Dual Chlorine-Bifurcated Acceptor Cl···H–(N,O) Hydrogen Bonds in 4-[(4-Methylpiperazin-1-yl) Methyl]benzoic Acid Dihydrochloride Hemihydrate
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- Jasinski, J.P., Butcher, R.J., Mallesha, L. et al. J Chem Crystallogr (2009) 39: 773. doi:10.1007/s10870-009-9565-5
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The title compound, a salt of C13H20O22+ 2Cl− 0.5 H2O, (I), crystallizes in the monoclinic space group C 2/c with unit cell parameters a = 34.091(4) Å, b = 7.2312(4) Å, c = 12.5827(5) Å, β = 96.870(6)°, Z = 8. The dihedral angle between the mean plane of the benzyl ring and the piperazin-1-yl group is 80.4(2)°, while the angle between the mean planes of the carbonyl group with that of the benzyl and piperazin-1-yl rings measure 6.6(3)° and 76.8(3)°, respectively. A short C=O and slightly extended C–O carboxyl bond in concert with weak intermolecular C–O···Cg π-ring interactions influences this twist angle with the benzyl ring and provides a slight interaction with the π conjugation of the benzene ring. Hydrogen bonding has no effect on the carboxylic group. Two separate two-center (acceptor bifurcated) Cl−···H–(N,O) hydrogen bonds are observed between one chloride anion and a water molecule and the piperazin-1-yl ring and a second chloride anion with a carboxyl oxygen atom and the piperazin-1-yl ring. These direct intermolecular couplings link the molecule into chains along the  plane of the unit cell which influence the twist angles of the benzyl and piperazin-1-yl rings and help stabilize crystal packing in the unit cell.