Abstract

AM1 STUDY ON THE ELECTRONIC STRUCTURE AND CONFORMATIONS OF LACTAM-LACTIM TAUTOMERISM IN PHENETHICILLIN

Banda Upender Reddy, Bojja Rajeshwar Rao and Battu Satyanarayana*

Abstract

The geometry, conformation and electronic structure of lactam-lactim tautomerism in phenethicillin 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 phenethicillin has been studied by comparison of the different positions of net charges at nitrogen atoms in the molecule. Further, the heats of formation (ΔHf o), 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 lactim tautomers and their stable conformations have also been performed.

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