A short intro to O-chem if you can filter out some of the advanced stuff is here

What vegetable oil looks like in terms of chemical symbols. The first image on the left is one shorthand way to present chemical information. It represents a triglyceride such as is typical for vegetable oils. You can burn this directly in a diesel engine but requires filtering and heating. Some women drove a greasemobile from one end of the country to the other stopping at KFC or McDonalds to fill their tanks with the waste vegetable oil. The second image is the same chemical with more info added. the third is yet another way to represent the triglyceride.

The reaction