Abstract

COMPUTATIONAL STUDY ON THE PROTONATION OF PHENOXYMETHYLPENICILLIN-LACTIM BY AM1 METHOD

Manchi Shyamsunder*, Chithaluri Sudhakar and Bojja Rajeshwar Rao

ABSTRACT

The geometry, conformation and electronic structure of lactam-lactim tautomerism in phenoxymethylpenicillin have been optimized and calculated in the gas phase by semi-empirical molecular orbital AM1 method usually considering an isolated molecule surrounded by vacuum. In this connection, the mechanism of protonation in lactim tautomer of phenoxymethylpenicillin has been studied by comparison of the different positions of net charges at nitrogen atoms in the molecule. Further, the heats of formation (ΔHfo), dipole moment (μ), ionization potential (IP), full atomic charges and energies of frontier molecular orbitals (EHOMO and ELUMO) have been performed and discussed. The conformational analyses of mono- and di-protonated phenoxymethylpenicillin-lactim and their stable conformations have also been performed.

Keywords: AM1, lactam-lactim tautomerism, phenoxymethylpenicillin, induction effect, frontier molecular orbital.