The photochemical [2+2] cycloaddition of 2-adamantanone (AD) with trans-dicyanoethylene (t-DCE) was studied in acetonitrile as a function of pressure, and the activation volumes for both singlet and triplet reactions were determined. The competing reactions between excited singlet and triplet states of AD were found to be pressure dependent. At high pressure, the intersystem crossing rate, kst, from singlet to triplet increased, and as a result the singlet lifetime of AD was shortened and the triplet reaction which leads to cis-trans isomerization of the starting olefin became favored as pressure was increased. The Stern-Volmer slopes were found to correlate linearly with solvent viscosity; however, the triplet reaction (kqt/kt) correlated linearly only with the solvent dielectric constant.
|Number of pages||11|
|Journal||Journal of Photochemistry and Photobiology, A: Chemistry|
|State||Published - 1 Jan 1988|