Methylbenzenes, side-chain

Arstad BR, Nicholas JB, Haw JF. Theoretical study of the methylbenzene side-chain hydrocarbon pool mechanism in methanol to olefin catalysis. J Am Chem Soc 2004 126 2991-3001. 

Lesthaeghe D, Horre A, Waroquier M, Marin GB, Van Speybroeck V. Theoretical insights on methylbenzene side-chain growth in ZSM-5 zeolites for methanol-to-olefin conversion. Chem Eur J 2009 15 10803-8. 

Side chain oxidation of methylbenzenes has been developed into a route for the... 

There is increasing interest in studying the alkylation of methylbenzenes in the side chain with methyl alcohol over zeolite catalysts.270 These reactions may lead to new nontraditional technologies in the synthesis of styrene from toluene and that of p-methy I styrene from p-xylene. A one-step route from toluene or p-xylene to the corresponding styrenes would be of great practical importance compared with the presently practiced two-step syntheses (alkylation followed by dehydrogenation). 

C120 is a most potent chlorinating agent in radical side-chain chlorination of deactivated methylbenzenes and also in the electrophilic substitution of aromatics bearing electron-withdrawing groups819. 

When considering the rate constants for deprotonation reported in Table 2 one should, however, take into account that in methylbenzene radical cations with < 3 methyl groups, nucleophilic attack of water on the aromatic ring can compete efficiently with side-chain deprotonation. An elegant explanation which accounts for this competition has been provided for the toluene radical cation on the basis of the three-electron three-orbital three-configuration approach [135, 136]. Three electrons are involved in the deprotonation reaction—the unpaired electron delocalized over... 

In the case of methylbenzenes, oxidation of the side chain can be interrupted by trapping the aldehyde in the form of a non-oxidizable derivative, the gem-diacetate (Latin Gemini, twins), which is isolated and then hydrolyzed. 

The alkylbenzenes (single-ring aromatic compounds with single or multiple aliphatic side chains) are constituents of JP-8. Toluene (methylbenzene) and mixed xylenes (o-, m-, andp-) are present in JP-8 and have been identified as potential neurotoxic chemicals after sufficiently high intentional, accidental, or occupational exposures (Gamberale and Hultengren 1972 Boor and Hurtig 1977 Klaucke et al. 1982 Hipolito 1980). 

Higher plant resorcinolic lipids include very simple homologues of the orcino 1-type (l,3-dihydroxy-5-methylbenzene) phenols and a variety of homologues that are derivatives with the ring, chain or both ring and chain modified. Resorcinolic lipid molecules have a dual, aromatic and acyclic character. In most cases the side chain in resorcinolic lipids is odd numbered, which is relevant with regard to their possible biosynthetic pathway. 

Cobalt(III) acetate oxidizes thianthrene and 9,10-diphenyl-anthracene in acetic or trifluoroacetic acid to the cation radicals, as shown by esr (Heiba et al., 1969b). In flow systems, Co(III) acetate in trifluoroacetic acid has also given well-resolved esr spectra of polyalkylbenzene cation radicals (hexa-, penta-, and all tetra-methylbenzenes, 1,3,5-tri-t-butyl-, and 1,4-di-t-butylbenzene) which are difficult to make in other ways (Dessau et al., 1970). When similar oxidations of alkylaromatics are carried out in static systems, further reactions occur, and these are sometimes of preparative value, since among the products are nuclear and side chain acetates. The reactions have been clarified most recently by the work of Heiba and Dessau. 

The simplest of the alkylbenzenes (compounds made up of aromatic and alkane units), methylbenzene, is given the name of toluene. Compounds with longer side chains are named by prefixing the ncime of the alkyl group to the word... 

Benzylic chlorination of methylbenzene takes place in the gas phase at 400-600 °C or in the presence of UV light. When an excess of chlorine is used, multiple chlorinations of the side chain occur ... 

CD and VPO studies reveal that acychc alkyne pentamer (P)-7S (Fig. 22) bearing perfluorooctyl side chains forms a homo-double-helix structure in trilluor-omethylbenzene, a strong helix-forming solvent [72]. Unlike in chloroform, pentamer P)-ll (n = 5) also forms a homo-double-helix structure in trifluoro-methylbenzene. Interestingly, the mixture of (F)-pentamer 78 and (M)-pentamer of 77 n = 5) produces a hetero-double-helix dimer, indicating its higher stability over the homo-double-helix dimers of (F)-78 and (M)-77 n = 5). On the other hand, the... 

Some interesting examples of C-H activation by proximity have been reported in the reaction of [Pt(PPh3)2Cl2] with l,3-bis(diphenylphosphino)methylbenzenes. The 2- position becomes bound to platinum. A variety of complexes were prepared and their chemistry investigated. Utilisation of chirality at the a carbon atom of the side-chains was also explored. A subsequent paper by the... 

Notice that the methyl side-chain is not affected under the conditions used in the reaction above. However, we learnt on page 206 that chlorine will react with alkanes in the presence of ultraviolet (UV) light or strong sunlight. This is a free radical substitution reaction. So if the chlorine gas is passed into boiling methylbenzene, in the presence of UV light, the following reaction takes place ... 

Sometimes the presence of the benzene ring affects the usual reactions of its side-chain, e.g. methylbenzene is oxidised by refluxing with alkaline potassium manganate(Vll) to form benzoic acid. 

Masnovi, J.M., Sankararaman, S., and Kochi, J.K., Direct observation of the kinetic acidities of transient aromatic cation radicals. The mechanism of electrophilic side-chain nitration of methylbenzenes,/. Am. Chem. Soc., Ill, 2263, 1989. 

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