C4H9 is a chemical formula representing a group of organic compounds known as butyl groups. These compounds consist of four carbon atoms and nine hydrogen atoms, making them part of the alkane family. The butyl group can exist in different structural forms, including n-butyl, isobutyl, sec-butyl, and tert-butyl, each with unique properties and applications. These butyl compounds are commonly used in various industries, including plastics, solvents, and fuels. They play a significant role in the production of materials like rubber and adhesives, contributing to everyday products and industrial processes.