Butyric acid

Butyric acid (C₃H₇ CO₂H) is a fatty acid found especially in rancid butter that has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether).

There are two metameric butyric acids, called in distinction the normal- and iso-butyric acid. The normal butyric acid is the one common in rancid butter.