ON THE PHOTOLYSIS OF PHTHALIC-ACID DIALKYL ESTERS - A PRODUCT ANALYSIS STUDY

The following phthalic acid dialkyl esters were subjected to UV irradiation (lambda(inc) = 254 nm at 22-degrees-C or lambda(inc) = 240-440 nm at 40-degrees-C): phthalic acid di(2-ethylhexyl) ester (DOP), phthalic acid di(n-octyl) ester (DNOP), phthalic acid di(n-decyl) ester (DDP) and phthalic acid dimethyl ester (DMP). In all cases (except DMP) analogous major photoproducts identified by the gas chromatography-mass spectrometry (GC-MS) method are formed: 1-alkenes, alkyl alcohols, phthalic acid anhydride, 2-formyl benzoic acid esters and benzoic acid esters. Generally, the quantum yields of decomposition are quite low: phi less-than-or-equal-to 0.03. Extension of the linear alcohol chains decreases the stability: phi(-DMP)<phi(-DNOP)<phi(-DDP). In the absence of O2, DOP, which contains branches in the alcohol chains, is more stable than the isomeric DNOP containing linear alcohol chains: phi(-DOP)< phi(-DNOP).