTBK produced only a six‐membered lactone. Copyright © 1991 John Wiley & Sons, Inc.