Estudo ab-initio da a-alanina em meio aquoso

• Autor(a) principal: Sambrano,Júlio Ricardo
• Data de Publicação: 1999
• Outros Autores: Souza,Aguinaldo Robinson de, Queralt,Joaquim Josep, Andrés,Juan, Longo,Elson
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Química Nova (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40421999000400006
• topic: ab initio; <FONT FACE=Symbol>a</font>-alanine; solvent

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 <FONT FACE="Symbol">a</font>-alanine. The 6-31G* and 6-31++G** were taken from Gaussian94 library. We were concerned on the structure of three conformers of <FONT FACE="Symbol">a</font>-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.