4-Ammonio-5-methoxy-2-methylbenzenesulfonate

The title compound, C8H11NO4S, crystallizes as a zwitterion, with the negatively charged benzenesulfonate group and the positively charged NH3+ group in mutually para positions. All the non-H atoms, except for one O atom of the sulfonate group, lie on a crystallographic mirror plane (Z′ = 1/2). In the crystal, the hydrogen-bonding structure is two-dimensional, propagating in the c-axis direction through a bifurcated hydrogen bond between the NH3+ and the SO3− groups, and in the b-axis direction through an R22(16) ring motif involving the same functional groups. This latter hydrogen bonding is supported by offset π–π interactions [intercentroid distance = 3.8114 (4) Å]