Study of [1,3] sigmatropic hydrogen migration in uracil, uridine and uridylic acid by AM1 method

Abstract

The geometry and electronic structures of uracil, uridine and uridylic acid involving [1,3] sigmatropic hydrogen migration in the formation of tautomers have been fully optimized and evaluated by semi-empirical molecular orbital AM1 method. 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>), full atomic charges, and energies of frontier molecular orbitals (E_HOMO and E_LUMO) have been calculated and discussed. The mechanistic investigation of [1,3] sigmatropic rearrangement in uracil affected in the conformational changes of uridine and uridylic acid has been studied by the comparison of net charges of atoms in different positions of the molecule. All tautomers exist with in the energy of 20.569 kcal/mol. Furthermore, dipole moment and atomic charges of all tautomers indicated that the dipole-dipole interactions play a vital role during the synthesis of proteins and enzymes.