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Química Nova

Print version ISSN 0100-4042On-line version ISSN 1678-7064


SAMBRANO, Júlio Ricardo et al. Ab-initio study of a-alanine in aqueous medium. Quím. Nova [online]. 1999, vol.22, n.4, pp.501-505. ISSN 0100-4042.

Ab initio Hartree-Fock (HF), Density Functional (B3LYP) and electron correlation (MP2) methods have been used to caracterize the aqueous medium intramolecular hydrogen bond in a-alanine. The 6-31G* and 6-31++G** were taken from Gaussian94 library. We were concerned on the structure of three conformers of a-alanine, in their neutral form plus on the structure of the zwitterionic form (Z). The Z structure is a stationary point at the HF/6-31G* level but it is not when diffuse functions and electron correlation are included. This results shows that the Z form does not exist in the gas phase. The inclusion of solvent effects changed significantly the results obtained in gas phase, therefore this inclusion make the Z form a stationary point within all level of theory, and the relative energy depends dramatically on the level of calculation.

Keywords : ab initio; a-alanine; solvent.

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