Xylylene dibromide is an
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
with the formula C
6H
4(CH
2Br)
2. It is an off-white solid that, like other
benzyl halides, a strong
lachrymator
Tear gas, also known as a lachrymator agent or lachrymator (), sometimes colloquially known as "mace" after the early commercial aerosol, is a chemical weapon that stimulates the nerves of the lacrimal gland in the eye to produce tears. In ad ...
. It is a useful reagent owing to the convenient reactivity of the two C-Br bonds. Two other isomers are known, para- and meta-xylylene dibromide.
Synthesis
It is prepared by the
photochemical reaction Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ...
of
ortho-xylene with
bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...
:
:C
6H
4(CH
3)
2 + 2Br
2 → C
6H
4(CH
2Br)
2 + 2 HBr
Reactions
Further bromination gives the tetrabromide:
:C
6H
4(CH
2Br)
2 + 2Br
2 → C
6H
4(CHBr
2)
2 + 2 HBr
Upon reaction with
thiourea
Thiourea () is an organosulfur compound with the formula and the structure . It is structurally similar to urea (), except that the oxygen atom is replaced by a sulfur atom (as implied by the ''thio-'' prefix); however, the properties of urea ...
followed by hydrolysis of the intermediate bis
isothiouronium
In organic chemistry, isothiouronium is a functional group with the formula SC(NH2)2sup>+ (R = alkyl, aryl) and is the acid salt of isothiourea. The H centres can also be replaced by alkyl and aryl. Structurally, these cations resemble guanid ...
salts, xylylene dibromide can be converted to the
dithiol
In organic chemistry, a dithiol is a type of organosulfur compound with two thiol () functional groups. Their properties are generally similar to those of monothiols in terms of solubility, odor, and volatility. They can be classified according ...
C
6H
4(CH
2SH)
2.
Xylylene dibromide is a precursor to the ephemeral molecule ortho-quinonedimethane, also known as
xylylene. This species can be trapped when the dehalogenation is conducted in the presence of
iron carbonyl
Iron pentacarbonyl, also known as iron carbonyl, is the compound with formula . Under standard conditions Fe( CO)5 is a free-flowing, straw-colored liquid with a pungent odour. Older samples appear darker. This compound is a common precursor to ...
.
Coupling of xylylene dibromide by treatment with lithium metal gives dibenzocyclooctane, precursor to dibenzocyclooctadiene.
[{{cite journal , doi=10.15227/orgsyn.089.0055, title=Dibenzo[a,e]cyclooctene: Multi-gram Synthesis of a Bidentate Ligand , journal=Organic Syntheses , year=2012 , volume=89 , page=55, author=Géraldine Franck, Marcel Brill, Günter Helmchen ]
Related compounds
*
Xylylene dichloride, the dichloro analogue of the title compound.
*
Benzyl bromide
Benzyl bromide is an organic compound with the formula . The molecule consists of a benzene ring substituted with a bromomethyl group. It is a colorless liquid with lachrymatory properties. The compound is a reagent for introducing benzyl groups ...
, the simplest benzylic bromide.
References
Organobromides
Benzyl compounds
Lachrymatory agents