Question

Which would you expect to have the higher melting point, glyceryl trioleate or glyceryl trilinoleate?

Short answer

Glyceryl trioleate has a higher melting point than glyceryl trilinoleate because its fatty acid chains have fewer double bonds, allowing for tighter molecular packing and stronger intermolecular forces.

Step-by-step solution

Understand the molecular structures of glyceryl trioleate and glyceryl trilinoleate

Glyceryl trioleate consists of a glycerol backbone with three oleate fatty acids. Oleic acid is an unsaturated fatty acid containing one double bond between two carbon atoms. Glyceryl trilinoleate, on the other hand, has a glycerol backbone with three linoleic fatty acids, which contain two double bonds between carbon atoms.

Compare the fatty acid chains

Oleic acid in glyceryl trioleate has a single double bond, while linoleic acid in glyceryl trilinoleate has two double bonds. When a fatty acid chain has more double bonds, there are kinks in the chain. These kinks prevent the molecules from packing tightly together.

Explain the impact of molecular packing on melting points

In substances with higher melting points, the molecules are held together more tightly by stronger intermolecular forces. Strong molecular packing results in higher melting points. Kinks in the fatty acid chains, as seen in the linoleic acid of glyceryl trilinoleate, disrupt molecular packing and lead to weaker intermolecular forces, causing a lower melting point.

Identify the compound with the higher melting point

Glyceryl trioleate has a fatty acid chain with only one double bond, allowing it to pack more tightly compared to the glyceryl trilinoleate with multiple double bonds introduced by linoleic acid. Therefore, it can be concluded that glyceryl trioleate has a higher melting point than glyceryl trilinoleate.