Date of Award

Summer 1981

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Steinmetz, Mark G.

Second Advisor

Regen, Steven L.

Third Advisor

Pollard, Bruce D.

Abstract

A new photochemical rearrangement of 3-alkyl-substituted 1,1-diphenylallenes to give indenes has been studied. The rearrangement was shown to be remarkably dependent. upon the nature of the terminal alkyl substituent as evidenced by the increase in quantum yields with greater steric bulk for the following series of substituents: methyl, n-propyl, tert-butyl. In the absence of such alkyl substitution, oligomerization is observed. The rearrangement is most likely derived from the singlet excited state since triplet sensitization led to no observation of indenes. A mechanism involving vinylcarbene intermediates deriving from 1,2- hydrogen or alkyl shifts in excited allene or cyclopropylidene seems plausible. For 1,1-diphenyl-1,2-hexadiene, 3- phenyl-1-a-propylindene and 3-phenyl-2-a-propylindene are primary products as confirmed by our study of product ratios at low conversion. The former indene is the major product consistent with preferential formation of the more stable of the two possible vinylcarbenes proposed, i.e., that resulting from 1,2-hydrogen migration.

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