Xylylene dibromide

Xylylene dibromide
Identifiers
CAS Number	91-13-4 ;
3D model (JSmol)	Interactive image;
ChemSpider	60032;
ECHA InfoCard	100.001.857
EC Number	202-042-7;
PubChem CID	66665;
UNII	9FRJ55E5UL;
CompTox Dashboard (EPA)	DTXSID2059019 ;
	InChI InChI=1S/C8H8Br2/c9-5-7-3-1-2-4-8(7)6-10/h1-4H,5-6H2 Key: KGKAYWMGPDWLQZ-UHFFFAOYSA-N;
	SMILES C1=CC=C(C(=C1)CBr)CBr;
Properties
Chemical formula	C8H8Br2
Molar mass	263.960 g·mol−1
Appearance	off-white solid
Melting point	93–94 °C (199–201 °F; 366–367 K)
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	lachrymator
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H314
Precautionary statements	P260, P264, P270, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P330, P363, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Xylylene dibromide is an organic compound with the formula C₆H₄(CH₂Br)₂. It is an off-white solid that, like other benzyl halides, a strong lachrymator. It is a useful reagent owing to the convenient reactivity of the two C-Br bonds.[1] Two other isomers are known, para- and meta-xylylene dibromide.

Synthesis

It is prepared by the photochemical reaction of ortho-xylene with bromine:[2]

C₆H₄(CH₃)₂ + 2 Br₂ → C₆H₄(CH₂Br)₂ + 2 HBr

Reactions

Further bromination gives the tetrabromide:[3]

C₆H₄(CH₂Br)₂ + 2 Br₂ → C₆H₄(CHBr₂)₂ + 2 HBr

Upon reaction with thiourea followed by hydrolysis of the intermediate bisisothiouronium salts, xylylene dibromide can be converted to the dithiol C₆H₄(CH₂SH)₂.[4]

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.[5]

Coupling of xylylene dibromide by treatment with lithium metal gives dibenzocyclooctane, precursor to dibenzocyclooctadiene.[6]

Related compounds

Xylylene dichloride, the dichloro analogue of the title compound.
Benzyl bromide, the simplest benzylic bromide.

References

Bornstein, J.; Shields, J. E. (1967). "2-(p-Tolylsulfonyl)dihydroisoindole". Organic Syntheses. 47: 110. doi:10.15227/orgsyn.047.0110.
Emily F. M. Stephenson (1954). "o-Xylylene Dibromide". Organic Syntheses. 34: 100. doi:10.15227/orgsyn.034.0100.
Bill, J. C.; Tarbell, D. S. (1954). "o-Phthalaldehyde". Organic Syntheses. 34: 82. doi:10.15227/orgsyn.034.0082.
Mayerle, J. J.; Denmark, S. E.; Depamphilis, B. V.; Ibers, James A.; Holm, R. H. (1975). "Synthetic Analogs of the Active Sites of Iron-Sulfur Proteins. XI. Synthesis and Properties of Complexes Containing the Iron Sulfide (Fe₂S₂) Core and the Structures of Bis[o-Xylyl-α,α'-Dithiolato-μ-Sulfido-Ferrate(III)] and bis[p-Tolylthiolato-μ-Sulfido-Ferrate(III)] Dianions". Journal of the American Chemical Society. 97 (5): 1032–1045. doi:10.1021/ja00838a015.
Kerber, Robert C.; Ribakove, Everett C. (1991). "Formation of Iron Carbonyl Complexes of Reactive Polyenes from Dihalides involving the Free Polyene". Organometallics. 10 (8): 2848–2853. doi:10.1021/om00054a059.
Géraldine Franck, Marcel Brill, Günter Helmchen (2012). "Dibenzo[a,e]cyclooctene: Multi-gram Synthesis of a Bidentate Ligand". Organic Syntheses. 89: 55. doi:10.15227/orgsyn.089.0055.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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[1] Bornstein, J.; Shields, J. E. (1967). "2-(p-Tolylsulfonyl)dihydroisoindole". Organic Syntheses. 47: 110. doi:10.15227/orgsyn.047.0110.

[2] Emily F. M. Stephenson (1954). "o-Xylylene Dibromide". Organic Syntheses. 34: 100. doi:10.15227/orgsyn.034.0100.

[3] Bill, J. C.; Tarbell, D. S. (1954). "o-Phthalaldehyde". Organic Syntheses. 34: 82. doi:10.15227/orgsyn.034.0082.

[4] Mayerle, J. J.; Denmark, S. E.; Depamphilis, B. V.; Ibers, James A.; Holm, R. H. (1975). "Synthetic Analogs of the Active Sites of Iron-Sulfur Proteins. XI. Synthesis and Properties of Complexes Containing the Iron Sulfide (Fe₂S₂) Core and the Structures of Bis[o-Xylyl-α,α'-Dithiolato-μ-Sulfido-Ferrate(III)] and bis[p-Tolylthiolato-μ-Sulfido-Ferrate(III)] Dianions". Journal of the American Chemical Society. 97 (5): 1032–1045. doi:10.1021/ja00838a015.

[5] Kerber, Robert C.; Ribakove, Everett C. (1991). "Formation of Iron Carbonyl Complexes of Reactive Polyenes from Dihalides involving the Free Polyene". Organometallics. 10 (8): 2848–2853. doi:10.1021/om00054a059.

[6] Géraldine Franck, Marcel Brill, Günter Helmchen (2012). "Dibenzo[a,e]cyclooctene: Multi-gram Synthesis of a Bidentate Ligand". Organic Syntheses. 89: 55. doi:10.15227/orgsyn.089.0055.{{cite journal}}: CS1 maint: multiple names: authors list (link)