1-Hydroxy-2,1λ⁵-benzoxarsol-3-one Monohydrate

The stereochemistry around arsenic in the title compound, 1-hydroxybenz[c][1,2]oxarsol-3-one monohydrate, C₇H₅AsO₃.H₂O, is distorted trigonal bipyramidal, the carboxylate O atom and the water molecule occupying apical positions, and the phenyl C atom, the hydroxyl group and the lone pair occupying equatorial positions. The formation of a bond between the As and carboxylate O atoms leads to the formation of a five-membered ring fused with the phenyl ring. The water molecule forms a coordinate bond with arsenic(III). The earlier assignment of the title compound as o-carboxyphenylarsonous acid is thus incorrect.

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