PHOTOLYSIS OF SUBSTITUTED NAPHTHALENES ON SIO2 AND AL2O3

Photolysis of naphthalene on the surface of SiO2 under an atmosphere o f air produces phthalic acid as the only major photoproduct, accountin g for 49% of the consumed naphthalene. Photolysis on Al2O3 also produc es phthalic acid, in 31% yield. Photolysis of 1-methylnaphthalene on S iO2 proceeds under similar conditions to produce 2-acetylbenzoic acid (35%) as the major photoproduct with the production of a small amount of 1-naphthaldehyde (6%). 1-Cyanonaphthalene does not photooxidize und er similar conditions. The presence of oxygen is necessary for the pho todecomposition of naphthalene and 1-methylnaphthalene to proceed. Sup eroxide formed from the photolysis of naphthalene at the SiO2/air inte rface is readily observed by electron paramagnetic resonance spectrosc opy. In the absence of naphthalene no superoxide is observed. A mechan ism involving electron transfer from the S1 state of the naphthalene t o O2 is proposed on the basis of these observations and related litera ture precedent.