(2E)-2-(2-Phenyl­hydrazin-1-yl­idene)propanoic acid

The 13 non-H atoms comprising the title compound, C(9)H(10)N(2)O(2), are close to planar (r.m.s. deviation = 0.140 Å), with maximum deviations of 0.292 (1) and 0.210 (1) Å to either side of the least-squares plane exhibited by the hy­droxy and carbonyl O atoms, respectively. The observed conformation is stabilized by an intra­molecular O—H⋯N hydrogen bond. The conformation about the N=C double bond [1.2909 (16) Å] is E. The hy­droxy OH group also forms an inter­molecular hydrogen bond to a carbonyl O atom, and the amine H atom similarly forms an N—H⋯O hydrogen bond to a second carbonyl O atom. The result is the formation of a double layer with a flat topology. Layers stack along the a-axis direction connected by C—H⋯π inter­actions.