Benzenes 1,3,5-trimethylbenzene

Aromatic hydrocarbons (toluene, xylenes, ethyl benzene, trimethylbenzenes, styrene, benzene) Insulation, textiles, disinfectants, plastics, paints, smoking... 

The Tatoray process was originally developed by Toray and is currendy Hcensed by UOP (53—57). A schematic of the process is shown in Figure 4. In this process, toluene or a mixture of toluene and Cg aromatics are reacted to form primarily xylenes and benzene. An equiUbrium distribution of xylenes is produced. As shown in Table 4, the ratio of xylenes to benzene can be adjusted by altering the feed ratio to toluene to aromatics. Trimethylbenzenes are the preferred aromatic compound. 

Polymethylbenzenes (PMBs) are aromatic compounds that contain a benzene ring and three to sis methyl group substituents (for the lower homologues see Benzene Toluene Xylenes and ethylbenzene). Included are the trimethylbenzenes, (mesit iene (1), pseudocumene (2), and hernimeUitene (3)),... 

The Tatoray process, which was developed by Toray Industries, Inc., and is available for Hcense through UOP, can be appHed to the production of xylenes and benzene from feedstock that consists typically of toluene [108-88-3] either alone or blended with aromatics (particularly trimethylbenzenes and ethyl-toluenes). The main reactions are transalkylation (or disproportionation) of toluene to xylene and benzene or of toluene and trimethylbenzenes to xylenes in the vapor phase over a highly selective fixed-bed catalyst in a hydrogen atmosphere at 350—500°C and 1—5 MPa (10—50 atm). Ethyl groups are... 

Dimethylpentane Isopropyl benzene fraMS-2-Pentene 1,2,4-Trimethylbenzene... 

Of the top ten most frequently reported toxic chemicals on the TRI list, the prevalence of volatile chemicals explains the air intensive toxic chemical loading of the refining industry. Nine of the ten most commonly reported toxic chemicals are highly volatile. Seven of the ten are aromatic hydrocarbons (benzene, toluene, xylene, cyclohexane, 1,2,4-trimethylbenzene, and ethylbenzene). 

Arrange the following five compounds in order of decreasing rate of bromination benzene, toluene, o-xylene, i-xylene, 1,3,5-trimethylbenzene (the relative rates are 2 X 10, 5 X 10, 5 X 10 60, and 1). 

Moulijn et al. (33) studied the reactions of some linear alkynes over a W08-Si02 catalyst in a fixed-bed flow reactor. Besides metathesis, cyclotrimerization to benzene derivatives occurred. Thus, propyne yielded, in addition to metathesis products, a mixture of trimethylbenzenes. From this an indication of the mechanism of the metathesis of alkynes can be obtained. 

A kinetic isotope effect, kH/kD = 1.4, has been observed in the bromination of 3-bromo-l,2,4,5-tetramethylbenzene and its 6-deuterated isomer by bromine in nitromethane at 30 °C, and this has been attributed to steric hindrance to the electrophile causing kLx to become significant relative to k 2 (see p. 8)268. A more extensive subsequent investigation304 of the isotope effects obtained for reaction in acetic acid and in nitromethane (in parentheses) revealed the following values mesitylene, 1.1 pentamethylbenzene 1.2 3-methoxy-1,2,4,5-tetramethyl-benzene 1.5 5-t-butyl-1,2,3-trimethylbenzene 1.6 (2.7) 3-bromo-1,2,4,5-tetra-methylbenzene 1.4 and for 1,3,5-tri-f-butylbenzene in acetic acid-dioxan, with silver ion catalyst, kH/kD = 3.6. All of these isotope effects are obtained with hindered compounds, and the larger the steric hindrance, the greater the isotope... 

