PHOTOLYSIS OF SUBSTITUTED NAPHTHALENES ON SiO₂ AND Al₂O₃

Photolysis of naphthalene on the surface of SiO 2 under an atmosphere of air produces phthalic acid as the only major photoproduct, accounting for 49%o of the consumed naphthalene. Photolysis on Al 2 O 3 also produces phthalic acid, in 31% yield. Photolysis of 1 ‐methylnaphthalene on SiO 2 proceeds under similar conditions to produce 2‐acetylbenzoic acid (35%) as the major photoproduct with the production of a small amount of I‐naphthaldchyde (6%). 1‐Cyanonaphthalene does not photooxidize under similar conditions. The presence of oxygen is necessary for the photodecomposition of naphthalene and 1‐methylnaphthalene to proceed. Superoxide formed from the photolysis of naphthalene at the SiO 2 /air interface is readily observed by electron paramagnetic resonance spectroscopy. In the absence of naphthalene no superoxide is observed. A mechanism involving electron transfer from the S 1 state of the naphthalene to O 2 is proposed on the basis of these observations and related literature precedent.