N. K. Ray

Diamagnetic shieldings of atoms in molecules and their relation to electronegativity

It is shown that the diamagnetic shielding of an atom in a molecule, the quantity, σMd(α)=(e2/3mc2)〈1/rα〉, is exactly given by the formula where the Rαβe are the equilibrium internuclear distances in the molecule, μ is the negative of the electronegativity of the molecule, and We is the energy of the molecule as a function of the atomic numbers Zα and the net molecular charge Q. Combined with previously given empirical formulas for We (Ref. 1), this formula is shown to provide an easy method to estimate σMd values for atoms in neutral molecules.

MNDO study of reaction paths: Diboration of acetylene

The reaction of B2H4 with acetylene has been studied by the MNDO method. It is shown that the reaction is exothermic and proceeds in two steps. The first step is the formation of a three-center π-complex and this is the rate-determining step of the reaction. The second step is the rearrangement of the π-complex to the product and this step requires a very small amount of activation energy. The activation barrier for the diboration reaction is 12.8 kcal/mol.The proposed mechanism is significantly different from those proposed earlier and explains all experimental data relating to this reaction.

Average electron densities of first‐row atoms studies with a two‐parameter charge density function

The two‐parameters statistical model of Gazquez and Parr1 is used to estimate the ’’average electron density’’ of first row atoms and ions. (AIP).

Spin density distributions in some radical anions exhibiting restricted rotation about a carbon-carbon bond

In the radical anions of styrene, 4-vinyl pyridine and p-fluoro-styrene it has been found earlier by ESR experiments that the two ortho protons, as well as the two meta protons of the six-membered ring are not equivalent. We have made a systematic theoretical study of these systems by using the unrestricted Hartree-Fock method. Satisfactory agreement with the experimental results has been obtained without invoking the so called “α effect” or “β effect”.

The interaction of nitrogen and carbon monoxide with certain ions and neutral species

MNDO method is used to study the interaction of nitrogen and carbon monoxide molecules with a proton, hydrogen atom, hydride ion, hydrogen molecule ion and hydrogen molecule. Predicted geometries and heats of reaction of different complexes are presented. The wave functions are analyzed in terms of ground state charge distributions and overlap populations. Electronic effects accompanying complexation are also discussed.

MNDO study of reaction paths: Hydroboration of methyl cyanide

The hydroboration reaction of methyl cyanide has been investigated by the MNDO method. It has been shown that the reaction requires an activation energy of 25.3 kcal/mol and involves a four-center-like transition state in the rate-determining step. This reaction has been compared with the corresponding reaction of hydrogen cyanide, and the effect of methyl substitution on the reaction has been discussed. The charge-transfer effects accompanying the reaction have also been studied.

MNDO study of reaction paths: Hydroboration of carbonyl systems

The hydroboration reactions of acetaldehyde and acetone have been investigated by the MNDO method. The reactions have been shown to be twostep reactions involving an intermediate adduct. This adduct subsequently undergoes hydrogen rearrangement. The hydroboration reactions of acetaldehyde and acetone have been compared with the corresponding reaction of formaldehyde. The charge transfer effects accompanying these reactions have also been discussed.

Photocycloaddition of coumarin and carbostyril to olefins—An intermolecular orbital study

The intermolecular orbital theory of Salem has been used to study the photocycloaddition reactions of coumarin and carbostyril with 1-methoxy ethylene. Theoretical pathways have been drawn for the reactions and the magnitude of the ◊-electron stabilisation energy for the reactions has been calculated. All possible cycloaddition patterns have been examined and the relative importance of various interaction terms is discussed. Results of our calculations suggest that the bonds close in a concerted but asymmetric manner. The calculated regioselectivity correlates well with experimental data.

Floating spherical Gaussian orbital model study of average electric polarisabilities and magnetic susceptibilities: Some aliphatic hydrocarbons

Floating spherical Gaussian orbital model is used to discuss the average electric polarisabilities and magnetic susceptibilities of a series of hydrocarbons. It has been noticed that the core contributions are negligibly small and these quantities (average electric polarisabilities and magnetic susceptibilities) can be well estimated from contributions localised on bond Gaussians.