What chemical process causes an oil (such as soybean oil) to become rancid?

Question

Quizplus · Accepted Answer

The chemical process that causes oils such as soybean oil to become rancid is oxidation with molecular oxygen. This process leads to the formation of free radicals which react with the double bonds in the unsaturated fatty acids present in the oil, causing it to break down and become rancid. Hydrogenation with hydrogen, hydration with water, and bromination with bromine are not processes that normally lead to oil rancidity.

What Chemical Process Causes an Oil (Such as Soybean Oil)