Toluene, other-substituted

Toluene (methylbenzene) is similar to benzene as a mononuclear aromatic, but it is more active due to presence of tbe electron-donating metbyl group. However, toluene is much less useful than benzene because it produces more polysubstituted products. Most of tbe toluene extracted for cbemical use is converted to benzene via dealkylation or disproportionation. Tbe rest is used to produce a limited number of petro-cbemicals. Tbe main reactions related to tbe cbemical use of toluene (other than conversion to benzene) are the oxidation of the methyl substituent and the hydrogenation of the phenyl group. Electrophilic substitution is limited to the nitration of toluene for producing mono-nitrotoluene and dinitrotoluenes. These compounds are important synthetic intermediates. 

A. The Evaluation of Reaction Constants Sufficient information is presented for toluene and the other substituted benzenes to permit the assignment of reaction constants for many reactions. The uncertainty in the p constants depends on the quality of the [Pg.94]

Our initial experiments were performed on p-chlorobenzyl alcohol and employed two equivalents of CuCl Phen. It was rather disappointing to find that, beside NaOAc, all the other bases tested were far less efficient than K2C03 (10). However, during the course of these optimization studies, a dramatic influence of the solvent on the reaction rate was uncovered. For example, a 3-4-fold acceleration was obtained when toluene was substituted for benzene. In contrast, replacing benzene by m- or p-xylene resulted in a decrease in the rate... 

Nitrotoluenes and other substituted toluenes are not sufficiently acidic to be chlorinated by CC14 in basic environment, but partially a-chlorinated methylbenzenes do react to yield substituted benzotrichlorides (equation 74)622. 

Isomerism of the tri- and tetra- substituted toluenes will not be considered at length. The chlorine substitution products in which more than one chlorine is substituted may likewise occur in still another isomeric form. Instead of the two chlorines or other substituting elements or groups both entering the ring or the side chain, we may have compounds in which one or more elements enter one position, and at the same time, one or more enter the other position. Such compounds are known, but will simply be mentioned by formula, e.g. 

The invention described in this patent is the combination of using a supercritical fluid to dissolve the desired components from tar sands and to recover regeneratively heat from the tar free sand leaving the exu actor. Tar sands are fed to an extractor where they are contacted countercunently with supercritical aromatic solvents such as benzene, toluene, or other substituted benzenes, or with supercritical cycloaliphatic solvents such... 

In 1982, Van, Zhang, Jiang and Hu41 (VZJH) reported the heats of combustion and formation of benzenesulphonamide and two of its methyl (i.e. toluene) derivatives, x-RC6H4S02NH2 R = H, 24a x-R = 2 and 4-Me, 67a and 67b, respectively. These findings are presented in Table 11. The results are internally consistent. The relative isomer stabilities of 67a and 67b is qualitatively and quantitatively consistent with that of other substituted benzenes [e.g. <5AHf(s, 37b, 37d) = 0.8 kcal mol-1]. In addition, that either of the isomeric toluenesulphonamides, 67a and 67b, is some 9 kcal mol-1 lower than that of... 

The use of other reactants or modifiers such as toluene sulfonamide, substituted ureas, and substituted triazines is expected to increase. 

For instance, the reaction of EtaSiH and 2 equiv. of p-methoxystyrene in toluene with 1.0 mol% of 16a afforded at 100°C within 6 h the dehydrogenative silylation product ( )-l-(p-methoxystyryl)-2-(triethyl-silyl)ethylene in 95% yield. The reaction is of high selectivity that neither (Z)-isomers, nor branched dehydrogenative silylation products were seen. Less hydridic silanes, such as triphenylsilane, were less efficient than for instance EtsSiH. Other substituted styrenes such as p-methyl, p-chloro-, and p-fluorostyrene also afforded the corresponding tran -vinylsilanes in high yields and selectivities (up to 98%). In the case of aliphatic alkenes, such as -octene, allyltriethoxysilane, vinylcyclohexane, and ethylene, dehydrogenative silylations were still preferred, but showed less E/Z selectivity. Cyclic olefins, such as cyclooctene, furnished low conversions under the same reaction crmditions. The results are summarized in Scheme 19. 

Other substitution reactions include those with ff,ff-dimethyl-0--(methylsulphonyl)hydroxylamine to provide dimethylaminocyclo-pentadiene, [27], with dimethyl disulphide and sodium hydride to give the penta(methylthio)cyclopentadienide anion, [28], and the important reaction with toluene-p-sulphonazide which provides diazocyclo-pentadiene [30]. 

Where selective introduction of substituents into the anthraquinone molecule is difficult, synthesis from smaller components is frequently used. The most important reaction component in this context is phthalic anhydride, which undergoes Friedel-Crafts reaction with other substituted aromatics such as chlorobenzene, chlorophenol or toluene to yield the desired anthraquinone derivative. 

H abstraction by the COi radical is only supported by one of the routes proposed for the formation of benzoic acid in our experiments with benzene. If such a reaction chaimel were of importance, formation of substituted benzoic acids should have been observed for other substituted benzenes, as the dissociation energy of the C—bonds in these compounds is expected to he of the same order as in benzene. Moreover, formation of products derived from the henzyl radical was not observed in our experiments with toluene. We therefore conclude that the contrihution of H-abstraction channel by C02 radical ions as a potential reaction channel of this intermediate is neghgihle under our experimental conditions. 

The rates of electrophilic substitution on other even aromatic systems, and the effects of substituents, can be deduced in the usual way. Thus since -1- / substituents destabilize odd AH cations while — / substituents stabilize them, substitution should tend to take place in such a way as to ensure that + / substituents are at inactive positions in the arenonium intermediate and - / substituents at active positions. For example, in benzene, where the positions ortho and para to the point of substitution are active in the intermediate benzonium ion (89), +/ substituents (e.g., CF3) are best placed in the meta position, while — / substituents (e.g., CH3) should be ortho or para. Benzotrifluoride (PhCF3) consequently substitutes mainly meta, nitration, for example, giving (90), while toluene (PhCH3) substitutes mainly ortho and para, giving, e.g., (91) and (92) on nitration. 

If, on the other hand, the encounter pair were an oriented structure, positional selectivity could be retained for a different reason and in a different quantitative sense. Thus, a monosubstituted benzene derivative in which the substituent was sufficiently powerfully activating would react with the electrophile to give three different encounter pairs two of these would more readily proceed to the substitution products than to the starting materials, whilst the third might more readily break up than go to products. In the limit the first two would be giving substitution at the encounter rate and, in the absence of steric effects, products in the statistical ratio whilst the third would not. If we consider particular cases, there is nothing in the rather inadequate data available to discourage the view that, for example, in the cases of toluene or phenol, which in sulphuric acid are nitrated at or near the encounter rate, the... 

An old name for benzene was phene and its hydroxyl derivative came to be called phe nol This like many other entrenched common names is an acceptable lUPAC name Likewise o m and p cresol are acceptable names for the various ring substituted hydroxyl derivatives of toluene More highly substituted compounds are named as deriv atives of phenol Numbering of the ring begins at the hydroxyl substituted carbon and proceeds m the direction that gives the lower number to the next substituted carbon Sub stituents are cited m alphabetical order... 

Toluene, an aLkylben2ene, has the chemistry typical of each example of this type of compound. However, the typical aromatic ring or alkene reactions are affected by the presence of the other group as a substituent. Except for hydrogenation and oxidation, the most important reactions involve either electrophilic substitution in the aromatic ring or free-radical substitution on the methyl group. Addition reactions to the double bonds of the ring and disproportionation of two toluene molecules to yield one molecule of benzene and one molecule of xylene also occur. 

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