|Jmol-3D images||Image 1|
|Molar mass||82.92 g mol−1|
|Main hazards||Highly reactive|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
Dichlorocarbene is the reactive intermediate with chemical formula CCl2. Although this material has not been isolated, it is a common intermediate in organic chemistry, being generated from chloroform. This bent diamagnetic molecule rapidly inserts into other bonds.
Dichlorocarbene is most commonly generated by reaction of chloroform and a base such as potassium t-butoxide or aqueous sodium hydroxide. A phase transfer catalyst, for instance benzyltriethylammonium bromide, facilitates the migration of the hydroxide in the organic phase.
- HCCl3 + NaOH → CCl2 + NaCl + H2O
Other reagents and routes
- PhHgCCl3 → CCl2 + PhHgCl
|Dichlorocarbene from dichlorodiazirine |
Dichlorocarbene can also be obtained by dechlorination of carbon tetrachloride with magnesium with ultrasound chemistry. This method is tolerant to esters and carbonyl compounds because it does not involve strong base.
Dichlorocarbene reacts with alkenes in a formal [1+2]cycloaddition to form geminal dichlorocyclopropanes. These can be reduced to cyclopropanes or hydrolysed to give cyclopropanones by a gem halide hydrolysis. Dichlorocyclopropanes may also be converted to allenes in the Skattebøl rearrangement.
Dichlorocarbene as a reactive intermediate was first proposed by Anton Geuther in 1862 who viewed chloroform as CCl2.HCl Its generation was reinvestigated by Hine in 1950. The preparation of dichlorocarbene from chloroform and its utility in synthesis was reported by William von Eggers Doering in 1954.
The Doering–LaFlamme carbon chain extension entails the conversion of alkenes to allenes (a chain extension) with magnesium or sodium metal through initial reaction of the alkene with dichlorocarbene. The same sequence is incorporated in the Skattebøl rearrangement to cyclopentadienes. Dichlorocarbene also features in the Reimer–Tiemann reaction. Closely related is the more reactive dibromocarbene CBr2.
-  English translation of 1969 Polish patent on preparation of dichloropropane derivatives
- Organic Syntheses, Coll. Vol. 5, p.874 (1973); Vol. 41, p.76 (1961).
- Organic Syntheses, , Coll. Vol. 6, p.731 (1988); Vol. 54, p.11 (1974).Online Article
- Organic Syntheses, , Coll. Vol. 5, p.969 (1973); Vol. 46, p.98 (1966).
- Dichlorodiazirine: A Nitrogenous Precursor for Dichlorocarbene Gaosheng Chu, Robert A. Moss, and Ronald R. Sauers J. Am. Chem. Soc., 127 (41), 14206 -14207, 2005 doi:10.1021/ja055656c
- a) Starting from phenol reaction with cyanogen bromide to phenyl cyanate b) hydroxylamine reaction to the N-hydroxy-O-phenylisourea c) elevate hydroxyl group to leaving group by reaction with mesyl chloride to the mesylate d) intramolecular ring closure with sodium hypochlorite to the diazirine e) nitration with nitronium tetrafluoroborate f) nucleophilic substitution with caesium chloride, tetrabutylammonium chloride in ionic liquid
- A Facile Procedure for the Generation of Dichlorocarbene from the Reaction of Carbon Tetrachloride and Magnesium using Ultrasonic Irradiation Haixia Lin, Mingfa Yang, Peigang Huang and Weiguo Cao Molecules 2003, 8, 608-613 Online Article
- Wynberg, Hans (1960). "The Reimer-Tiemann Reaction". Chemical Reviews 60 (2): 169–184. doi:10.1021/cr60204a003. Retrieved 3 January 2014.
- Ueber die Zersetzung des Chloroforms durch alkoholische Kalilösung Annalen der Chemie und Pharmacie Volume 123, Issue 1, Date: 1862, Pages: 121-122 A. Geuther doi:10.1002/jlac.18621230109
- Carbon Dichloride as an Intermediate in the Basic Hydrolysis of Chloroform. A Mechanism for Substitution Reactions at a Saturated Carbon Atom Jack Hine J. Am. Chem. Soc., 1950, 72 (6), pp 2438–2445 doi:10.1021/ja01162a024
- The Addition of Dichlorocarbene to Olefins W. von E. Doering and A. Kentaro Hoffmann J. Am. Chem. Soc.; 1954; 76(23) pp 6162 - 6165; doi:10.1021/ja01652a087
- A two-step of synthesis of allenes from olefins Tetrahedron, Volume 2, Issues 1-2, 1958, Pages 75-79 W. von E. Doering and P. M. LaFlamme doi:10.1016/0040-4020(58)88025-4