Question

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

Short answer

Answer: Glyceryl trioleate has a higher melting point compared to glyceryl trilinoleate due to the greater degree of saturation in its fatty acid content. The monounsaturated fatty acid, oleic acid, in glyceryl trioleate allows for a more linear structure and closer molecular packing, resulting in a higher melting point. In contrast, the polyunsaturated fatty acid, linoleic acid, in glyceryl trilinoleate introduces more kinks in the structure, reducing the ability to pack closely, and thus leading to a lower melting point.

Step-by-step solution

Understand the chemical structure of glyceryl trioleate and glyceryl trilinoleate

First, let's understand the chemical structures of glyceryl trioleate and glyceryl trilinoleate. Both compounds are glycerides, which are esters of glycerol and fatty acids. Glyceryl trioleate is composed of glycerol and three oleic acid (C18:1) molecules, while glyceryl trilinoleate is composed of glycerol and three linoleic acid (C18:2) molecules.

Analyze the effects of fatty acid saturation on melting point

The main difference between oleic acid and linoleic acid is the number of double bonds. Oleic acid is monounsaturated with one double bond (C18:1), while linoleic acid is polyunsaturated with two double bonds (C18:2). In general, the more double bonds in a fatty acid, the lower its melting point. This is because the presence of double bonds introduces kinks in the fatty acid chains, making it more difficult for the molecules to pack closely together and form a more solid, ordered structure.

Compare the melting points of glyceryl trioleate and glyceryl trilinoleate

Given that glyceryl trioleate is formed with oleic acid, which is a monounsaturated fatty acid, its structure will be more linear compared to that of glyceryl trilinoleate with linoleic acid, which is a polyunsaturated fatty acid. As a result, glyceryl trioleate molecules will be able to pack more closely together and form a more ordered structure, leading to a higher melting point.

Conclusion

Based on the effects of fatty acid saturation on molecular packing and melting point, glyceryl trioleate is expected to have a higher melting point compared to glyceryl trilinoleate.