ハロゲン化

関: bromination、chlorination、fluorination、halogenate、iodination

WordNet

the addition or substitution of chlorine in organic compounds
disinfection of water by the addition of small amounts of chlorine or a chlorine compound
the substitution or addition of iodine atoms in organic compounds

PrepTutorEJDIC

塩素処理;塩素殺菌

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/07/04 05:00:44」(JST)

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Halogenation is a chemical reaction that involves the addition of one or more halogens to a compound or material. Dehalogenation is the reverse of halogenation and results in the removal of a halogen from a molecule.^[1] The pathway and stoichiometry of halogenation depends on the structural features and functional groups of the organic substrate, as well as on the specific halogen. Inorganic compounds such as metals also undergo halogenation.

1 Organic chemistry
- 1.1 Halogenation by reaction type
  - 1.1.1 Free radical halogenation
  - 1.1.2 Addition of halogens to alkenes and alkynes
  - 1.1.3 Halogenation of aromatic compounds
  - 1.1.4 Other halogenation methods
- 1.2 Halogenation by halogen type
  - 1.2.1 Fluorination
  - 1.2.2 Chlorination
  - 1.2.3 Bromination
  - 1.2.4 Iodination
2 Inorganic chemistry
3 Chemical dehalogenation
4 See also
5 References

Organic chemistry

Halogenation by reaction type

Several pathways exist for the halogenation of organic compounds, including free radical halogenation, ketone halogenation, electrophilic halogenation, and halogen addition reaction. The structure of the substrate is one factor that determines the pathway.

Free radical halogenation

Saturated hydrocarbons typically do not add halogens but undergo free radical halogenation, involving substitution of hydrogen atoms by halogen. The regiochemistry of the halogenation of alkanes is usually determined by the relative weakness of the available C–H bonds. The preference for reaction at tertiary and secondary positions results from greater stability of the corresponding free radicals and the transition state leading to them. Free radical halogenation is used for the industrial production of chlorinated methanes:^[2]

CH₄ + Cl₂ → CH₃Cl + HCl

Rearrangement often accompany such free radical reactions.

Addition of halogens to alkenes and alkynes

Unsaturated compounds, especially alkenes and alkynes, add halogens:

RCH=CHR′ + X₂ → RCHX–CHXR′

The addition of halogens to alkenes proceeds via intermediate halonium ions. In special cases, such intermediates have been isolated.^[3]

Structure of a bromonium ion

Halogenation of aromatic compounds

Aromatic compounds are subject to electrophilic halogenation:^[4]

RC₆H₅ + X₂ → HX + RC₆H₄X

The facility of halogenation is influenced by the halogen. Fluorine and chlorine are more electrophilic and are more aggressive halogenating agents. Bromine is a weaker halogenating agent than both fluorine and chlorine, while iodine is least reactive of them all. The facility of hydrogenolysis follows the reverse trend: iodine is most easily removed from organic compounds and organofluorine compounds are highly stable.

Other halogenation methods

In the Hunsdiecker reaction, from carboxylic acids are converted to the chain-shortened halide. The carboxylic acid is first converted to its silver salt, which is then oxidized with halogen:

RCO₂Ag + Br₂ → RBr + CO₂ + AgBr

The Sandmeyer reaction is used to give aryl halides from diazonium salts, which are obtained from anilines.

In the Hell–Volhard–Zelinsky halogenation, carboxylic acids are alpha-halogenated.

In oxychlorination, the combination of hydrogen chloride and oxygen serves as the equivalent of chlorine, as illustrated by this route to dichloroethane:

2 HCl + CH₂=CH₂ + ¹⁄₂ O₂ → ClCH₂CH₂Cl + H₂O

Halogenation by halogen type

Fluorination

Organic compounds, saturated and unsaturated alike, react readily, usually explosively, with fluorine. Fluorination with elemental fluorine (F₂) requires highly specialized conditions and apparatus. Many commercially important organic compounds are fluorinated electrochemically using hydrogen fluoride as the source of fluorine. The method is called electrochemical fluorination. Aside from F₂ and its electrochemically generated equivalent, a variety of fluorinating reagents are known such as xenon difluoride and cobalt(III) fluoride.

Chlorination

Chlorination is generally highly exothermic. Both saturated and unsaturated compounds react directly with chlorine, the former usually requiring UV light to initiate homolysis of chlorine. Chlorination is conducted on a large scale industrially; major processes include routes to 1,2-dichloroethane (a precursor to PVC), as well as various chlorinated ethanes, as solvents.

Bromination

Bromination is more selective than chlorination because the reaction is less exothermic. Most commonly bromination is conducted by the addition of Br₂ to alkenes. An example of bromination is the organic synthesis of the anesthetic halothane from trichloroethylene:^[5]

Organobromine compounds are the most common organohalides in nature. Their formation is catalyzed by the enzyme bromoperoxidase which utilizes bromide in combination with oxygen as an oxidant. The oceans are estimated to release 1–2 million tons of bromoform and 56,000 tons of bromomethane annually.^[6]

Iodination

Iodine is the least reactive halogen and is reluctant to react with most organic compounds. The addition of iodine to alkenes is the basis of the analytical method called the iodine number, a measure of the degree of unsaturation for fats. The iodoform reaction involves degradation of methyl ketones.

