Chlorination

The title of this article is ambiguous. For chlorination in metallurgy, see Chlorination (Metallurgy) . For information on chlorination in the disinfection of food, see chlorination .

Chlorination - also chlorination - is a form of halogenation in chemistry . The element chlorine is introduced into an organic chemical compound . Inorganic or low molecular weight organic chlorinating agents are used to introduce chlorine into a chemical compound . Of the chlorinating agents, molecular chlorine is the most widely used. Depending on the process, a distinction is made between thermal, catalytic or photochemical chlorination .

Chlorination reactions

The introduction of chlorine takes place via addition or substitution reactions . The presence of typical halogen carriers such as iron or iodine often promotes chlorination. Photochlorination is of technical importance. An alkane is converted into chloroalkanes in a radical reaction .

Addition reactions

Monochlorinated alkanes are obtained by the addition reaction of hydrogen chloride (HCl) with alkenes. Similarly, from cyclohexene, by addition of hydrogen chloride to the C = C double bond, chlorocyclohexane is formed :

1,2-Dichlorinated alkanes are formed by the addition of chlorine (Cl ₂ ) to alkenes, e.g. B. Cyclohexene;

Analogously, the addition of chlorine (Cl ₂ ) to alkynes initially gives trans -1,2-dichlorinated alkenes. The addition of another chlorine molecule results in 1,1,2,2-tetrachloroalkanes.

Substitution reactions

The photochlorination of methane gives monochloromethane , dichloromethane (methylene chloride), trichloromethane (chloroform) and carbon tetrachloride as a mixture of chlorination products ; Schematic representation without taking stoichiometry into account :

Alkylated aromatics (e.g. toluene ) can be specifically chlorinated in the side chain ( SSS rule ) or on the aromatic core ( KKK rule ). - In the allyl position, alkenes can be chlorinated with N -chlorosuccinimide. The action of phosphorus chlorides or thionyl chloride on alcohols can be used to produce chloroalkanes, the hydroxyl group being substituted by a chlorine atom.

Chlorinating agents

Inorganic chlorinating agents (selection)

• chlorine
• Hydrogen chloride
• Antimony pentachloride
• Hypochlorous acid
• Phosphorus oxychloride
• Phosphorus pentachloride
• Phosphorus trichloride
• Sulfuryl chloride
• Thionyl chloride
• Chloramines

Organic chlorinating agents (selection)

• N -chlorosuccinimide
• Carbon tetrachloride
• Carboxylic acid chlorides

Individual evidence

1. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 1: A-Cl. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1979, ISBN 3-440-04511-0 , pp. 720-721, 732-733.
2. ↑ Hans Peter Latscha, Uli Kazmaier, Helmut Alfons Klein: Organic Chemistry: Chemistry Basics II . Springer DE, 2008, ISBN 3-540-77107-7 , pp. 56 ( limited preview in Google Book search).
3. ^ Siegfried Hauptmann : Organic chemistry. 2nd reviewed edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, p. 260, ISBN 3-342-00280-8 .
4. ↑ Ulrich Lüning: Organic reactions. 2nd edition, Elsevier GmbH, Munich, 2007, p. 89, ISBN 978-3-8274-1834-0 .
5. ^ ^{A b} Siegfried Hauptmann: Organic chemistry. 2nd reviewed edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, p. 297, ISBN 3-342-00280-8 .