PHOTOCHEMISTRY OF ACETYLENIC KETONES IN MICELLAR SOLUTIONS AS STUDIEDBY PRODUCT-YIELD-DETECTED ESR AND TRANSIENT ABSORPTION TECHNIQUES

The electron spin resonance (ESR) spectra of the transient radical pai rs in the photoreduction of 1,5-diphenyl-1,4-pentadiyn-3-one (I) and 1 ,3-diphenyl-2-propyn-1-one (II) in sodium dodecyl sulfate (SDS) micell ar solutions have been obtained by using the product-yield-detected ES R (PYESR) technique. The PYESR spectra, detected by tracing the microw ave effect on the spin-adduct yield as functions of the magnetic field , show the ESR spectra of the ketyl radical of the ketone and SDS radi cal as the components of the radical pairs. In addition, the growth an d the decay processes of the radical pair were observed through detect ing the effect of microwave pulse as functions of the delay period bet ween a laser pulse and the off and on time, respectively, of a microwa ve pulse. The absorption spectra of transient species have also been o btained by using the laser flash photolysis technique. Through the ana lysis of these data and molecular orbital calculations, the role of ac etylenic groups in the photoreactivity of acetylenic ketones is discus sed.