J.B. Moffat

The isomers of diazomethane

Abstract Total electronic energies and energies of isomerization have been calculated with STO-3G and 6–31G basis sets for the energy-optimized geometries of the seven isomers of diazomethane. Cyanamide and isodiazirine are the most and least stable, respectively, of the isomers. With the STO-3G basis, diazirine is predicted to be more stable than diazomethane, but the reverse is found with the 6–31G basis set. Differences between the results found with the two basis sets and experimental data are attributed to the favouring of cyclic structures by the STO-3G basis, and to differences in correlation energy among the various isomers.

Methyl group rotation barrier in γ-picoline

Abstract Ab initio calculations on γ-picoline predict a small methyl rotational barrier of approximately 14 calories mole −1 in good agreement with the experimental value of 13.7 calories mole −1 [1].

A group contribution method applied to electronic correlation energies of molecules

Abstract A scheme for assigning molecular correlation energies to bonds within the molecule is proposed and applied to a variety of molecules for which nonempirical electronic energies and heats of formation are available. The bond correlation energies are employed to predict the molecular correlation energies of some molecules and good agreement was found between the predicted and “experimental” values.

n-Propyl cyanide and isocyantde: rotational and structural isomerization

Abstract Ab initio calculations with an STO-3G basis and geometry optimization have been performed on n-propyl cyanide and isocyanide in four rotational conformations, trans, cis, and gauche, with, in the latter case, two different dihedral angles, 90° and 120° from the trans position, being employed. The trans and gauche 120° isomers are predicted to be the most stable for both the cyanide and isocyanide, and the cyanide—isocyanide energy difference is calculated to be approximately 22 kcal mole−1 for each rotational isomer. The results of a population analysis are employed to discuss the electronic structures of the cyanide, isocyanide, and the isomerization process.

The electronic structure and nonplanarity of cyanamide: II. Cndo/2 calculations

Abstract CNDO/2 calculations on various nuclear configurations provide evidence for the nonplanar geometry of cyanamide. The out-of-plane angle is calculated to be 56° and a barrier to inversion of 0.0120 hartree is found.

Some ab initio calculations on boron nitride

Abstract Ab initio calculations on the 1 Σ + state of boron nitride (BN) nave been performed using basis sets of 22, 32, and 48 Gaussian functions. The equilibrium internuclear distance and total electronic energy obtained with the largest basis set were 2.35 bohr and −78.8580 hartree, respectively.

Comparison of the structures of cyanamide, difluorocyanamide and dimethylcyanamide

Abstract Ab initio calculations using a minimal basis set were employed to obtain geometry-optimized nuclear configurations for cyanamide, difluorocyanamide and dimethylcyanamide. The geometry-optimized structures in all cases predict a pyramidal amide form with the pyramidal nature increasing from difluorocyanamide to dimethylcyanamide, in agreement with previous experimental results. In addition, with all three molecules, the calculations predict a bent NCN bond, in agreement with experimental data for difluorocyanamide. However, no previously reported experimental work for either cyanamide or dimethylcyanamide has provided evidence for such an observation. Population analyses are examined to provide information on the factors contributing to the structures of these molecules.

The dimers of cyanamide

Abstract Ab initio calculations have been performed on various dimeric forms of cyanamide. The “nondissociative” dimerization of cyanamide leads to cyclic molecules all of which are unstable with respect to cyanamide. However, the molecules produced by “dissociative” dimerization are stable relative to cyanamide. Dicyandiamide is found to be the most stable of nine dimeric configurations.

Dicyanoketene and its isomers

Abstract Ab initio STO-3G calculations have been performed on dicyanoketene and its isomeric forms. Optimized nuclear configurations and relative stabilities are examined and compared with those of ketene and oxirene. Heats of formation and bond substitution energies are estimated.

A comparative theoretical study, from ab initio calculations, of the 1Σ+ states of CN+ and CN−

Abstract LCAO-MO-SCF calculations with a basis set of nine s and five p Gaussian functions have been performed on the 1 Σ + states of CN + and CN − from which total electronic energies and one-electron energies are calculated for 15 and 10 internuclear separations, respectively. Equilibrium internuclear separations of 2.25 and 2.214 bohr corresponding to total electronic energies of −91.5678 and −92.2465 hartree were found for CN + and CN − , respectively. The ionization potential of the CN radial is estimated to be 14.10 eV and the force constant of CN + to be 3.9 × 10 16 hartree cm −2 compared with the experimental values 14.03 eV and 3.6 × 10 16 hartree cm −2 respectively, obtained by Lutz. The present results on CN + appear to represent the only calculations so far performed, while the CN − values appear to be the best so far available as a function of internuclear distance.