Haloform reaction

Haloform reaction

The haloform reaction is a chemical reaction where a haloform (CHX3, where X is a halogen) is produced by the exhaustive halogenation of a methyl ketone (a molecule containing the R-CO-CH3 group) in the presence of a base. [Chakrabartty, in Trahanovsky, "Oxidation in Organic Chemistry", pp 343-370, Academic Press, New York, 1978] R may be Hydrogen, alkyl or aryl. The reaction can be used to produce CHCl3, CHBr3 or CHI3.


Substrates which successfully undergo the haloform reaction are methyl ketones and secondary alcohols oxidizable to methyl ketones, such as isopropanol. The halogen used may be chlorine, bromine, and iodine. Fluoroform (CHF3) cannot be prepared from a methyl ketone by the haloform reaction due to the instability of hypofluorite, but compounds of the type RCOCF3 do cleave with base to produce fluoroform (CHF3); this is equivalent to the second and third steps in the process shown above.


In the first step, the halogen disproportionates in the presence of hydroxide to give the halide and hypohalide:

: X2 + OH→ XO+ X + H+ (X = Cl, Br, I)

If a secondary alcohol is present, it is oxidized to a ketone by the hypohalide:

If a methyl ketone is present, it reacts with the hypohalide in a three step process:

:(1) R-CO-CH3 + 3 OX- → R-CO-CX3 + 3 OH

:(2) R-CO-CX3 + OHRCOOH + CX3


The detailed reaction mechanism is as follows:

Under basic conditions, the ketone undergoes keto-enol tautomerization. The enolate undergoes electrophilic attack by the hypohalide (containing a halide with a formal +1 charge). When the alpha position has been exhaustively halogenated, the molecule undergoes a nucleophilic acyl substitution by hydroxide, with CX3 being the leaving group stabilized by three electron withdrawing groups. The CX3 anion abstracts a proton from either the carboxylic acid formed, or the solvent, and forms the haloform.


This reaction was traditionally used to determine the presence of a methyl ketone, or a secondary alcohol oxidizable to a methyl ketone through the iodoform test. Nowadays, spectroscopic techniques such as NMR and infrared spectroscopy are preferred because they require small samples, may be non-destructive (for NMR) and are easy and quick to perform.

Formerly, it was used to produce iodoform and bromoform and even chloroform industrially.Fact|date=September 2007

In organic chemistry, this reaction may be used to convert a terminal methyl ketone into the appropriate carboxylic acid.

It also use for test priamry, secondary alochol.

Iodoform test

When iodine and sodium hydroxide are used as the reagents, a positive reaction gives iodoform. Iodoform (CHI3) is a pale yellow substance. Due to its high molar mass due to the three iodine atoms, it is solid at room temperature (c.f. chloroform and bromoform). It is insoluble in water and has an antiseptic smell. A visible precipitate of this compound will form from a sample only when a methyl ketone is present.


The haloform reaction is one of the oldest organic reactions around [cite book | title = Strategic Applications of Named Reactions in Organic Synthesis | author = László Kürti and Barbara Czakó | publisher = Elsevier | location = Amsterdam | year = 2005 | isbn = 0-12-429785-4] . In 1822 Serullas reacted ethanol with iodine and sodium hydroxide in water to sodium formate and iodoform, called in the language of that time "hydroiodide of carbon". In 1831 Justus Liebig reported the reaction of chloral with calcium hydroxide to chloroform and calcium formate. The reaction was rediscovered by Adolf Lieben in 1870. The iodoform test is also called the Lieben haloform reaction. A review of the Haloform reaction with a history section was published 1934. [cite journal|title =The Haloform Reaction|author=Reynold C. Fuson and Benton A. Bull|journal=Chemical Reviews
volume= 15|issue= 3|year= 1934|pages= 275–309|doi= 10.1021/cr60052a001


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • haloform reaction — haloforminė reakcija statusas T sritis chemija apibrėžtis Trihalogenmetanų sintezė veikiant etanolį arba metilketonus halogenais ir šarmais. atitikmenys: angl. haloform reaction rus. галоформенная реакция …   Chemijos terminų aiškinamasis žodynas

  • haloform reaction — noun the reaction of a halogen with a methyl ketone to form a haloform …   Wiktionary

  • Réaction haloforme — La réaction haloforme est la réaction chimique consistant à synthétiser un haloforme, c est à dire un trihalogénométhane avec trois atomes halogènes identiques (chloroforme (CHCl3), iodoforme (CHI3), bromoforme (CHBr3) le fluoroforme (CHF3) ne… …   Wikipédia en Français

  • Test iodoforme — Réaction haloforme La réaction haloforme est la réaction chimique consistant à synthétiser un haloforme, c est à dire un trihalogénométhane avec trois atomes halogènes identiques (chloroforme (CHCl3), iodoforme (CHI3), bromoforme (CHBr3) le… …   Wikipédia en Français

  • Chloroform — IUPAC name …   Wikipedia

  • List of organic reactions — Well known reactions and reagents in organic chemistry include Contents: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z    See also   Ext …   Wikipedia

  • галоформ — — [http://www.eionet.europa.eu/gemet/alphabetic?langcode=en] EN haloform A haloalkane, containing three halogen atoms, e.g. iodoform, CHI3; a haloform reaction is a reaction to produce haloforms from a ketone. For example, if propanone is… …   Справочник технического переводчика

  • Ethanol — For other uses, see Ethanol (disambiguation). Grain alcohol redirects here. It is not to be confused with Neutral grain spirit. Ethanol …   Wikipedia

  • aldehyde — aldehydic, adj. /al deuh huyd /, n. Chem. any of a class of organic compounds containing the group CHO, which yields acids when oxidized and alcohols when reduced. [1840 50; < NL al(cohol) dehyd(rogenatum) dehydrogenated alcohol] * * * Any of a… …   Universalium

  • carboxylic acid — Chem. any organic acid containing one or more carboxyl groups. [1900 05; CARBOXYL + IC] * * * Any organic compound with the general chemical formula ―COOH in which a carbon (C) atom is bonded to an oxygen (O) atom by a double bond to make a… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”