Phototransformation of 2,6-dichloroaniline in aqueous solution

Three photoproducts were identified in an air-saturated irradiated aqueous solution of 2,6-dichloroaniline (2,6-DCA): 2-amino-3-chlorophenol (1), 2-am ino-1-chlorophenoxazin-3-one (2) and 2-amino-1,9-dichlorophenoxazin-3-one ( 3). 1 is the main primary photoproduct: its initial chemical yield is highe r than 65%. Its formation is influenced neither by oxygen nor by pH in the range 3.6-11.2. It results from the photohydrolysis of 2,6-DCA. It may be n oted that no formation of chlorocyclopentadiene carbonitrile was observed, whereas the contraction of the ring is a significant pathway with 2-chloroa niline. Two other photoproducts namely 2-aminophenol (4) and 2-aminophenoxa zin-3-one (5) were also formed in deoxygenated solutions. Compounds 2, 3 an d 5 are formed in the second stage and result from the excitation of 1, but they appear at relatively low conversion extent. A mechanism involving an o-benzoquinone monoimine (o-BQMI) is proposed to explain their formation. ( C) 1999 Elsevier Science S.A. All rights reserved.