Nitrosation of tertiary aromatic amines related to sunscreen ingredients.
Possible routes to the formation of the sunscreen contaminant, 2-ethylhexyl 4-N-methyl-N-nitrosoaminobenzoate, have been investigated in a study of the nitrosation chemistry of 2-ethylhexyl 4-N,N-dimethylaminobenzoate (Padimate-O) and related tertiary and secondary amines. Padimate-O and the corresponding ethyl ester nitrosate rapidly at 25 degrees C in either N2O3:ether or HNO2:HOAc to produce a mixture of alkyl 4-N-methyl-N-nitrosoaminobenzoate and alkyl 4-N,N-dimethylamino-3-nitrobenzoate, the former of which is the major product. The nitrosative dealkylation of these amines at this low temperature is unusual. Asymmetrical amines exhibit a preference for nitrosative demethylation (methyl versus ethyl or benzyl), but the cleavage ratios in N2O3:ether are time-dependent, suggesting competing mechanisms with different reactant kinetic orders. A radical cation route would explain the unusual reactivity, which may compete with the established nitrosative dealkylation mechanism. 2-Ethylhexyl 4-N-methyl-N-nitrosoaminobenzoate was mutagenic in two strains of Salmonella typhimurium in the Ames assay.
Loeppky
R N
RN
Department of Chemistry, University of Missouri, Columbia.
Hastings
R
R
Sandbothe
J
J
Heller
D
D
Bao
Y
Y
Nagel
D
D
D010129:4-Aminobenzoic Acid / Q000737:chemistry / Q000633:toxicity; D009153:Mutagens; D009602:Nitrosamines; D013473:Sunscreening Agents; D062366:para-Aminobenzoates
D009153:Mutagens; D009602:Nitrosamines; D013473:Sunscreening Agents; D062366:para-Aminobenzoates; D010129:4-Aminobenzoic Acid; C041981:padimate-O