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Dibromocarbene

Dichlorocarbene
Wireframe model of dichlorocarbene
Ball and stick model of dichlorocarbene
Names
Preferred IUPAC name
Dichlorocarbene
Systematic IUPAC name
Dichloromethylidene
Other names
Carbon(II) chloride

Carbon dichloride
Carbonous chloride
Dichloro-λ2-methane

Dichloromethylene
Identifiers
3D model (JSmol)
1616279
ChEBI
ChemSpider
200357
MeSH Dichlorocarbene
PubChem CID
Properties
CCl2
Molar mass 82.91 g·mol−1
Hazards
Main hazards Highly reactive
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Carbon dichloride
Carbonous chloride
Dichloro-λ2-methane

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.

Another precursor to dichlorocarbene is ethyl trichloracetate. Upon treated with sodium methoxide, it releases CCl2. Phenyl(trichloromethyl)mercury decomposes thermally to also release CCl2:

Dichlorodiazirine, which is stable in the dark, decomposes into dichlorocarbene and nitrogen via photolysis.

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 geminal halide hydrolysis. Dichlorocyclopropanes may also be converted to allenes in the Skattebøl rearrangement.


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