Gerald Jay Gleicher

Calculations on the corannulene system

Abstract Self-Consistent Field MO calculations and strain energy calculations were applied to the recently prepared corrannulene system. The system is believed to exist in a non-planar configuration but should show appreciable aromatic character. Properties related to the π system have been determined.

Structural dependence of the rotational barrier in calicenes: A molecular orbital approach

Abstract Semi-empirical SCF MO calculations have been carried out for calicene and a variety of its derivatives. The pi binding energies of these species were obtained for both a planar structure and a structure where rotation about the intercyclic bond has occurred so that the two rings have assumed a perpendicular arrangement. While the absolute values of pi energy loss calculated by this approach are far too large, the relative values of the rotational barriers for various calicene derivatives follow expectations. It was shown that the incorporation of proper substituents into the molecule could lower the barrier to rotation either by inductive or conjugative effects. These effects would tend to stabilize structures with transfer of charge. Strain energy calculations, to assess the role of steric effects within the calicene system, are also discussed as are considerations of higher energy triplet states in the rotation phenomenon.

Radical chlorination of substituted t-butylbenzenes

Abstract A series of substituted t-butylbenzenes has been treated with sulfuryl chloride in the presence of benzoyl peroxide at 70°. For six of these compounds, the favored reaction was formation of a substituted neophy radical. While a correlation of data is obtained by application of the Hammett equation, the results may be better described by a field effect approach using a modified Kirkwood-Westheimer treatment.

Molecular orbital correlation of arylmethyl chloride atom abstraction by stannyl radicals

Abstract A series of monochloromethylated polycyclic benzenoid hydrocarbons have been treated with triphenyltin hydride and AIBN initiator at 70°C. Under these conditions the only observable reaction is reduction of the starting materials to methylarenes. A significant range of relative rates (factor of 40) has been found among the compounds studied. All relative rates yielded an excellent correlation when plotted against PPP-SCF calculated energy differences. The present works shows the ability of such calculations to treat processes involving nucleophilic radicals.

The reaction of iodomethylarenes with triphenyltin radical [1]. Use of molecular orbital modelling to evaluate the rate determining step

Abstract The relative reactivities of six polycyclic iodomethylarenes toward reduction by triphenyltin hydride in deuterobenzene at 70°C have been obtained. While a limited range of reactivities is observed, a trend does exist. Data are best correlated with calculated energy differences between transition states, based on adding an electron to the anti-bonding carbon—iodine orbitals, and parent arenes. These results agree with those obtained from substituent effect and isotope effect studies on other organic iodides which apparently undergo electron transfer with trialkyl or triaryltin radicals.

Additions of substituted phenylthiyl radicals to substituted α-methylstyrenes : Ground state and transition state electronic effects

Abstract The radical addition of substituted thiophenols to α-methylstyrene and substituted α-methylstyrenes has been investigated at 70°. Relative reactivities of pairs of thiophenols competing with individual alkenes can be utilized to obtain Hammett correlations. The interplay of substituent effects in alkene and thiyl radical leads to examples of non-linear rho values. Rationales for this behavior will be offered in terms of variable contributions from ground state and transition state electronic factors as well as in terms of possible mechanistic changes.

A correlation of the relative rates of heteroarylmethyl cation formation by SCF molecular orbital theory

Abstract Recent experimental findings have made it possible to extend molecular orbital correlations for the generation of arylmethyl systems to heteroaromatic species. In the present paper an SCF pi electron approach has been used to correlate the relative rates of pyrolysis of 1-pyridyl-, 1-quinolyl and 1-isoquinolylethyl acetates. Although far from good, it was found that calculated total energy differences yielded a correlation superior to that obtained from charge densities. The latter parameter, however, may have utility within the framework of a four parameter equation.

Steric and complexation factors in hydrogen abstraction from 1-phenylalkanes and α,ω-diphenylalkanes

Abstract As part of a systematic study of steric effects, 1-phenylalkanes and α,ω-diphenylalkanes were reacted at 70° with bromine atoms and trichloromethyl radicals. Exclusive benzylic bromination occurred in all cases. The 1-phenylalkanes reacted with both abstracting agents with rates which were largely independent of substrate. Intermolecular steric interactions must be negligible. In reaction with bromine atoms the α,ω-diphenylalkanes behaved in similar fashion. With trichloromethyl radicals, however, strong rate dependence with structure was observed. A maximum rate was found for 1,6-diphenylhexane. This is felt to be the result of intramolecular transfer of a complexed radical to the reaction site.

Hydrogen abstraction from substituted benzyl chlorides by the trichloromethyl radical

Abstract A series of ring substituted benzylchlorides have been reacted under photolytic conditions with bromotrichloromethane at 70°. Competitive kinetics show the bromination reaction to be substantially dependent upon ring substituents. A rho value of −1.02 (correlating with σ + ) was obtained with a correlation coefficient of −0.996. This is greater than has been observed for other α-substituted toluenes and is attributed to the slight radical destabilizing effect of the adjacent chlorine atom. A correlation between the ring substituent effects in various series of α-substituted toluenes and the electronic and steric requirements of the α-substituent has been developed.