Durene, bromination

Durene, pentamethyl benzene and hexamethyl benzene have usually been prepared from benzene or one of its methylated derivatives by the Friedel-Crafts synthesis.1 Durene has been made from bromine derivatives of methylated benzenes by the Fittig reaction.2 It has also been obtained in 20 per cent yield by passing methyl alcohol and acetone vapors over heated alu-... 

Periodic acid dihydrate, with iodine and durene to give iododurene, 51, 94 Phenols, from aryl methyl ethers, 53, 93 Phenylacetaldehyde, from 2-lithio-1,3,5-trithiane and benzyl bromide, 51, 43 Phenylacetic acid, bromination, 50, 31... 

Is it possible that the unexpectedly slow oxidations of molecules such as mesitylene, durene, and the methylnaphthalenes which the author has described are caused by the depletion of the bromide portion of the catalyst In these cases, bromination of the activated nuclei could occur and the bromide would be lost permanently. 

In contrast to chlorine, bromine, and iodine, which deactivate aromatic rings for electrophilic substitutions, fluorine exerts an even higher activation of the ring than does hydrogen, as has been shown by measurements of the rates of bromination of durene (1,2,4,5-tetramethylben-zene) and its 3-halo derivatives [35]. 

An ab initio MO study of the mechanism of chlorination of benzene by chlorine in the presence of aluminium chloride has appeared. The rate-limiting stage leads to the formation of the ion-pair complex CeHeCl AlCU" without the explicit formation of Cl, the formation of C-Cl and Al-Cl bonds occurring synchronously with the breaking of the Cl-Cl bond. The introduction of a 3-chloro substituent into benzoyl chloride deactivates the system to further chlorination at the 5-position by a factor of about 6. ° Benzene, toluene, the xylenes, durene, mesitylene, nitrobenzene, and p-nitrotoluene are selectively brominated at 50-65 °C in an HBr-HN03-H2S04-H20 mixture with the participation of oxygen. The small catalytic amount of nitric acid oxidizes HBr to Br+, which reacts with the aromatic compound, and the nitrous acid formed reacts... 

Aromatic compounds are conveniently chlorinated or brominated in the laboratory. For example, durene is chlorinated at 0 C in chloroform to 57% monochlorodurene (mp 47°-48 C). In the absence of catalysts and in sunlight, alkylbenzenes are brominated or chlorinated in the side chain. 

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