Which of the following fatty acids does NOT form soap?

Soap is primarily made from a combination of saturated and unsaturated fatty acids. The eight fatty acids that contribute to soap molecules include four saturated ones (myristic, lauric, palmitic, and stearic) and four unsaturated ones (ricinoleic, oleic, linoleic, and linolenic). Butyric acid isn't commonly used in soap making due to its distinct odor and properties.