PHOTOCHEMISTRY OF DIBENZOYL METHANE UVA FILTERS .1.

Two dibenzoyl methane derivatives, 4-isopropyldibenzoyl methane (I-DBM) and 4-t-butyl-4'-methoxydibenzoyl methane (BM-DBM), have been found to be photolabile towards UVA light in non-polar solvents, whereas in polar solvents photodegradation was very low. In each case about a dozen photoproducts were identified: their formation involves primary alpha bond cleavages of carbonyl groups, followed by hydrogen abstraction and/or oxidation or radical recombination. These photoproducts can be classified as substituted benzaldehydes, benzoic acids, acetophenones, phenylglyoxals, benzils, dibenzoyl methanes or dibenzoyl ethanes.