Date of Award


Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)



First Advisor

Mark G. Steinmetz

Second Advisor

Daniel T. Haworth

Third Advisor

Sheldon E. Cremer

Fourth Advisor

Michael A. McKinney

Fifth Advisor

Steve L. Regen


Direct photolysis of 4,4-dimethyl-1,1-diphenyl-1,2-pentadiene (1) in tert-butyl alcohol yields 1-tert-butyl-3,3-diphenylcyclopropene (2), 4,4-dimethyl-methyl-1,1-diphenyl-2-pentyne (3), and 1-tert-butyl-3-phenylindene (4). Involvement of vinylmethylene as potential intermediates in 1 photoisomerization was assessed by independent generation with cyclopropene 2, the tosylhydrazone 11 of 2,2-dimethyl-5,5-diphenyl-4-pentene-3-one, and 3-tert-butyl-5,5-diphenyl-3H-pyrazole (13). Quantum yields for direct photolysis of 2 were determined for allene 1, indene 4 and indene 5. Allene 1, cyclopropene 2 and indene 4 were products of nitrogen photoxtrusion from 13, and similiar results were obtained from the sodium salt 12 of tosylhydrazone 11. Flash vacuum pyrolysis (FVP) of 2 at 400 C produced indene 4 and 3-tert-butyl-1-phenylindene (15). FVP of indene 4 also gave 15 and recovered 4. Allene 1 was recovered in 98% yield after FVP (400 C). Deuterium labelling of photoproducts was determined for 4,4-dimethyl-1,1-diphenyl-1,2-pentadiene-3-d1 (1-d1); a (PHI)(,H)/(PHI)(,D) = 3.07 suggest that the second 1,2-H shift is rate determining as opposed to the small (PHI)(,H)/(PHI)(,D) of 1.36 for total products, 2 + 3 + 4, implicating only a low excited-state barrier in the first step. KIEs are derived. Funneling from the singlet excited state to the ground state is suggested formation of 1 in photolyses of 2. Discrete ground-state vinylmethylenes adequately account for thermolysis products. Alternative mechanisms are discussed. The direct photolysis at 185 nm (far-UV) of 1,1,3,3-tetramethyl-1,3-disilacyclopentene (1) yielded a ring contraction product 1,1,3,3-tetramethyl-2-methylene-1,3-disilacyclobutane (2) and a cleavage product, 2,4,4-trimethyl-2,4-disilahex-5-yne (3). Photolysis at 214 nm gave yields of products which accounted for a higher total, of the primary photochemistry of 1. Sensitized photolysis at 254 nm using toluene as the triplet sensitizer gave no reaction. The photolysis of disilacyclopentene 1 at 214 nm in methanol and methanol-0-d1 gave products 2 and 3 in addition to an alcohol adduct. The photoreaction was elucidated as methanol addition and cleavage to form silyether 4a. Photolysis in methanol-0-d1 led to >99% incorporation of one deuterium, exclusively at the vinyl carbon (beta) to silicon of silylether 4a, with a high degree of stereospecificity favoring H(,B). Concentration vs. time profiles are constructed and quantum yields are determined using cis-cyclooctene actinometry. Direct photolysis of vinylidenecyclobutane (1) at 185 nm produces spiro 2.3 hexene-1-ene (2), ethynylcyclobutane (3), and 3-methylenecyclobutane (4). Highly volatile products were identified as butatriene, ethylene, 1,3-butatriene (7) and vinylacetylene (8). Plots of product concentration vs time plots clearly show that 2-4, butatriene, and ethylene are primary products whereas the other volatiles, 1,3-butadiene and vinylacetylene, are secondary photoproducts, most likely of butatriene. Butatriene is rapidly converted to 1,3-butadiene and vinylacetylene upon direct irradiation (185 nm = 254 nm) in heptane. However, an upward curvature of a concentration vs time plot for the photolysis of butatriene 5 in pentane appears indicative of a free radical process. Quantum yields were determined from initial slope of concentration vs time plots using as a actinometer the cis to trans isomerization of cyclooctene.



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