The internal strain in cyclic amides are explained as a factor of resonance that are effected on the bond length C-N and are a major factor of rates of hydrolysis. The cyclic amides in this study are optimized by Gaussian program and the bond length of C-N in the rings are studied by HF/6-31G*.

Scale factors for obtaining fundamental vibrational frequencies, low-frequency vibrational frequencies, zero-point vibrational energies (ZPVEs), and thermal contributions to enthalpy and entropy have been derived through a least-squares approach from harmonic frequencies determined at more than 100 levels of theory. Wave function procedures (HF, MP2, QCISD, QCISD(T), CCSD, and CCSD(T)) and a la...

In this paper,the molecular geometry for three tautomers of uracil and four tautomers of cytosine has been analyzed. vibrational IR spectra of the tautomers were   investigated at HF and B3LYP level using the AB initio 6-31G* and LANL2DZ basis sets from the program package Gaussian 98 (A.7 Public Domain version). The physico-chemical and biochemical properties of uracil and cytosine are one of...

A neural-network-based approach was applied to correct the systematic deviations of the calculated heats of formation for 180 organic molecules and led to greatly improved calculation results compared to the first-principles methods [J. Chem. Phys. 119 (2003) 11501]. In this work, this neural network approach has been improved by using new descriptors obtained from natural bond orbital analysis...

The potential energy surface of gaseous glycine determined years ago in the ab initio B3LYP/6-311++G** calculations is composed of thirteen stable conformers. We performed the ab initiomolecular orbital calculations as the starting point to carry out a force field and normal coordinatecalculation on the most stable conformer of non-zwitterionic glycine [conformer (I)]. Thecalculations were carr...

for better understanding of conformational stability of the dipeptide model hco—gly—l—leu—nh2,ab initio and dft computations at hf/6-31g(4 6-311++g(d,p) and b3lyp/6-31g(d) levels oftheory were carried out. geometry optimization of the dipeptide within the leucine (leu) side chainangles (x2 ,x2) resulted in three stable conformations as followings: anti-anti, the most stable one,(xi = 180°, x2 =...

in this study the hardness swct was calculated with b3lyp,hf method and 3-21g,6-31g,6-311g basis set .then it was investigated with the best method(b3lyp) and basis set(6-31g) to study the adsorption effects co2 on the hardness of swcnt with gap homo-lumo in two shape: horizontal, vertical and top-center-bridge and we also provide the effects of co2 adsorption on the electronic properties(dos) ...

The (13)C and (1)H isotropic chemical shift values computed at HF, BLYP, B3LYP, and MPW1PW91/6-311+G(2d,p) levels of theory, for the BLYP and B3LYP/6-31G(d,p) optimized geometries of adamantane, 2-adamantanone, and 2,4-methano-2,4-dehydroadamantane ([3.1.1] propellane) are reported and compared with the experimental data. Except for the "inverted" carbon atoms and some of their nearest neighbor...

The internal strain in cyclic amides are explained as a factor of resonance that are effected on the bond length C-N  and are a major factor of rates of hydrolysis. The cyclic amides in this study are optimized by Gaussian program and the bond length of C-N in the rings are studied by HF/6-31G*.