Structure of strychnine hydrochloride sesquihydrate

C21H23N2O2+.Cl-.1.5H2O, Mr = 397.90, monoclinic, P2(1), a = 7.617 (1), b = 32.463 (2), c = 7.849 (1) A, beta = 90.40 (2) degrees, V = 1940.8 (4) A3 Z = 4, Dm = 1.39, Dx = 1.36 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 19.724 cm-1, F(000) = 844, final R = 0.047 for 3368 observed reflections. Strychnine hydrochloride is a naturally occurring alkaloid in its protonated form. One of the N atoms accepts the proton from hydrochloric acid changing its hybridization to sp3. The indole N atom is sp2 hybridized with its lone-pair electron involved in conjugation with the carbonyl group. The hydrogen bonds form a complex zigzag network which stabilizes the structure.