MOLECULAR-CONFORMATIONS AND CRYSTAL PACKING PROPERTIES OF 5 4-ALKYL-N-(4-CYANOPHENYL)PIPERIDINES BY X-RAY-DIFFRACTION - A SURPRISING DEPENDENCE UPON ALKYL CHAIN-LENGTH

The molecular structure and crystal packing of a homologous series of 4-n-alkyl-N-(4-cyanophenyl)piperidines (I), where alkyl equals butyl, pentyl, hexyl, heptyl and octyl (n = 4-8), have been analyzed. Althoug h the conformations of the (cyanophenyl)piperidyl unit remain fairly c onstant throughout, the crystal packing depends acutely upon alkyl cha in length with one, two or four molecules comprising the asymmetric un it: for (I) (n = 4), monoclinic (P2(1)); for (I) (n = 5), monoclinic ( P2(1)/c); for (I) (n = 6), triclinic (P ($) over bar 1); for (I) (n = 7), triclinic (P ($) over bar 1); for (I) (n = 8), monoclinic (P2(1)/c ). The piperidyl rings are in a chair conformation. Unit-cell and othe r crystal data are presented.