LENGTH-SPECIFIC AND DIRECTION-SPECIFIC SOLUTE-SOLVENT INTERACTIONS AS DETERMINED FROM NORRISH-II REACTIONS OF P-ALKYLALKANOPHENONES IN ORDERED PHASES OF N-BUTYL STEARATE

The photochemistry of a series of p-alkylalkanophenones (1) has been investigated in the ordered and isotropic phases of n-butyl stearate (BS). By varying the total length of the ketones and the relative position of the benzoyl group within ketones of constant length, the solvent-related factors responsible for Norrish II product selectivity and reactivity have been identified. Specifically, the location of the hydroxy 1,4-biradical intermediates from 1 with respect to the carboxyl groups of neighboring BS molecules and the orientation of the biradical centers within a BS layer appear to control the nature and efficiency of product formation. Infrared spectra of models of the hydroxy 1,4-biradicals in BS and eicosane support the hypotheses. Differential scanning calorimetric data indicate that the ketones exhibiting the lowest product selectivity or least reactivity are not incorporated well within the BS anisotropic phases. © 1990, American Chemical Society. All rights reserved.