3,3 -Dimethyl-4-methoxybenzophenone

Two UV filters (used to block UV-rays in sunscreens and other products), octyl-p-methoxycinnamate and octyl-dimethyl-p-aminobenzoate, reacted with chlorine, producing chlorine-substituted compounds as intermediates that finally cleaved to smaller ester products [121]. Some of the identified octyl-p-methoxycinnamate DBPs showed weak mutagenic properties. Chlorinated and brominated intermediates were formed during chlorination of 2-ethylhexyl-4-(dimethylamine)benzoate and 2-hydroxy-4-methoxybenzophenone, with trichloromethoxyphenol the most abundant DBP [122]. 

A number of LC—MS/MS based methods have been developed for their trace analysis in environmental samples. For water analysis, LC—ESI—MS/MS is the technique of choice however, in recent studies, UHPLC separation and APCI ionization has become increasingly popular. Pedrouzo et al. [78] developed a new UHPLC—MS/MS method using solventless stir-bar sorptive extraction to investigate four UV filters, dihydroxy methoxybenzophenone (DHMB), benzophenone-3 (BP-3), octocrylene (OC), and ethylhexyl dimethyl-aminobenzoate (OD-PABA) in surface water and wastewater. Detection limits of 2.5 ng/1 and 10 ng/1, respectively, were achieved. Recently, Wick, Fink, and Temes combined LC—ESI—MS/MS and LC—APCI—MS/MS after SPE extraction for the determination of five UV filters in wastewater and surface water [79]. Quantification limits achieved ranged from 0.5 to 5 ng/I and 2.5 to 50 ng/I in surface water and wastewater, respectively. An innovative method, more simple and rapid, based on the direct analysis of the surface of a polydimethylsiloxane-coated stir bar previously used to extract the UV filters from water was developed by Flaunschmidt et al. [80]. With this direct analysis in real time (DART) —MS method, seven UV filters were... 

Also obtained by reaction of dimethyl sulfate with 2,3-dihydroxy-4-methoxy-benzophenone or with 2,4-dihydroxy-3-methoxybenzophenone in the presence of alkali [379],... 

Preparation by partial methylation of 2,5-dihy-droxy-4-methoxybenzophenone with dimethyl sulfate in the presence of potassium carbonate in refluxing acetone [656,760]. 

Preparation from 4-fluoro-4 -methoxybenzophenone by reaction under nitrogen with potassium hydroxide in aqueous dimethyl sulfoxide at 60° for 18 h [170]. 

Preparation by demethylation of 3,4-dimethyl-4 -methoxybenzophenone with boiling pyridinium chloride (80%) [1005]. 

Preparation by saponification of 3 -(acetyloxy)-2,4-di-methoxybenzophenone (SM) with sodium hydroxide in refluxing dilute ethanol for 30 min [990]. SM was obtained by Friedel-Crafts acylation of resorcinol dimethyl ether with m-acetoxybenzoyl chloride in the presence of aluminium chloride in carbon disulfide at 0° for 20 h (10%). m.p. 163° [990] Spectra (NA). 

The 4 -chloro-4,6-dimethyl-2-methoxybenzophenone obtained (27%) by demethylalion with 48% hydrobromic acid gave the expected ketone [904],... 

Obtained, in mixture with 2 -hydroxy-2,3, 4-tti-methoxybenzophenone, by reaction of 2,3-di-methoxybenzoyl chloride with resorcinol dimethyl ether in ethyl ether in the presence of aluminium chloride for 8 h at r.t. (total yield 54%) [1010]. 

Alkoxyhydroxybenzophenonesulfonic acids are used in the manufacture of cosmetic sunscreen additives they are synthesized by sulfonation of the parent alkoxyhydroxybenzophenones with chlorosulfonic acid at temperatures in the range (—20 to 100 °C) using an aliphatic or aromatic ester solvent. " For instance, 2-hydroxy-4-methoxybenzophenone reacts with chlorosulfonic acid (2.6 equivalents) in ethyl acetate at 0-5 °C (30 minutes), then at room temperature (12 hours) to yield 4-hydroxy-2-methoxybenzophenonesulfonic acid (80%). " The sulfonation may also be effected in excellent yield (95.3%), by reacting the substrate with an equimolar amount of chlorosulfonic acid in dimethyl carbonate at 10-35 °C (1 hour). " In this example, of course, the sulfonation is greatly... 

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