The hydrogen-bonding patterns of 3-phenyl-propyl-ammonium benzoate and 3-phenyl-propyl-ammonium 3-iodo-benzoate: Generation of chiral crystals from achiral mol-ecules

The crystal structures and hydrogen-bonding patterns of 3-phenyl-propyl-ammonium benzoate, C₉H₁₄N ⁺·C₇H₅O₂ ^-, (I), and 3-phenyl-propyl-ammonium 3-iodo-benzoate, C₉H₁₄N ⁺·C₇H₄IO₂ ^-, (II), are reported and compared. The addition of the I atom on the anion in (II) produces a different hydrogen-bonding pattern to that of (I). In addition, the supra-molecular heterosynthon of (II) produces a chiral crystal packing not observed in (I). Compound (I) packs in a centrosymmetric fashion and forms achiral one-dimensional hydrogen-bonded columns through charge-assisted N - H⋯O hydrogen bonds. Compound (II) packs in a chiral space group and forms helical one-dimensional hydrogen-bonded columns with 21 symmetry, consisting of repeating R ₄ ³(10) hydrogen-bonded rings that are commonly observed in ammonium carboxyl-ate salts con-tain-ing chiral mol-ecules. This hydrogen-bond pattern, which has been observed repeatedly in ammonium carboxyl-ate salts, thus provides a means of producing chiral crystal structures from achiral mol-ecules.