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The α,β-unsaturated nitrile, bicyclo[2.2.1]heptene-2-carbonitrile, I, was synthesized from norcamphor. Irradiation in hexane with unfiltered light from a medium pressure mercury arc lamp resulted in its conversion to two products, bicyclo[4.1.0]hept-2-ene-1-carbonitrile, II, and tricyclo-[4.1.0.0.³,⁷]heptane-7-carbonitrile, III, in a 20:1 ratio. [equation removed] The structure of the major rearrangement product, II, was proven by X-ray crystallography of its crystalline derivative, 1-methylamino-bicyclo-[4.1.0]hept-2-ene-p-bromobenzenesulfonate. The m!nor product, III, was identified by catalytic hydrogenation to 7-cyanobicyclo[2.2.1]heptane and vpc comparison with authentic 7-cyanobicyclo[2.2.1]heptane synthesized from bicyclo-[2.2.1]heptane-7-carboxylic acid. The photorearrangement of I to II and III are orbital symmetry-allowed photochemical 1,3 and 1,2-sigmatropic shifts, respectively. The 1,3-sigmatropic shift has not been previously observed in the photochemistry of α,β-unsaturated nitriles while the 1,2 shift was observed in the photorearrangement of 1-cyanocyclohexenes. Further experiments are needed to determine whether or not the rearrangements are concerted or diradical in nature. Preliminary experiments on the related compound, bicyclo[3.2.0]oct-2ene-3-carbonitrile, IV, synthesized from norbornene, indicate that it probably undergoes the same type of rearrangements as I. The ratio for 1,3,to 1,2 a bond shifts seems to be 3:2 in this case. [figure removed] Doctor of Philosophy (PhD)

The photochemistry of 1- and 2-naphthonitrile with the olefins tetramethylethylene and 1,2-dimethylcyclopentene has been studied in a variety of solvents. In hexane, benzene, and 1,2-dimethoxyethane the major products in the reaction with tetramethylethylene are the cyclobutanes 1-cyano-7,7,8,8-tetramethyl-2,3-benzobicyclo[4.2.0]octa-2,4-diene (from 1-naphthonitrile) and 6-cyano-7,7,8,8-tetramethyl-2,3-benzo-bicyclo[4.2.0]octa-2,4-diene (from 2-naphthonitrile). Reaction with 1,2-dimethylcyclopentene gives cyclobutanes with analogous structures, in genzene and dimethoxyethane. In high polarity solvents, products of photoreduction are formed. 2-Naphthonitrile and tetramethylethylene upon irradiation in 2,2,2-trifluoroethanol give 1-(2'-trifluoroethoxy-1' ,1' ,2' ,2-tetramethyl)-3-cyano-1,4-dihydronaphthalene and 3,4-dihydro-2-naphtho-nitrile. Reactions in other high polarity solvents give complex mixtures of products. Stern-Volmer quenching of 2-naphthonitrile fluorescence by tetramethylethylene increases dramatically as solvent polarity increases from hexane to methanol. The Stern-Volmer constants are 0.50 M⁻¹ and 148 M⁻1 for 2-naphthonitrile fluorescence quenching in hexane and methanol, respectively. Similar, although less dramatic, behaviour is observed for 1-naphthonitrile fluorescence quenching by tetramethylethylene. Lifetimes of the luminescent exciplexes formed from 1-naphthonitrile and the olefins have been measured in the lower polarity solvents. With both teframethyl-ethylene and 1,2-dimethylcyclopente, the exciplex lifetimes increase, level off, and then decrease with increasing solvent polarity. For the 1-naphthonitrile-tetramethylethylene exciplex, the measured lifetimes are 3.75, 10.4, 12.6, 12.7, and 4.7 ns in hexane, benzene, dimethoxyethane, tert-butanol, and iso-propanol, respectively. The photochemistry and photophysics of the naphthonitrile-olfein systems are discussed in terms of a changing quenching mechanism with increasing solvents polarity. It is proposed that quenching in non-polar solvents involves exciplex formation, while in polar media electron transfer occurs. The results are discussed within the context of models for exciplex formation and decay introduced by Weller and Michl. Doctor of Philosophy (PhD)

