Pentamethyl benzene

Finally, the brominations of mesitylene, 1,2,4,5-tetramethyl- and pentamethyl-benzene in chloroform (which is more polar than carbon tetrachloride) are first-order in bromine and iodine monobromide318, so that this is entirely consistent with the pattern developed above, i.e. the more polar the solvent and the more reactive the compound, the fewer the number of molecules of iodine monobromide that are involved in the rate-determining step. Measurements of rates between 25 and 42 °C revealed no significant trend owing to the variability of the rate coefficients determined at any temperature, but even so it is clear that there is no appreciable activation energy for these compounds, and there may have been temperature inversion for some of them. 

Pentamethyl benzene.—Fraction V, and xylene which is methylated beyond the tetramethyl benzene stage, may be worked up for pentamethyl benzene. If xylene is to be methylated to obtain pentamethyl benzene, one more mole of methyl chloride should be used, and the mixture of xylene and anhydrous aluminium chloride methylated for one hundred and ten hours instead of the one hundred used for durene. Otherwise the procedure is exactly the same as for durene. The reaction mixture is decomposed and fractionated in the usual way, and the material boiling above 205° (fraction V) is separated into three frac-... 

Tetra- and pentamethyl benzene Mostly pentamethyl benzene Ilcxamcthyl benzene and tars... 

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-... 

The pentamethyl benzene obtained in this way is nearly pure, and one recrystallization from 95 per cent alcohol or from a mixture of equal volumes of alcohol and benzene gives a snow-white product, but the product generally melts over too wide a range for practical purposes. However, if fraction VII is refractionated under diminished pressure and the fraction boiling at i23-i33°/22 mm. (practically all at 127-1290) is collected and recrystallized as in the following paragraph, a product melting quite sharply at 52° (true m.p. 530) is obtained. 

Six hundred grams of crude pentamethyl benzene is heated to ioo° and poured slowly with stirring into 1000 cc. of 95 per cent ethyl alcohol heated to 70° in a 2-1. beaker, and allowed to stand over night at a temperature of approximately 30°. The crystals formed are collected on a suction filter and dried at room temperature over night on a porous plate. The yield is about 25° g. (Note 9). 

The method for the production of large amounts of hexamethyl benzene is the rapid methylation of pentamethyl benzene or the durene filtrates. A mixture of 378 g. of pentamethyl benzene and 200 g. of anhydrous aluminium chloride is heated... 

The melting point of pentamethyl benzene is only slightly affected by recrystallization, because most of the impurity is hexamethyl benzene, which can be removed only by fractionation. 

Fig. 12. Electron excitation spectra (a) of mesitylene in n-heptane, (b) of its proton addition complex in HF + BFs, and (c) of the proton addition complex of pentamethyl-benzene in HF. (DaUinga et al., 1968a Brouwer et cU., 1966sk)...

In the case of isodurene, the values scatter badly, as was to be expected from the equivalent conductances above 0-1 molal in Table 11. It is, however, interesting to note that the straight lines for pentamethyl-benzene and mesitylene intersect very nearly on the abscissa. This means that the values of these aromatic substances are the same and that the assumption of Kilpatrick and Luborsky (1953) is supported by... 

Property 1,3,5-Trimethyl- benzene 1,2,4- Trimethyl- benzene 1.2.3- Trimethyl- benzene 1,2,4,5-Te tram ethylbenzene 1,2,3,5-Tfetramethyl-benzene 1,2,3,4-Tetramethyl-benzene Pentamethyl- benzene Hexamethyl- benzene... 

C11H1402 alpha-isopropylbenzeneacetic acid 3508-94-9 22.09 1.0291 2 22354 C11H16 pentamethyl benzene 700-12-9 54.30 0.9789 1... 

C11H16 pentamethyl benzene 700-12-9 in benzene 0.069 1 25738 C13H12 diphenylmethane 101-81-5 in benzene 0.770 1... 

These acylium ions react rapidly with aromatic hydrocarbons such as pentamethyl-benzene to give the Friedel-Crafts acylation products. Thus, the mechanisms consists of formation of the complex, ionization to an acylium ion, and substitution via a cyclohexadienylium ion intermediate. The most likely mechanism for formation of the acylium ion is by an intramolecular transfer of the halide to the Lewis acid. 

Other Friedel-Crafts type catalysts can also be used, but boron trifluoride is found to be the most suitable. In the nitration of pentamethyl-benzene, aluminum trichloride and titanium (IV) chloride cause formation of significant amounts of chlorinated derivatives (e.g., sulfuric acid leads to... 

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