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1,2,4,5-Tetrabrombenzol Struktur.svg
3D model (JSmol)
ECHA InfoCard 100.010.231
EC Number 211-253-3
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Warning
H315, H319, H335, H413
P261, P264, P271, P273, P280, P302+352, P304+340, P305+351+338, P312, P321, P332+313, P337+313, P362, P403+233
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

1,2,4,5-Tetrabromobenzene is a fourfold symmetrically bromine-substituted benzene and starting material for liquid crystals and OLED materials, as well as for mono-[1] and bis-aryines.[2] 1,2,4,5-Tetrabromobenzene is an important metabolite of the completely brominated hexabromobenzene used as a flame retardant in the animal organism with liver-damaging properties.[3]


The synthesis of 1,2,4,5-tetrabromobenzene has already been reported in 1865 from benzene and excess bromine in a sealed tube at 150 °C.[4] However, the clearly reduced melting point of about 160 °C indicates impurities in the final product.

In 1885, Adolf Scheufelen published the synthesis of 1,2,4,5-tetrabromobenzene in the presence of ion(III) chloride FeCl3 as a catalyst in his dissertation and obtained a purer product (mp 175 °C) in "pretty needles" ("schönen Nadeln").[5]

Synthese von 1,2,4,5-Tetrabrombenzol

The synthesis can also be carried out in solution in chloroform or tetrachloromethane and yields 1,2,4,5-tetrabromobenzene in 89% yield.[6]

As a teaching example for electrophilic aromatic substitutions, this reaction can also be carried out in a laboratory experiment with excess bromine and iron nails (as starting material for iron (III) bromide FeBr3).[7] The intermediate stage is 1,4-dibromobenzene, which reacts further with excess bromine to give 1,2,4,5-tetrabromobenzene.


Building block for liquid crystals and fluorescent dyes[edit]

The symmetrical substitution pattern with reactive bromine atoms makes 1,2,4,5-tetrabromobenzene an interesting starting compound for nematic liquid crystals[8] with crossed mesogens

Synthese von gekreuzten nematischen LCs aus 1,2,4,5-Tetrabrombenzol

and for columnar (diskotic) liquid crystals[9][10] with an extensive planar, "board-like" tetrabenzoanthracene ring system.

Diskotische LC aus 1,2,4,5-Tetrabrombenzol

In a one-pot reaction, 1,2,4,5-tetrabromobenzene can be reacted with the aromatic aldehyde 4-hydroxybenzaldehyde, the alkylating agent 1-bromopentane, the Wittig reagent methyltriphenylphosphonium iodide, the base potassium carbonate, the phase transfer catalyst tetrabutylammonium bromide, the Heck reagent palladium(II)acetate and the Heck co-catalyst 1,3-bis(diphenylphosphino)propane (dppp) in dimethylacetamide obtaining directly a symmetrical tetraalkoxylstilbene as E-isomer in 17% yield.[11]

Synthese eines symmetrischer Tetraalkoxystilbens

Due to their pronounced π-conjugation such compounds could be potentially applied as optical brighteners, OLED materials or liquid crystals.

N-alkyl-tetraaminobenzenes are available from 1,2,4,5-tetrabromobenzene in high yields, which can be cyclized with triethyl orthoformate and acids to benzobis(imidazolium) salts (BBI salts) and oxidized with oxygen to form 1,4-benzoquinone diimines.[12]

Synthese von BBI-Salzen und Benzochinondiiminen

BBI salts are versatile fluorescent dyes with emission wavelengths λem between 329 and 561 nm, pronounced solvatochromism and strong solvent-dependent Stokes shift, which can be used as protein tag for fluorescent labeling of proteins.[13]

Starting material for arines[edit]

From 1,2,4,5-tetrabromobenzene, an 1,4-monoarine can be prepared in-situ with one equivalent of n-butyllithium by bromine abstraction, which reacts immediately with furan to form 6,7-dibromo-1,4-epoxy-1,4-dihydronaphthalene (6,7-dibromonaphthalene-1,4-endoxide) in 70% yield.[1]

Bildung eines 1,4-Monoarins aus 1,2,4,5-Tetrabrombenzol

When 2,5-dialkylfurans (e.g. 2,5- (di-n-octyl)furan) are used, the dibrominated monoendoxide is formed in 64% yield, from which dibromo-5,8-di-n-octylnaphthalene is formed with zink powder/titanium tetrachloride in 88% yield.[14]

Synthese von Dibromdioctylnaphthalin aus 1,2,4,5-Tetrabrombenzol

With titanium tetrachloride/zinc powder, the endoxide can be reduced to the 2,3-dibromnaphthalene in 86% yield.[15]

Bildung von 2,3-Dibromnaphthalin aus 1,2,4,5-Tetrabrombenzol

The endoxide reacts with 3-sulfolene in a Diels-Alder reaction upon elimination of sulfur dioxide to form a tricyclic adduct, from which 2,3-dibromoanthracene is accessible in good yield.[16]

If the dibromene oxide is allowed to react further with furan, in the presence of n-butyllithium[1] or potassium amide[17] or via an intermediate 1,4-aryne the tricyclic 1,4-adduct 1,4:5.8-diepoxy-1,4,5,8-tetrahydroanthracene[18] is formed in 71% yield as a syn-anti-mixture.

Bildung eines 1,4-Bisarins mit Furan

With sodium amide in ethylene glycol dimethyl ether (DME), however, the dibromene oxide behaves as a 1,3-aryene equivalent and forms with furan a phenanthrene-like tricyclic 1,3-adduct, which can react with furan and sodium amide to a triphenylene derivative (1,3,5-tris-arene).[17]

Triphenylenderivat über 1,3,5-tris-Arin

[2+4] cycloadditions with 1,2,4,5-tetrabromobenzene sometimes proceed in very high yields, such as the reaction of a dihalogen-substituted 1,3-diphenyl-isobenzofuran to a tetrahalogenated anthracene derivative (98%), which is converted successively further with 1,3-diphenyl isobenzofuran in 65% yield to a pentacene derivative and furan to a hexacene derivative (67%).[19]

Bildung eines Hexacen-Derivats aus 1,2,4,5-Tetrabrombenzol

The crosslinking of benzimidazole-modified polymers provides materials with a high absorption capacity for carbon dioxide, which could be suitable for CO2 separation from gas mixtures.[20]

Bildung eines vernetzten Benzimidazolpolymers


1,2,4,5-Tetrabromobenzene is a liver toxic degradation product of the flame retardant hexabromobenzene and was already in 1987 detected in Japan in mother's milk samples.[21]


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