Inorganic chemistry

All elements aside from argon, neon, and helium form fluorides by direct reaction with fluorine. Chlorine is slightly more selective, but still reacts with most metals and heavier nonmetals. Following the usual trend, bromine is less reactive and iodine least of all. Of the many reactions possible, illustrative is the formation of gold(III) chloride by the chlorination of gold. The chlorination of metals is usually not very important industrially since the chlorides are more easily made from the oxides and the hydrogen halide. Where chlorination of inorganic compounds is practiced on a relatively large scale is for the production of phosphorus trichloride and sulfur monochloride.^[7]

Chemical dehalogenation

Chemical dehalogenation is a treatment to remove halogens from harmful chemicals or contaminated areas by making them less toxic. There are two types of dehalogenation: glycolate dehalogenation and base-catalyzed decomposition.^[8]

References

^ Yoel Sasson "Formation of Carbon–Halogen Bonds (Cl, Br, I)" in Patai's Chemistry of Functional Groups, 2009, Wiley-VCH, Weinheim. doi:10.1002/9780470682531.pat0011
^ M. Rossberg et al. “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2
^ T. Mori; R. Rathore (1998). "X-Ray structure of bridged 2,2′-bi(adamant-2-ylidene) chloronium cation and comparison of its reactivity with a singly bonded chloroarenium cation". Chem. Commun. (8): 927–928. doi:10.1039/a709063c.
^ Illustrative procedure for chlorination of an aromatic compound: Edward R. Atkinson, Donald M. Murphy, and James E. Lufkin (1951). "dl-4,4′,6,6′-Tetrachlorodiphenic Acid". Org. Synth. ; Coll. Vol. 4, p. 872
^ Synthesis of essential drugs, Ruben Vardanyan, Victor Hruby; Elsevier 2005 ISBN 0-444-52166-6
^ Gordon W. Gribble “The diversity of naturally occurring organobromine compounds” Chemical Society Reviews, 1999, volume 28, pages 335–346.doi:10.1039/a900201d
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
^ A Citizen’s Guide to Chemical Dehalogenation by the U.S. EPA

English Journal

A high-throughput assay for arylamine halogenation based on a peroxidase-mediated quinone-amine coupling with applications in the screening of enzymatic halogenations.

Hosford J1, Shepherd SA, Micklefield J, Wong LS.
Chemistry (Weinheim an der Bergstrasse, Germany).Chemistry.2014 Dec 8;20(50):16759-63. doi: 10.1002/chem.201403953. Epub 2014 Oct 15.
Arylhalides are important building blocks in many fine chemicals, pharmaceuticals and agrochemicals, and there has been increasing interest in the development of more "green" halogenation methods based on enzyme catalysis. However, the screening and development of new enzymes for biohalogenation has
PMID 25319801

Oxidative halogenation of cisplatin and carboplatin: synthesis, spectroscopy, and crystal and molecular structures of Pt(iv) prodrugs.

Johnstone TC1, Alexander SM, Wilson JJ, Lippard SJ.
Dalton transactions (Cambridge, England : 2003).Dalton Trans.2014 Dec 2;44(1):119-29. doi: 10.1039/c4dt02627f.
A series of Pt(iv) prodrugs has been obtained by oxidative halogenation of either cisplatin or carboplatin. Iodobenzene dichloride is a general reagent that cleanly provides prodrugs bearing axial chlorides without the need to prepare intervening Pt(iv) intermediates or handle chlorine gas. Elementa
PMID 25367395

Biosynthesis of the halogenated mycotoxin aspirochlorine in koji mold involves a cryptic amino Acid conversion.

Chankhamjon P1, Boettger-Schmidt D, Scherlach K, Urbansky B, Lackner G, Kalb D, Dahse HM, Hoffmeister D, Hertweck C.
Angewandte Chemie (International ed. in English).Angew Chem Int Ed Engl.2014 Dec 1;53(49):13409-13. doi: 10.1002/anie.201407624. Epub 2014 Oct 10.
Aspirochlorine (1) is an epidithiodiketopiperazine (ETP) toxin produced from koji mold (Aspergillus oryzae), which has been used in the oriental cuisine for over two millennia. Considering its potential risk for food safety, we have elucidated the molecular basis of aspirochlorine biosynthesis. By a
PMID 25302411

Japanese Journal

ポリエチレングリコール添加による非プロトン性溶媒中へのナトリウム塩の溶解と,それを利用した有機化合物の効率的陽極酸化反応

SAWAMURA Takahiro,TAKAHASHI Kohta,INAGI Shinsuke [他],FUCHIGAMI Toshio
電気化学および工業物理化学 81(5), 365-367, 2013
… By using this method, anodic halogenation, anodic deprotection, and anodic coupling reaction of organic compounds were successfully carried out to provide desired products efficiently. …
NAID 130003376696

DIRECT HALOGENATION REACTIONS IN 2,3-DIHYDRO-4(1H)-QUINAZOLINONES

Cabrera-Rivera Fanny A.,Ortiz-Nava Claudia,Roman-Bravo Perla [他]
Heterocycles : an international journal for reviews and communications in heterocyclic chemistry 85(9), 2173-2195, 2012-09-01
NAID 40019392906

5-アルキルオキシメチル-8-キノリノール誘導体の銅(II)イオン抽出能に及ぼす7位ハロゲン化の効果

松田駿太朗,森田耕太郎,平山直紀 [他],井村久則
分析化学 = Japan analyst 61(8), 699-703, 2012-08-05
… From the distribution behavior of the reagents between carbon tetrachloride and water, an increase in hydrophobicity and acidity by the halogenation was confirmed. …
NAID 10030495326