The reaction of a fatty acid with NaOH is known as saponification. Saponification is a chemical process that converts fats and oils into soap and glycerol. The reaction involves the hydrolysis of the ester bonds in the fatty acids, resulting in the formation of carboxylate salts (soaps) and glycerol.

The general chemical reaction for saponification can be represented as follows:

Triglyceride (fat or oil) + 3 NaOH (sodium hydroxide) → 3 Fatty acid salts (soaps) + Glycerol

In this reaction, the triglyceride, which is a molecule composed of three fatty acid chains attached to a glycerol backbone, reacts with sodium hydroxide, a strong base. The sodium hydroxide breaks the ester bonds between the fatty acids and glycerol, releasing the fatty acids as carboxylate salts. These carboxylate salts are what we commonly refer to as soaps. Glycerol, a byproduct of the reaction, is a viscous liquid that has its own commercial uses.

The soaps produced through saponification are typically sodium salts of fatty acids, although they can also be potassium or ammonium salts. The type of fatty acid present in the starting triglyceride determines the properties and characteristics of the resulting soap. Soaps made from saturated fatty acids, such as those found in animal fats, tend to be harder and more solid, while soaps made from unsaturated fatty acids, such as those found in vegetable oils, are softer and more liquid.

Saponification is a widely used process for producing soap and other personal care products, such as shampoo, conditioner, and body wash. It is also employed in the manufacture of industrial products like lubricants, paints, and detergents.