Structure of mono-acid even-numbered beta-triacylglycerols.

The crystal structure of the beta polymorph of tripalmitin (1,2,3-trihexadecanoylglycerol, beta-PPP) has been determined by single-crystal X-ray diffraction. The molecules crystallize in space group P1; in an asymmetric tuning-fork conformation. This structure and the already-known crystal structures of beta-tricaprin (beta-CCC) and beta-trilaurin (beta-LLL) could be matched in an overlap model. Apart from a difference in chain length, the three structures are almost identical. The overlap model can be used to predict the crystal structure of the other members of the C(n)C(n)C(n)-type (n = even) TAG series reasonably accurately. This is demonstrated by predicting the crystal structure for beta-trimyristin (beta-MMM) and successively comparing the experimental and calculated X-ray powder diagrams.