An exploratory ab initio study on the conformations of ethylguanidine in its neutral [CH3-CH2-NH-C(=NH)NH2] and protonated [CH3-CH2-NH-C(NH2)+] forms

M. L.MAK; S. SALPIETRO; ENRIZ R D; I G CSIZAMDIA

CANADIAN JOURNAL OF CHEMISTRY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Lugar: Otawa; Año: 2000 vol. 78 p. 626 - 641

0008-4042

To explore the conformation intricacies of the guanidine group in the arginine side chain, ab initio computationshave been carried out with ethylguanidine and the ethyl guanidinium ion. HF computations have been performedusing 3-21G and 6-31G basis sets and DFT calculations were carried out at the B3LYP/6-31G(d) leve! of theory. Theethyl guanidinium ion has a single isomer due to its interna! symmetry, although this structure has at least three conformations.However, severa! structures were found and optimized for ethylguanidine, involving the endo- andexo- orientation of the lone NH and torsional angle Xó, as well as the torsional modes associated with X4 and Xs·Torsional angle :X:s gives rise to s-cis and s-trans structures.