AM1 study on the conformations of zwitterions of 6-aminopenicillanic acid (6-APA)

Abstract

The geometry and electronic structure of zwitterions of 6-aminopenicillanic acid (6-APA) have been optimized and calculated by semi-empirical molecular orbital AM1 method. The mechanism of formation of zwitterions of 6-APA has been studied by comparison of the different positions of net charges on nitrogen atoms in the molecule. In this connection, the heats of formation (<img src='/image/spc_char/delta.gif' border=0>H_f˚), dipole moments (<img src='/image/spc_char/micro.gif' border=0>), ionization potentials (IP), full atomic charges, and energies of frontier molecular orbital (E_HOMO and E_LUMO) have been performed and discussed. The effect of conformational changes and electronic properties of stable conformations have been determined.