I. Synthesis and Decomposition of Several 2,3-Diazabicyclo[3.1.0]Hex-2-Enes. II. Wavelength Effects in Piperylene Photoisomerization

Citation

Eaton, David Fielder (1972) I. Synthesis and Decomposition of Several 2,3-Diazabicyclo[3.1.0]Hex-2-Enes. II. Wavelength Effects in Piperylene Photoisomerization. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/p0z8-6a02. https://resolver.caltech.edu/CaltechETD:etd-02112009-145526

Abstract

Part I: The synthesis and characterization of several methyl substituted 2,3-diazabicyclo[3.1.0]hex-2-enes are described. The thermal and photochemical decomposition of stereochemically labeled pyrazolines has been shown to afford mixtures of hydrocarbon products with a high degree of stereoselectivity. The nature of the products from exo- and endo-4-exo-6-dimethy1-2,3-diazabicyclo-[3.1.0]hex-2-ene suggests that carbene intermediates are formed, and multiple mechanisms for decomposition are proposed to account for the observation that the product distributions obtained are temperature dependent. A formal 1, 3-dipolar cycloreversion to afford an acyclic diazo compound, which decomposes to a carbene under the reaction conditions, is proposed to compete with formation of diradical intermediates. Part II: Initial quantum yields of trans—>cis and cis—>trans isomerization of trans- and cis-1, 3-pentadiene have been determined in pentane solutions for four excitation wavelengths in the range 236-254 nm. The photoisomerization efficiency was found to decrease markedly when high energy excitation was employed. Analysis of the data suggests that contributions of s-cis conformations may only be important for 254 nm excitation and that the bulk of the diminution in isomerization quantum yield as the initial excited state energy content is increased must be accounted for in terms of enhanced radiationless decay probabilities. Several possible mechanisms are discussed.

Thesis Files