Editing Ethanol (section)

=== Halogenation ===
Ethanol is not used industrially as a precursor to ethyl halides, but the reactions are illustrative. Ethanol reacts with [[hydrogen halide]]s to produce [[haloalkane|ethyl halides]] such as [[ethyl chloride]] and [[ethyl bromide]] via an [[SN2 reaction|S<sub>N</sub>2 reaction]]:
:CH<sub>3</sub>CH<sub>2</sub>OH + [[hydrogen chloride|HCl]] → CH<sub>3</sub>CH<sub>2</sub>Cl + H<sub>2</sub>O
HCl requires a catalyst such as [[zinc chloride]].<ref name="s_and_h">{{cite book | first1=Andrew | last1=Streitwieser | first2=Clayton H. | last2=Heathcock | name-list-style=vanc | author-link1=Andrew Streitwieser | author-link2=Clayton Heathcock | title=Introduction to Organic Chemistry | url=https://archive.org/details/introductiontoor00stre | url-access=registration | year=1976 | publisher=MacMillan | isbn=978-0-02-418010-0}}</ref>
HBr requires [[refluxing]] with a sulfuric acid catalyst.<ref name="s_and_h" /> Ethyl halides can, in principle, also be produced by treating ethanol with more specialized [[Halogenation|halogenating agents]], such as [[thionyl chloride]] or [[phosphorus tribromide]].<ref name="m_and_b" /><ref name="s_and_h" />
:CH<sub>3</sub>CH<sub>2</sub>OH + SOCl<sub>2</sub> → CH<sub>3</sub>CH<sub>2</sub>Cl + SO<sub>2</sub> + HCl

Upon treatment with halogens in the presence of base, ethanol gives the corresponding [[haloform]] (CHX<sub>3</sub>, where X = Cl, Br, I). This conversion is called the [[haloform reaction]].<ref>{{cite book | vauthors=Chakrabartty SK | veditors=Trahanovsky WS | title=Oxidation in Organic Chemistry | pages=343–370 | publisher=Academic Press | location=New York | year=1978}}</ref>
An intermediate in the reaction with chlorine is the [[aldehyde]] called [[chloral]], which forms [[chloral hydrate]] upon reaction with water:<ref name=Ull>{{cite book | last1=Reinhard | first1=Jira | first2=Erwin | last2=Kopp | first3=Blaine C. | last3=McKusick | first4=Gerhard | last4=Röderer | first5=Axel | last5=Bosch | first6=Gerald | last6=Fleischmann | name-list-style=vanc | chapter=Chloroacetaldehydes | title=Ullmann's Encyclopedia of Industrial Chemistry | year=2007 | publisher=Wiley-VCH | location=Weinheim | doi=10.1002/14356007.a06_527.pub2 | isbn=978-3-527-30673-2}}</ref>
:4 Cl<sub>2</sub> + CH<sub>3</sub>CH<sub>2</sub>OH → CCl<sub>3</sub>CHO + 5 HCl
:CCl<sub>3</sub>CHO + H<sub>2</sub>O → CCl<sub>3</sub>C(OH)<sub>2</sub>H