%0 Journal Article
%T Spectroscopic Study and Semi-empirical Calculations of Tautomeric Forms of Schiff Bases Derived from 2-hydroxy- 1-naphthaldehyde and Substituted 2-aminothiophene
%A Abdullah M. Asiri
%A Khadija O. Badahdah
%A Salman A. Khan
%A Abdullah G. Al-Sehemi
%A Muhammed S. Al-Amoudi and Abeer A. Bukhari
%J Organic Chemistry Insights
%D 2012
%I 
%R 10.4137/OCI.S3687
%X New Schiff bases derivative were synthesized by reaction of 2-aminothiophene derivatives and 2-hydroxy-1-naphthaldehyde. The compounds exhibit intra-molecular hydrogen bonding and keto-enamine tautomerism were conformed by using IR and UV-Visible spectral data. The UV-Visible spectra of these compounds have been investigated in different solvents mainly acetonitrile and toulene. The compounds were in tautomeric equilibrium (enol-imine O每H＃N, keto-amine O＃H每N forms) in polar and nonpolar solvents. The keto-amine form was observed in both solutions of toluene and acetonitrile for some derivative. 1H-NMR and IR results showed that all Schiff bases studied favor the enol-imine form over the keto form in a weakly polar solvent such as deuterochloroform solution. The molecular structures of Schiff bases 4a每d enol and 5a每d keto semi-empirical AM1, PM3, MNDO and ab initio quantum mechanical (RHF/3每21G* and RHF/6每31G* basis set) was calculated in the gas phase. The relative energy of the keto-enol tautomeric equilibrium in the most methods of calculation in the gas phase is shifted toward the ketone form.
%U http://www.la-press.com/spectroscopic-study-and-semi-empirical-calculations-of-tautomeric-form-article-a2046