Ammonium 4-methoxycinnamate

In the title compound, NH₄⁺±C ₁₀H₉O₃^-, bimolecular layers of the anions are formed between layers of the cations. There are N - H⋯ O hydrogen bonds between the ammonium ion and the carboxylate groups of the anions. In the crystal structure, the C=C moiety of the cinnamate ion makes an angle of 117.1 (2)° with that of the nearest neighbour, indicating that a pedal rotation is required before ß-type [2+2]-photodimeriza tion can take place, which is the predominant mode of the photochemistry of this compound.