Susan Erfani - Department of Chemistry, The University of Sistan and Baluchestan,
Sayyed Mostafa Habibi-Khorassani - Department of Chemistry, The University of Sistan and Baluchestan,

Quantum mechanical calculations were undertaken for determination of the stability of the two isomers Z and E of compounds (2E)- methyl 3-(1-(3-tert-butyl-2-hydroxy-5-methylphenyl)isoquinolin-2(1H)-yl) acrylate .and (2E)-ethyl 3-(1-(3-tert-butyl-2-hydroxy- 5-methylphenyl)isoquinolin-2(1H)-yl) acrylate . Theresults showed that isomer E is more stable than Z . Results (theoretical calculations) were consistent with the experimental data arised from NMR spectroscopy.For assignment of the two Z and E isomers in compounds (2E)- methyl 3-(1-(3-tert-butyl-2- hydroxy-5-methylphenyl)isoquinolin-2(1H)-yl)acrylate .and (2E)-ethyl 3-(1-(3-tert-butyl-2-hydroxy- 5-methylphenyl)isoquinolin-2(1H)-yl) acrylate , first their structures, were optimized at the HF/6-31G(d,p) level of theory by Gaussian 98 program. The relative stabilization energies for both isomers have beencalculated at the HF/6-31G (d,p) and B3LYP/6- 311++G (d,p) levels. Further calculations in the gas phase are also non-polar and polar solvents. Thenumbers of critical points and intramolecular hydrogen bonds have been recognized as well as the charge of atoms that were constructed on the twoisomers. In addition, Jx-y , the values of proton and carbon coupling constant, and also chemical shifts (δHiso,δCiso) have been calculated at the mentionedlevel using the SPINSPIN keyword.

Quantum mechanical, stability, isomer Z , isomer E Isoquinolines, hydrogen bond, AIM, NMR, NPA