Xylene, o-and

Entry 22-24 shows competitive recrystallization from 1 1 mixtures of xylene isomers [34], In contrast to mono-alkylbenzenes, m-xylene and //-xylene were exclusively included in CA cavities from mixtures of o- and m-xylene, o- and p-xylene, respectively, i.e. //-xylene acts as a solvent and is not included in the CA host cavity at all. Recrystallization from a 1 1 mixture of m-xylene and //-xylene yielded a crystal that included both guest components in a similar guest ratio... 

Fig. 30. Influence of the solvent concentration on the PEO melting temperature Tf for the copolymer BEO.l in solution in xylene (o), and in acetic acid (o)269)...

Figure 13.5 shows a flowsheet for the manufacture of phthalic anhydride by the oxidation of o-xylene. Air and o-xylene are heated and mixed in a Venturi, where the o-xylene vaporizes. The reaction mixture enters a tubular catalytic reactor. The heat of reaction is removed from the reactor by recirculation of molten salt. The temperature control in the reactor would be diflficult to maintain by methods other than molten salt. 

Catalysts used in the polymerization of C-5 diolefins and olefins, and monovinyl aromatic monomers, foUow closely with the systems used in the synthesis of aHphatic resins. Typical catalyst systems are AlCl, AIBr., AlCl —HCl—o-xylene complexes and sludges obtained from the Friedel-Crafts alkylation of benzene. Boron trifluoride and its complexes, as weU as TiCl and SnCl, have been found to result in lower yields and higher oligomer content in C-5 and aromatic modified C-5 polymerizations. 

The mother Hquoi obtained from the crystallization, or the raffinate after removal by adsorption, is isomerized using an acidic catalyst to convert xylene to the o- and -isomers (Unit K in Fig. 8). 

Benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylcne. butylbenzene, styrene, o-, m-, and p-diethylbenzenes... 

Acetoxylation has been found to accompany the nitration of o- and m-xylene... 

The use of ethylene dichloride as solvent was extended by Brown et al. 11 to the determination of the kinetics of benzoylation of other aromatics, using benzoyl chloride catalysed by aluminium chloride, and the data are included in Table 109 the relative reactivities are thus benzene, 1.0 toluene, 117 o-xylene, 1,393 m-xylene, 3,960 and p-xylene, 243 and these values are closely similar to those obtained with nitrobenzene as solvent. No exact comparison of the coefficients with those of Corriu et al. 16 is possible because of the different temperatures employed, but the rates appear to be comparable for the two sets of data after allowing for reasonable temperature dependencies. 

Iodosobenzene diacetate is best prepared by the action of peracetic acid and acetic acid on iodobenzene. The present procedure is superior to earlier ones 5-8 because it uses inexpensive, commercially available peracetic acid, is faster, and gives higher yields. The procedure seems general for aiyl iodides with electron-releasing substituents, for the submitters have obtained good yields of diacetates from o-, m- and />-iodoto uene, 2- and 4-iodo-wt-xyiene, 2-iodo-/>-xylene, o-iodophenetole, and 4-iodobi-phenyl. 

Since their development in 1974 ZSM-5 zeolites have had considerable commercial success. ZSM-5 has a 10-membered ring-pore aperture of 0.55 nm (hence the 5 in ZSM-5), which is an ideal dimension for carrying out selective transformations on small aromatic substrates. Being the feedstock for PET, / -xylene is the most useful of the xylene isomers. The Bronsted acid form of ZSM-5, H-ZSM-5, is used to produce p-xylene selectively through toluene alkylation with methanol, xylene isomerization and toluene disproportionation (Figure 4.4). This is an example of a product selective reaction in which the reactant (toluene) is small enough to enter the pore but some of the initial products formed (o and w-xylene) are too large to diffuse rapidly out of the pore. /7-Xylene can, however. 

Kim D, J-C Chae, GJ Zylstra, Y-S Kim, MH Nam, YM Kim, E Kim (2004) Identification of a novel dioxygenase involved in metabolism of o-xylene, toluene, and ethylbenzene by Rhodococcus sp. strain DK17. Appl Environ Microbiol 70 7086-7092. 

When a microporous material, e.g. a zeolite, is used as a catalyst, only those molecules whose diameters are small enough to enter or pass through the pores can react and leave the catalyst. This is the basis for so-called shape-selectivity (Fig. 3.40). Reactant selectivity is encountered when a fraction of the feed molecules can enter the zeolite, whereas the other fraction cannot. For the molecules produced in the interior the same reasoning applies. The favoured products are the less bulky ones, i.e. those with diameters smaller than the pores of the zeolites. For instance, in the zeolite represented in Fig. 3.40 the production of p-xylene is favoured over the production of o- and m-xylenes. Also the bulkiness of the transition state can lead to a different. selectivity, as shown in the last example in Fig 3.40. 

Mixtures of isomers, such as o-, m- and / -xylene mixtures, and adjacent members of homologous series, such as n-hexane-n-heptane and benzene-toluene mixtures, give close to ideal liquid-phase behavior. For this case, yt = 1, and Equation 4.28 simplifies to ... 

Attempts to sensitize this reaction resulted in no product formation, suggesting participation of a benzene singlet in the direct photolysis. Irradiation of isoprene in excess benzene resulted in products similar to those observed with butadiene/7 Irradiation of toluene and o- and p-xylene in the presence of isoprene yielded products similar to (62).<72)... 

Neopentane does not undergo isomerization 185) on chromia/alumina (non-acidic) at 537°C, the only significant reaction been hydrogenolysis to methane and iso-C4. However, the reality of isomerization is made clear from, for instance, the formation of xylenes from 2,3,4-trimethylpentane. For o- and p-xylene, the reactions are (24) and (25) 182, 93). These processes are formally quite analogous to those we have described in previous... 

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