MNDO and ab initio Calculations of Methyl 2-Lithioisobutyrate and Its Solvates and Aggregates

Abstract

Ab initio and semiempirical (MNDO) molecular orbital calculations are reported of the energies, charge distributions, and geometries of methyl 2-lithioisobutyrate (LIMIB) used as a model of the propagation centre in the anionic polymerization of (meth)acrylates. Two stable forms energetically not very differing were found, one being near to the enolate, the other nearer to the keto form, both at the MNDO and 6-31G** levels. Stabilization energies and geometries of the dimer, trimer, and tetramer aggregates of LIMIB and of its solvates with dimethyl ether molecules were calculated at the MNDO level. These results agree with our earlier experimental findings obtained with the tetrahydrofuran solutions of LIMIB.