The thesis consists of two parts, which have been combined in the Introduction and Discussion sections. Part A. Isoindenes Transient isoindenes absorbing in the 400-550 nm range have been observed in the flash photolysis of a series of 1,1-diarylindenes. They have been studied by ultraviolet spectroscopy, low temperature nmr, chemical trapping, and flash photolysis techniques. Irradiation of 1,1,3-triphenyl-indene at 254 nm in cyclopentane at -70ºC gives an orange solution (λ max 478 nm) which contains 1,2,3-triphenylisoindene whose methine and vinylic proton resonances in the nmr occur at 4.45 and 6.80 ppm respectively. Reaction of 1,2,3-triphenylisoindene with 4-phenyl-1,2,4-triazoline-3,5-dione at -70°C, gave a Diels-Alder adduct. The isoindene formed 1,2,3-triphenylindene quantitatively on warming to 20°C. The kinetics of the 1,5-hydrogen shift by which a series of isoindenes rearrange to stable indenes were studied by flash photolysis. The transient decay was first order, and rate constants (deoxygenated hexane, 20°C) are: 1,2-diphenylisoindene, 36 s⁻¹; 1-phenyl-2-p-cyanophenylisoindene, 14 s⁻¹; 1-phenyl-2-p-bromophenylisoindene, 27 s⁻¹; 1-phenyl-2-p-methoxyphenylisoindene, 44 s⁻¹ and 1,2,3-triphenylisoindene, 1.21 s⁻¹. Kinetic isotope effects of kH/kD = 3.7 and 6.5 for the decay of 1,2,3-triphenylisoindene and 1,2-diphenylisoindene (2-H and 2-D) respectively show that the H-shift is rate determining. The 1,5-hydrogen shift in 1,2-diphenylisoindene has Ea = 13.1 kcal/mol and ΔSº† = -9.0 eu, and in 1,2,3-triphenylisoindene has Ea = 11.8 kcal/mol and ΔSº‡= -19.6 eu. The ground state energy of isoindene relative to indene is estimated to be 20 kcal/mol, which is compared with theoretically calculated values. Part B. o-Xylylenes o-Xylylene derivatives have been generated in the flash photolysis of four indan-2-ones. Thus, 1,1,3,3-tetramethylindan-2-one gives 7,7,8,8- tetramethyl-o-xylylene while 1,1-dimethylindan-2-one gives 7,7-dimethyl-o-xylylene. Both these transients decay (thermally and photochemically) by a 1,5-hydrogen shift to yield alkyl isopropenylbenzenes. The rates of thermal decay are 0.002 s⁻¹ and 0.038 s⁻¹, for the tetra- and dimethyl compounds respectively, at ca. 20°C in deoxygenated hexane. The decay of tetramethyl-o-xylylene showed a kinetic isotope effect (kH/kD) of 5.4. Activation parameters were: Ea= 19 kcal/mol, ΔSº‡= -7.7 eu (tetramethyl o-xylylene); Ea= 15.5 kcal/mol, ΔSº‡= -13.9 eu (dimethyl-o-xylylene). Low temperature photolysis (-70°C, 254 nm) show absorption maxima at 350nm, for the tetramethyl compound, and 360 nm for the dimethyl compound. Photolysis of 1,1,3,3-tetramethyl-4,5-benzindan-2-one gives the thermally stable 9,9,10,10-tetramethyl-1,2-naphthoquinodimethane, which decays photochemically to 1-isopropenyl-2-isopropylnaphthalene. A transient with a lifetime of about 1 μs could be observed in the flash photolysis of 1,1,3,3-tetramethyl-5-6-benzindan-2-one, which gives two photoproducts, 2-isopropyl-3-isopropenylnaphthalene and 3,3,4,4-tetramethylnaphtho[b]cyclo-butene. The rates of thermal decay of the transients are consistent with thermochemical calculations. Spectroscopic evidence, together with theoretical calculations, indicates that the transients are twisted about the 'essential' single bonds of the non-aromatic ring, and cannot adopt the planar geometry necessary for the allowed suprafacial 1,5-H shift. This together with the photolability of the transients, suggests that the thermal decay maay involve the previously unknown antarafacial 1,5-hydrogen shift. Doctor of Philosophy (PhD)

Photoreaction of naphthalene with pyrrole in various solvents has been studied. The major products are 2-(l,4-dihydro-l-naphthyl)-pyrrole and 2-(1,2-dihydro-2-naphthyl)-pyrrole which together comprise 85% of the products mixture. Solvent dependence of both products ratio and quenching of naphthalene fluorescence have also been investigated. The evidence suggests that the reaction is initiated by charge transfer from pyrrole to the lowest excited singlet naphthalene followed by a proton shift from the N-position of pyrrole to a negative charge center in the naphthalene ring. Using N-deuteriopyrrole in the reaction, it was found that deuterium is incorporated at the naphthalene ring in the products. Further evidence to support the proton shift mechanism is that N-methylpyrrole quenches naphthalene fluorescence as efficiently as pyrrole, but the reaction does not take place. The photoreaction of l-cyanonaphthalene with tetramethylethylene in methanol and benzene have been studied. Substitution products were found in methanol solution but a cyclo-adduct was formed in benzene. Tetramethylethylene quenches fluorescence of l-cyanonaphthalene both in methanol and benzene. In contrast, 2-cyanonaphthalene only reacts with tetramethylethylene in methanol to give substitution products with one mole of methanol incorporated. The failure of reaction in benzene is consistent with the absence of fluorescence quenching in that solvent; in methanol, quenching occurs at the diffusion controlled limit. Doctor of Philosophy (PhD)