  2-Ethylhexyl 4-methoxycinnamate (EHMC) is one of the most commonly used
sunscreen ingredient. In this study we investigated photodegradation of EHMC in
the presence of such common oxidizing and chlorinating systems as H2O2,
H2O2/HCl, H2O2/UV, and H2O2/HCl/UV. Reaction products were detected by gas
chromatography with a mass spectrometric detector (GC-MS). As a result of
experimental studies chloro-substituted 4-methoxycinnamic acid (4-MCA),
4-methoxybenzaldehyde (4-MBA) and 4-methoxyphenol (4-MP) were identified.
Experimental studies were enriched with DFT and MP2 calculations. We found that
reactions of 4-MCA, 4-MBA and 4-MP with Cl2 and HOCl were in all cases
thermodynamically favorable. However, reactivity indices provide a better
explanation of the formation of particular chloroorganic compounds. Generally,
those isomeric forms of mono- and dichlorinated compounds which exhibits the
highest hardness were identified. Nucleophilicity of the chloroorganic
compounds precursors were examined by means of the Fukui function.
