Triglyceride molecules have three chains and a glycerol, residue, and—
for the same subcell—packing of the moleculescan occur in several ways.
Some of these are shown in Figure 15.19b. In all configurations, the
molecules form regularly stacked double layers. The variation concerns:
The tilt of the chains with respect to the plane of the layers. Ina
crystals the angle is 90 8.
The double layers can span two or three of the paraffin chains,
denoted L2 and L3. Both configurations can occur inb^0 andb
crystals.
If one of the three fatty acid residues is (much) shorter than the other
two, an L3 conformation is obtained, as illustrated for SCS.FIGURE15.19 Crystal structure in various polymorphs. (a) Packing modes of
paraffinic chains. The straight lines indicate the cross section of the subcell. (b)
Packing modes of triglyceride molecules.