The crystal structure of the zwitterionic co-crystal of 2,4-di-chloro-6-{[(3-hy-droxy-prop-yl)azaniumyl]-meth-yl}phenolate and 2,4-di-chloro-phenol.

The title compound, CHClNO·CHClO, was formed from the incomplete Mannich condensation reaction of 3-amino-propan-1-ol, formaldehyde and 2,4-di-chloro-phenol in methanol. This resulted in the formation of a co-crystal of the zwitterionic Mannich base, 2,4-di-chloro-6-{[(3-hy-droxy-prop-yl)azaniumyl]-meth-yl}phenolate and the unreacted 2,4-di-chloro-phenol. The compound crystallizes in the monoclinic crystal system (in space group ) and the asymmetric unit contains a mol-ecule each of the 2,4-di-chloro-phenol and 2,4-di-chloro-6-{[(3-hy-droxy-prop-yl)azaniumyl]-meth-yl}phenolate. Examination of the crystal structure shows that the two components are clearly linked together by hydrogen bonds. The packing patterns are most inter-esting along the and the axes, where the co-crystal in the unit cell packs in a manner that shows alternating aromatic di-chloro-phenol fragments and polar hydrogen-bonded channels. The 2,4-di-chloro-phenol rings stack on top of one another, and these are held together by π-π inter-actions. The crystal studied was refined as an inversion twin.