Xylylene dibromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.001.857
EC Number
  • 202-042-7
UNII
  • InChI=1S/C8H8Br2/c9-5-7-3-1-2-4-8(7)6-10/h1-4H,5-6H2
    Key: KGKAYWMGPDWLQZ-UHFFFAOYSA-N
  • C1=CC=C(C(=C1)CBr)CBr
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:
GHS05: CorrosiveGHS07: Exclamation mark
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).
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]

References

  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)
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