Crystal and Molecular Structure of ω-Amino Acids, ω-Amino-Sulfonic Acids and Their Derivatives. VII. The Crystal and Molecular Structure of Dl-Carnitine Hydrochloride

Abstract

Abstract The crystal structure of Dl-carnitine hydrochloride, C7H15NO3·HCl, was determined by the heavy atom method using X-ray diffraction data on a Weissenberg photograph, and refined by the least-squares method to an R-factor of 0.13 for 1969 independent reflections. The crystals are monoclinic space group P21⁄c, Z=4, with a=6.77(1), b=11.41(2), c=15.10(3) Å and β=120.1(1)°. By protonation at carboxyl oxygen atom, carnitine molecule has the cationic form, N+(CH3)3CH2CH(OH)CH2COOH, with trans-zigzag skeletal configuration as similar as γ-amino-β-hydroxybutyric acid. The Cl− ion mediates between adjacent carnitine cations by two O–H···Cl− hydrogen bonds to form infinite chain elongated along the c-axis. The correlation between molecular structure and biological activity was also discussed.