The reaction of butanol (C₄H₉OH) with thionyl chloride (SOCl₂) produces butyl chloride (C₄H₉Cl), sulfur dioxide (SO₂), and hydrogen chloride (HCl).

Here's the balanced chemical equation:

C₄H₉OH + SOCl₂ → C₄H₉Cl + SO₂ + HCl

This reaction is a common method for converting alcohols to alkyl chlorides. The thionyl chloride acts as a chlorinating agent, replacing the hydroxyl group (-OH) of the alcohol with a chlorine atom (-Cl). The sulfur dioxide and hydrogen chloride gases are byproducts of the reaction.