Ab initio study of vibrational spectra of alanine in gas phase

R. Kumar, A.K. Sharma, S.D.S. Chauhan, D. Kulshreshtha, R. Gupta, P.K.S. Chauhanı and O.P. Singh²

Department of Physics, ıDepartment of Chemistry, Paliwal (P.G.) College, Shikohabad - 205 135 (India). ²Department of Physics, Udai Pratap Autonomous College Varanasi - 221 002 (India).

Received on August 08, 2009 and accepted on October 15, 2009

ABSTRACT

The vibrational frequencies for the fundamental modes and the energies of low lying states of alanine in neutral and its zwitterionic form in gas phase have been calculated at RMP2 ab-initio level. The results so obtained have been compared with earlier theoretical calculations and experimental observations of IR and RAMAN spectrum. In the present study, it has been observed that our results are more nearer to the experimental observations than earlier Semi-empirical AM1 and ab-initio Restricted Hartree Fock and Density Functional Methods. It is also observed that unlike RHF/6-31G method of computation, Z-alanine could not maintain its zwitterion form with RMP2/6-31G method

Keywords : IR; Raman; Vibrational Frequencies; RMP2; L, D, Z-Alanine.