Dipole Moments and Configurations of Triaryl Acrilonitriles

The electric dipole moments of trans-1,2 diaryl acrilonitrile 1 and of a series of triaryl acrilonitriles 2-14 were measured in benzene solution at 25 °C. A mesomeric moment of 0.4 D was found to act between the phenyl-and the nitrile groups through the vinylic bond in triaryl acrilonitrile 2. For this molecule the direction of action of the total molecular moment was calculated and used to evaluate theoretical moments for the possible E and Z configurations of some unsymmetrical derivative compounds of the series. The configuration was settled for each com-pound on the basis of comparison between experimental and calculated dipole moment values.

The electronic structure of cyclopentadienylindium

CNDO calculations have been carried out for the molecule InC5H5 of C5υ symmetry. Overlap populations were calculated and compared with those for related species. The bonding between In and the organic moiety can be described as essentially a covalent interaction involving mainly indium 5s and 5p orbitals with ring pπ orbitals. A lone pair on indium is a dominant feature of the structure, and is largely responsible for a (calculated) dipole moment of 4.75 D. The calculated orbital energies are compared with experimental photoelectron spectra.

Methyl Substitution Effects on the Proton Chemical Shifts in Benzene

Methyl substitution effects on aromatic and methyl proton chemical shifts in several mono-, di-, and trimethyl benzenes are studied. A new method for obtaining the changes in the ring proton chemical shifts from those of methyl proton shifts at the corresponding positions is used. The extra π-electron densities in toluene are calculated using the already known relation between the π-electron densities and the proton shifts in aromatic systems. An inverse relationship is obtained between the ionization potentials and the total methyl effects on the chemical shifts in this series of compounds as one would expect. Dipole moment of toluene is calculated, and a reasonably good agreement is found between the experimentally observed and the calculated dipole moment.