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.
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.001.857 |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| 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
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lachrymator |
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| Danger | |
| H302, H314 | |
| 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).
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Synthesis
editIt is prepared by the photochemical reaction of ortho-xylene with bromine:[2]
- C6H4(CH3)2 + 2 Br2 → C6H4(CH2Br)2 + 2 HBr
Reactions
editFurther 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
edit- Xylylene dichloride, the dichloro analogue of the title compound.
- Benzyl bromide, the simplest benzylic bromide.
References
edit- ^ 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.
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