A theoretical study of an expanding monomer and an oxirane Part 1: Expanding monomer reactions

Spiroorthocarbonates have shown promise for use in polymerization reactions in which reduced shrinkage is desired. The purpose of this study was to use quantum mechanical methods to evaluate possible homopolymerization mechanisms to gain insight for likely reactions of 1,5,7,11-tetraoxaspiro[5.5]undecane (TOSU) using gas phase calculations. Protonation and subsequent ring opening was investigated and compared with ab initio calculations to determine the likelihood of reversibility. As experimental data collected from this group was inconsistent with the presumed propagation mechanism as well as previously studied mechanisms, an alternative mechanism was explored. AM1 results indicated a previously unreported mechanism for six-membered TOSU which forms 1,3-dioxan-2-one (cyclic carbonate) has calculated energetics which are competitive to other mechanisms and corroborate with experiment. DFT and RHF calculations further supported the competitiveness of this reaction. In addition, reactions with water were modeled to provide the likely mechanism for hydrolysis and subsequent termination of the cationic species.