Crystal structure of cholestanyl caprylate and binary phase behavior with cholesteryl caprylate

Area of Science:

• Crystallography
• Materials Science
• Organic Chemistry

Background:

• Cholestanyl n-octanoate (caprylate) is a sterol ester with potential applications in materials science.
• Understanding its crystal structure and phase behavior is crucial for predicting its properties and interactions.

Purpose of the Study:

• To determine the crystal structure of cholestanyl caprylate.
• To analyze its molecular conformation and packing in the solid state.
• To investigate the phase equilibria of the cholestanyl caprylate/cholesteryl caprylate binary system.

Main Methods:

• Single-crystal X-ray diffraction was used to collect diffraction data.
• Direct methods and block-diagonal least squares refinement were employed for structure determination.
• Phase equilibria were studied using a combination of techniques, likely including thermal analysis.

Main Results:

• The crystal structure is monoclinic (space group A2) with specific cell dimensions and two molecules in the asymmetric unit.
• Molecules exhibit extended conformations with variations in ester bond rotation and C17 chains.
• Molecular packing forms stacked bilayers with distinct arrangements of sterol and caprylate chains.
• The cholestanyl caprylate/cholesteryl caprylate system shows limited mutual solubility, a eutectic point at 73% cholestanyl caprylate, and monotropic cholesteric mesophase behavior.

Conclusions:

• The crystal structure of cholestanyl caprylate is elucidated, highlighting its unique packing and conformational features.
• Significant differences exist between cholestanyl caprylate and cholesteryl caprylate crystal structures.
• The binary system exhibits complex phase behavior with implications for material properties and potential applications.