Xylylene dibromide
Chemical compound
From Wikipedia, the free encyclopedia
Xylylene dibromide is an organic compound with the formula C6H4(CH2Br)2. It is an off-white solid that, like other benzyl halides, is strongly lachrymatory. 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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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 |
lachrymator |
| GHS labelling: | |
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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
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 dibenzocyclooctatetraene.[6]
Related compounds
- Xylylene dichloride, the dichloro analogue of the title compound.
- Benzyl bromide, the simplest benzylic bromide.