Collect. Czech. Chem. Commun. 1993, 58, 142-152

Selectivity in the Photoproduct Ratios from Norrish II Reactions of a Homologous Series of 2-Alkanones in Their Melt and Solid Phases. Comparison with Other Environments

Richard G. Weiss, Sosale Chandrasekhar and Patricia M. Vilalta

Department of Chemistry, Georgetown University, Washington, DC 20057, U.S.A.


The product ratios from Norrish II reactions of 2-tridecanone, 2-tetradecanone, 2-pentadecanone, 2-hexadecanone, 2-heptadecanone, and 2-nonadecanone have been measured at low percents of conversion in the melt and solid phases. Although elimination/cyclization photoproduct ratios from the neat crystals are > 60 in optimal cases, the ratios of cyclobutanol diastereomers (cyclization products) remain near those observed from melt irradiations. From comparisons of the photoproduct selectivities in the neat solids and in their solid solutions, where the solvent molecules are similar in size and shape to the 2-alkanones, it is concluded that the crystalline lattices of some foreign hosts offer environments to the pre-product biradical intermediates, which are at least as restrictive as the environments of the solid 2-alkanones.