STRUCTURE OF 4-HYDROXYPHENYLARSONIC ACID AND 4-METHOXY-3-NITROPHENYLARSONIC ACID

4-Hydroxyphenylarsonic acid 1 crystallizes in the monoclinic space group P2 1 /c. Four molecules are localized in a unit cell of dimensions a = 5.739(1); b = 7.226(2); c = 17.856 (2) Å; β = 90.74(2)°. The arsenic atom is tetrahedrally connected to one carbon and three oxygen atoms with the average angle around it being 109.3°. There is an extensive hydrogen bond system, involving every phenolic and arsonic acid group. 4-Methoxy-3-nitrophenylarsonic acid 2 crystallizes orthorhombic in the space group Pbca with eight molecules in a unit cell of dimensions a = 6.883 (3); b = 14.659 (7); c = 18.67 (I) Å. The arsenic atom is also tetrahedrally connected to one carbon and three oxygen atoms with the average angle around it being 109.2°. The molecules of 2 are linked along axis x through O...O hydrogen bonds between the oxygen atoms of the arsonic acid groups in endless chains.