Ammonium 4-methoxycinnamate.

In the title compound, NH4+.C10H903 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 βtype [2+2]-photo-dimerization can take place, which is the predominant mode of the photochemistry of this compound. [ABSTRACT FROM AUTHOR]