Journal of Physical and Theoretical Chemistry
Volume:2 Issue: 1, Spring 2005

The results of MNDO, AM1 and PM3 semi-empirical calculations and HF/6-31G*, MP/6-31G*, MP2/6-311+G**, and B3LYP/6-311G** and QCISD/6-31G* ab initio methods for angle strain and conjugation effects in twist-boat, boat, and half-chair geometries of (Z,Z,Z)-cycloocta-1,3,5-triene indicate that all methods, except PM3, predict wrong ordering of the conformations.

Structural and magnetic properties of purine and pyrimidine nucleotides (CMP, UMP, dTMP, AMP, GMP, IMP) were studied at different levels of ab initio molecular orbital theory. These calculations were performed at the hartree-fock level and density functional B3LYP methods. Geometries were fully optimized by following Cs symmetry restrictions. The standard 6-31G** basis set which includes polarization and diffuse functions, was used for all the calculations.  The gauge-invariant atomic atomic orbital (GIAO) method and the continuous-set-of-gauge-transformation (CSGT) procedure was employed to calculate atomic shielding tensors of the nucleotides using density theory at the B3LYP/6-31g** and HF/6-31g** level. The calculated chemical shifts were used to aid in assigning in the NMR spectra.

We have evaluated the NMR shielding tensors for A:T,G:C,A:U in Watson-crick, and U-quartet. We have computed NMR shielding tensors at B31YP level by using 6-31G(d) basis set. We have compute anisotropy and asymmetry in A:T,G:C,A:U and U-quartet. The NMR shielding tensors were calculated using the GIAO method.
The natural bonding orbital analysis (NBO) were performed. NBO calculation have been done at B31LYP level. We have evaluated lowest occupancy orbitals, highest energy, donor and acceptor atoms, core and valence orbitals, total Lewis, natural population in atoms in NBO calculation.

The dependence on ionic strength of protonation of glycine and its complexation with dioxouranium (VI) is reported in sodium perchlorate and sodium chloride solutions as background salts. The measurements have been performed at 25±0.1°C and various ionic strengths in the range 0.1 to 1.0 mol , using a combination of potentiometric and spectrophotometric techniques. The overall analysis  of the present  and the previous data dealing with the determination of stability constants at different ionic strengths allowed us to obtain a general equation, by which a formation constant determined at a fixed ionic strengths can be calculated, with a good approximation, at another ionic strength, if 0.1  ionic strength  1.0 mol  sodium perchlorate or sodium chloride.

Using the evaporating method, the solubility of potassium Nitrate was determined in various mixtures containing Water and Ethanol at 25°C. The results show that the solubility of KNo3 decreases with increasing the mass percent of Ethanol in the mixtures. This trend is along with decreasing the dielectric constant of Water+Ethanol mixtures. Moreover, it can be concluded that the totqal solubility of KNO3 may be regarded as the sum of two contributions; one referring to the free ions in the solution and the other to K+NO3-ion-pairs which are formed in the saturated solution. Estimating the formation constant, KAm for the reaction K+(soln) + NO3-(soln) AK+NO3-
(ion-pair) , upon Bjerrum or fuoss models, then it is quite easy to evaluate the contributions of free ions and K+NO3-(ion-pair) to the total solubility.

An efficient and environmentally friendly procedure for one-pot synthesis of 13-acetyl-9-methyl-11-ox-8-oxa-10,12-diazatricyclo [7.3.1. ] trideca-2,4,6-triene from salicylaldehyde, acetylaceton and urea via Biginelli condensation and intramolecular Michael-addition by using magnesium bromide as an expensive and easily available catalyst under solvent-free condition is desired. The structural elucidation of the product is also described by -and -NMR spectra and the detailed fragmentation routs of EI-TOFMS

The structural properties of a new cyclic phosphor amide have been investigated in three methods and four basis sets and results have been compared with experimental data by spss. The best level for this type compound is HF/6-31++G** and with considering to this result, at this level, hyper chem input as initial geometry have been evaluated.