Abstract
The crystal structure of the free base of the ubiquitous neurotransmitter serotonin is reported for the first time. The title compound, serotonin or 5-hydroxytryptamine (5-HT) [systematic name: 3-(2-aminoethyl)-1H-indol-5-ol], C10H12N2O, has one molecule in the asymmetric unit. The conformation of the ethylamino side chain is gauche–gauche [Ca—Ca—Cm—Cm and Ca—Cm—Cm—N (a = aromatic, m = methylene) torsion angles = −64.2 (3) and −61.9 (2)°, respectively]. In the crystal, the molecules are linked into a three-dimensional network by N—H⋯O and O—H⋯N hydrogen bonds.