Disordered fatty-acid chains in piperazinium myristate and palmitate

(I) Piperazinium n-tetradecanoate (myristate), C4H12N2(2+).2C14H27O2-, Mr = 542.85, m.p. = 368.9 K, triclinic, P1, a = 5.681 (1), b = 7.454 (1), c = 20.676 (3) A, alpha = 84.59 (1), beta = 86.37 (1), gamma = 81.73 (1) degrees, V = 861.5 A3, Z = 1, T = 296 K, Dm = 1.05, Dx = 1.05 g cm-3, F(000) = 304, Mo K alpha, lambda = 0.7107 A, mu = 0.723 cm-1, R = 0.062 for 2198 independent reflections with I greater than sigma (I). (II) Piperazinium n-hexadecanoate (palmitate), C4H12N2(2+).2C16H31O2-, Mr = 598.95, m.p. = 370.2 K, triclinic, P1, a = 5.678 (1), b = 7.472 (1), c = 22.916 (3) A, alpha = 84.64 (1), beta = 89.82 (1), gamma = 81.32 (1) degrees, V = 956.8 A3, Z = 1, T = 296 K, Dm = 1.04, Dx = 1.04 g cm-3, F(000) = 336, Mo K alpha, lambda = 0.7107 A, mu = 0.708 cm-1, R = 0.052 for 1931 independent reflections with I greater than sigma (I). These crystal structures, together with the previously reported n-decanoate and n-dodecanoate (laurate) salts, form an isostructural series. The piperazinium cations, which have a crystallographic centre of symmetry, are in the chair conformation. Each cation forms a salt bridge to four different anions with N ... O distances ranging from 2.67 to 2.70 A. The alkanoate chains are bent with torsion angles of 78.6 degrees (I) and 79.7 degrees (II) at the C3-C4 bond. The longer sections of the alkanoate chains are close-packed together in an antiparallel array.(ABSTRACT TRUNCATED AT 250 WORDS)