Dichlorocarbon
| Structural formula | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||
| General | ||||||||||
| Surname | Dichlorocarbon | |||||||||
| other names |
|
|||||||||
| Molecular formula | CCl 2 | |||||||||
| External identifiers / databases | ||||||||||
|
||||||||||
| properties | ||||||||||
| Molar mass | 82.92 g mol −1 | |||||||||
| safety instructions | ||||||||||
|
||||||||||
| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||
Dichlorocbene is a carbene found in organic chemistry . The reactive intermediate with the empirical formula CCl 2 is easily accessible through the reaction between chloroform and a base dissolved in water such as potassium tert -butanolate or sodium hydroxide . The introduction of the bases present as salt into the organic chloroform phase must be carried out using a phase transfer catalyst .
presentation
Dichlorocarbene can also be obtained by reacting ethyl trichloroacetate with sodium methoxide in pentane or by thermal decomposition of phenyl (trichloromethyl) mercury.
Dichlorodiazirine is an experimental dichlorocarbene precursor that is stable in the dark at room temperature and provides the carbene compound by photolysis with the release of molecular nitrogen. Phenol reacts here with cyanogen bromide to phenyl cyanate (a) provided with hydroxylamine to N -hydroxy- O is reacted iminocarbamat -phenyl-(b). The hydroxy group is activated by methanesulfonyl chloride and converted into a mesyl group (c). The intramolecular ring closure to aziridine is achieved with sodium hypochlorite (d), followed by nitration of the phenyl group with nitronium tetrafluoroborate (e). In an ionic liquid , a nucleophilic substitution with cesium chloride is carried out under phase transfer catalysis with tetrabutylammonium chloride (f).
Dichlorocarbene can also be obtained by the sonochemical reaction of carbon tetrachloride with elemental magnesium . This reaction tolerates ester and carbonyl functions as no strong base is required.
Reactions
Dichlorocarbene reacts with alkenes formally in a [1 + 2] cycloaddition to form geminal dichlorocyclopropanes, which can then be reduced to the corresponding cyclopropanes or hydrolyzed with water to form a cyclopropanone . The preparation of dichlorocarbene from chloroform and its preparative use was discovered in 1954 by William von Eggers Doering , who functionalized cyclohexene in this way .
In the Reimer-Tiemann reaction , dichlorocarbene reacts with phenol to form salicylaldehyde .
history
Dichlorocarbene as a reactive intermediate was first proposed in 1862 by Anton Geuther , who interpreted chloroform as CCl 2 · HCl. In 1950 Jack Hine published an article on dichlorocarbene as a reaction intermediate in chloroform hydrolysis. The proof was provided by William von Eggers Doering in 1954.
Related reactions
In the allenes synthesis according to Doering-LaFlamme , alkenes are converted into allenes in a chain-lengthening reaction . For this purpose, the alkene is first made to react with dichlorocarbene in order to then obtain the allene through the use of magnesium or sodium. This reaction sequence also occurs in the production of cyclopentadienes by means of the Skattebøl rearrangement . The reaction between phenols with dichlorocarbene is known as the Reimer-Tiemann reaction. Closely related to dichlorocarbene is the more reactive dibromocarbene CBr 2 .
Chlorocarbene
The related chlorocarbene (ClHC) can be obtained by reacting dichlorocarbene with methyllithium . It can be used to obtain spiropentadiene .
Individual evidence
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ^ E. Vogel, W. Klug, A. Breuer: 1,6-Methanoannulene In: Organic Syntheses . 54, 1974, p. 11, doi : 10.15227 / orgsyn.054.0011 ; Coll. Vol. 6, 1988, p. 731 ( PDF ).
- ^ William E. Parham, Edward E. Schweizer, Sigmund A. Mierzwa Jr: 2-Oxa-7,7-Dichloronorcarane In: Organic Syntheses . 41, 1961, p. 76, doi : 10.15227 / orgsyn.041.0076 ; Coll. Vol. 5, 1973, p. 874 ( PDF ).
- ↑ Ted J. Logan: Phenyl (trichloromethyl) mercury In: Organic Syntheses . 46, 1966, p. 98, doi : 10.15227 / orgsyn.046.0098 ; Coll. Vol. 5, 1973, p. 969 ( PDF ).
- ↑ Haixia Lin, Yang Mingfa, Peigang Huang and Weiguo Cao: A Facile Procedure for the Generation of Dichlorocarbene from the reaction of carbon tetrachloride and magnesium using ultrasonic irradiation . In: Molecules 2003, 8, pp. 608–613 (PDF; 64 kB)
- ↑ The Addition of Dichlorocarbene to Olefins W. by E. Doering and A. Kentaro Hoffmann J. Am. Chem. Soc. ; 1954; 76 (23) pp. 6162-6165; doi : 10.1021 / ja01652a087
- ↑ About the decomposition of chloroform by alcoholic potassium solution Annalen der Chemie und Pharmacie Volume 123, Issue 1, Date: 1862, pp. 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
- ↑ W. von E. Doering and PM LaFlamme: A two-step of synthesis of allees from olefins . In: Tetrahedron , Volume 2, Issues 1-2, 1958, pp. 75-79 doi : 10.1016 / 0040-4020 (58) 88025-4 .