| Investigations into several, often polycyclic, intermediates are described. The nature of these intermediates, whether electronically aromatic, delocalized, or localized; trishomocyclopropenium or bishomo square pyramidal; radical, cation, or singlet or triplet carbene; reflects the diversity of organic chemical reactions.;Solvolyses of exo- and endo-4-deltacyclyl brosylates and exo-5-isodeltacyclyl brosylate had been observed to give products suggesting multiple intermediates along the reaction pathway. The cations of these molecules were examined computationally, and it was revealed that non-classical deltacyclyl cation is about 13.3 kcal/mol more stable than classical deltacyclyl cation and 9.8 kcal/mol more stable than isodeltacyclyl cation at the BPW91/6-311 + g(3df,2p)//BPW91/6-31g(d) level.;Structural, energetic, and magnetic criteria calculations, based on B3LYP/6-31g(d) optimized geometries, were conducted on a series of tricyclopropenium and bishomo square pyramidal cation and carbene intermediates. These calculations revealed that some singlet carbene intermediates can mirror the homoaromatic qualities of their cation cousins. Specifically, the criteria examined revealed that trishomocyclopropenium singlet carbenes centered at the 8-position of tricyclo[3.2.1.02,4]octane and the 9-position of pentacyclo[4.3.0.0 2,4.03,8.05,7]nonane are clearly homoaromatic in nature. However, the trishomocyclopropenium singlet carbene centered at the 6-position of tricyclo[3.1.1.02,4]heptane is not homoaromatic, while the bishomo square pyramidal carbene also centered at the 6-position of tricyclo[3.1.1.02,4]heptane is homoaromatic.;Analysis of the photochlorination products from a series of fused cyclopropyl-norbornane ring systems revealed that the ability of the bridgehead carbon to adopt a preferred bisected geometry does not affect the rate at which a hydrogen is abstracted from that position. However, the orientation of the cyclopropane ring relative to the bridgehead, and the relative stability of the formed radicals does correlate with the rate at which a hydrogen is abstracted from the bridgehead. In addition, a hydrogen atom at the anti-C8 position of endo-tricyclo[3.2.1.02,4]octane was revealed to be abstracted about 15.5 times more often than a hydrogen atom at the C7-position of norbonane.;Formation of a radical cation-radical anion exciplex intermediate in the photolysis of N,N-dimethylaniline in the presence of ortho-dichlorobenzene was confirmed by Stern-Volmer analysis. However, this exciplex cannot be formed by similar photolyses of phenothiazine, 1,4-dimethoxynaphthalene, or aminopyrazine. |
