Safflower oil is polyunsaturated, whereas olive oil is monounsaturated. Why would safflower oil have a lower melting point than olive oil?

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Welcome back, everyone. Considering the structures of fatty acids explain why sunflower oil a poorly unsaturated oil has a lower melting point. Then peanut oil, a mono unsaturated oil. So in this problem, we are considering two oils. The first one is sunflower oil, let's call it s and the second one is peanut oil. So let's call it pea. According to the context of the problem, sunflower oil is a poorly unsaturated oil. So if we visualize its side chain, it will essentially have multiple double bonds. We don't know how many, right? But essentially more than one according to the context of the problem, if it is a poorly unsaturated oil, it will have more than one double bond. We don't really know how many, of course we can find out, but it is not important for the context of the problem. So we can say more dan one double bond for peanut oil. The problem states that we have a mono unsaturated oil, which means that there is only a one double bond in the structure. And then we simply have a straight chain of carbons. So we can stay one double bond. We want to consider those structures. And we want to recall that double bonds cause kinks, right, we don't have straight chains basically because of cis trans arrangement. And generally due to cis isomers, we observe those kings. So double bonds cause kings which causes a less efficient packing or less tight packing. So the more double bonds we have the less tight packing becomes and the less tight packing becomes. Well, essentially, this means that the average distances between molecules are larger. So they basically increase because we cannot pack them tightly. And if those distances are high, it is easier for us to separate those molecules. And therefore such a structure would have a lower melting point. So essentially, we can summarize our findings. First of all, let's state that sunflower oils, oil structure contains more double bonds hands the molecules pack less tightly and this results in a lower melting point. As we already understand, a less tight packing essentially means that the average distances between molecules are higher and therefore it is easier to separate those molecules because the attraction forces between them are lower. Thank you for watching.

Safflower oil is polyunsaturated, whereas olive oil is monounsaturated. Why would safflower oil have a lower melting point than olive oil?

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Key Concepts

Fatty Acid Structure

Melting Point and Saturation

Intermolecular Forces