Xylylene dibromide is an
organic compound
Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
with the formula C
6H
4(CH
2Br)
2. It is an off-white solid that, like other
benzyl halides, is strongly
lachrymator
Tear gas, also known as a lachrymatory agent or lachrymator (), sometimes colloquially known as "mace" after the Mace (spray), early commercial self-defense spray, is a chemical weapon that stimulates the nerves of the lacrimal gland in the ey ...
y. 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
''o''-Xylene (''ortho''-xylene) is an aromatic hydrocarbon with the formula C6H4(CH3)2, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of ''m''-xylene and ...
with
bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
:
: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 (), with the oxygen atom replaced by sulfur atom (as implied by the '' thio-'' prefix). The properties of urea and thiourea differ s ...
followed by hydrolysis of the intermediate bis
isothiouronium
In organic chemistry, isothiouronium is a functional group with the formula SC(NH2)2
SC, Sc or sc may refer to:
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* ''Soulcalibur ...
(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 guanidiniu ...
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
In organic chemistry, a xylylene (sometimes quinone-dimethide) is any of the constitutional isomers having the formula C6H4(CH2)2. These compounds are related to the corresponding quinones and quinone methides by replacement of the oxygen atoms ...
. This species can be trapped when the dehalogenation is conducted in the presence of
iron carbonyl There are three homoleptic iron carbonyl compounds:
* The monomeric iron pentacarbonyl
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 wit ...
.
Coupling of xylylene dibromide by treatment with lithium metal gives dibenzocyclooctane, precursor to
dibenzocyclooctatetraene.
[{{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 , doi-access=free ]
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 group ...
, the simplest benzylic bromide.
References
Organobromides
Benzyl compounds
Lachrymatory agents