Crystal structure and Hirshfeld surface analysis of 1-carb-oxy-2-(3,4-di-hydroxy-phen-yl)ethan-1-aminium chloride 2-ammonio-3-(3,4-di-hydroxy-phen-yl)propano-ate: a new polymorph of l-dopa HCl and isotypic with its bromide counterpart.

The title mol-ecular salt, CHNO·Cl·CHNO, is isotypic with that of the bromide counterpart [Kathiravan (2016 ▸). E, 1544-1548]. The title salt is a second monoclinic polymorph of the l-dopa HCl structure reported earlier in the monoclinic space group 2 [Jandacek & Earle (1971 ▸).

Crystal structure and Hirshfeld surface analysis of 1-carb-oxy-2-(3,4-di-hydroxy-phen-yl)ethan-1-aminium bromide 2-ammonio-3-(3,4-di-hydroxy-phen-yl)propano-ate.

In the title mol-ecular salt, CHNO·Br·CHNO, one of the dopa mol-ecules is in the cationic form in which the α-amino group is protonated and the α-carb-oxy-lic acid group is uncharged, while the second dopa mol-ecule is in the zwitterion form. The Br anion occupies a special position and is located on a twofold rotation axis. The two dopa mol-ecules are inter-connected by short O-H⋯O hydrogen bonds.