structural:reformatting
Halogenation

Ethanol is not used industrially as a precursor to ethyl halides, but the reactions are illustrative. Ethanol reacts with hydrogen halides to produce ethyl halides such as ethyl chloride and ethyl bromide via an S 2 reaction:

HCl requires a catalyst such as zinc chloride. HBr requires refluxing with a sulfuric acid catalyst. Ethyl halides can, in principle, also be produced by treating ethanol with more specialized halogenating agents, such as thionyl chloride or phosphorus tribromide.

Upon treatment with halogens in the presence of base, ethanol gives the corresponding haloform (CHX, where X = Cl, Br, I). This conversion is called the haloform reaction. An intermediate in the reaction with chlorine is the aldehyde called chloral, which forms chloral hydrate upon reaction with water: