Molecular Packing Coefficients of the Homologous Series Cholesteryl Alkanoates

The properties of cholesterol derivatives are important owing to the involvement of these compounds in a myriad of industrial and biological research areas such as thermography, display devices and the formation in atherosclerosis of arterial deposits containing cholesteryl esters. Molecular structural studies of mesogens in the crystalline state have been carried out in search of a better understanding of the physical properties which lead to mesophase formation. It has been demonstrated previously for a homologous series of nematogens¹ how the molecular packing coefficients of the solid phase vary with increasing chain length and how this throws light upon the variation of other physical properties. Here, we extend this treatment to the cholesteryl alkanoates. Detailed crystal structure analysis is available for only one member of this series: cholesteryl tetradecanoate, which was studied by Craven and de Titta.² Prior to this, unit cell dimensions and space groups has been obtained for 13 members by Barnard and Lydon.³ They found the crystallography of these compounds to be complex. No overall homology of crystal structure was apparent and at least eight different types of crystal structure occur.