Crotonic Acid (CAS No. 107-93-7; Chemical Formula: C₄H₆O₂) is a colorless to white crystalline solid with a sharp odor. It is an unsaturated carboxylic acid, soluble in water, alcohol, and ether. Commonly used as a monomer or intermediate in resins, plastics, and pharmaceutical synthesis. Purity is typically ≥98%.