Not only are there substrates for which the treatment is poor, but it also fails with very powerful electrophiles this is why it is necessary to postulate the encounter complex mentioned on page 680. For example, relative rates of nitration of p-xylene, 1,2,4-trimethylbenzene, and 1,2,3,5-tetramethylbenzene were 1.0, 3.7, and 6.4, though the extra methyl groups should enhance the rates much more (p-xylene itself reacted 295 times faster than benzene). The explanation is that with powerful electrophiles the reaction rate is so rapid (reaction taking place at virtually every encounter between an electrophile and substrate molecule) that the presence of additional activating groups can no longer increase the rate. ... 

Polymethyl-substitated benzene isomers usually are referred to by trivial names such as pseudocumene (1,2,4-trimethylbenzene), mesitylene (1,3,5-trimethylbenzene), and durene (1,2,4,5-tetramethylbenzene). These names were given to these compounds when aromahc compounds were hrst isolated from coal and their structures were as yet not proven. 

The pore size of Cs2.2 and Cs2.1 cannot be determined by the N2 adsorption, so that their pore sizes were estimated from the adsorption of molecules having different molecular size. Table 3 compares the adsorption capacities of Csx for various molecules measured by a microbalance connected directly to an ultrahigh vacuum system [18]. As for the adsorption of benzene (kinetic diameter = 5.9 A [25]) and neopentane (kinetic diameter = 6.2 A [25]), the ratios of the adsorption capacity between Cs2.2 and Cs2.5 were similar to the ratio for N2 adsorption. Of interest are the results of 1,3,5-trimethylbenzene (kinetic diameter = 7.5 A [25]) and triisopropylbenzene (kinetic diameter = 8.5 A [25]). Both adsorbed significantly on Cs2.5, but httle on Cs2.2, indicating that the pore size of Cs2.2 is in the range of 6.2 -7.5 A and that of Cs2.5 is larger than 8.5 A in diameter. In the case of Cs2.1, both benzene and neopentane adsorbed only a little. Hence the pore size of Cs2.1 is less than 5.9 A. These results demonstrate that the pore structure can be controlled by the substitution for H+ by Cs+. 

The catalytic performances obtained during transalkylation of toluene and 1,2,4-trimethylbenzene at 50 50 wt/wt composition over a single catalyst Pt/Z12 and a dualbed catalyst Pt/Z 121 HB are shown in Table 1. As expected, the presence of Pt tends to catalyze hydrogenation of coke precursors and aromatic species to yield undesirable naphthenes (N6 and N7) side products, such as cyclohexane (CH), methylcyclopentane (MCP), methylcyclohexane (MCH), and dimethylcyclopentane (DMCP), which deteriorates the benzene product purity. The product purity of benzene separated in typical benzene distillation towers, commonly termed as simulated benzene purity , can be estimated from the compositions of reactor effluent, such that [3] ... 

Note that in this case, the three carbonyl ligands are staggered relative to the carbon atoms in the benzene ring (as indicated by the dotted vertical lines). Similar compounds have also been prepared containing Mo and W. Methyl-substituted benzenes such as mesitylene (1,3,5-trimethylbenzene), hexamethylbenzene, and other aromatic molecules have been used to prepare complexes with several metals in the zero oxidation state. For example, Mo(CO)6 will react with 1,3,5-C6H3(C]T3)3, 1,3,5-trimethylbenzene, which replaces three carbonyl groups. 

Tatoray [Transalkylation aromatics Toray] A process for transalkylating toluene, and/or trimethylbenzenes, into a mixture of benzene and xylenes. Operated in the vapor phase, with hydrogen, in a fixed bed containing a zeolite catalyst. Developed jointly by Toray Industries and UOP and now licensed by UOP. First operated commercially in Japan in 1969 as of 1992, 23 units were operating and 6 more were in design and construction. 

Figure 6. Transalkylation of an ethylbenzene-xylene feed over HZSM-4. TMB = trimethylbenzene, DMEB = dimethylethyl-benzene, DEB = diethylbenzene, and ETol = ethyltoluene. Feed 16% EB, 62% m-xylene, 22% o-xylene. Temperature ...

The most common by-product losses are due to transalkylation, dealkylation, saturation and cracking. Transalkylation results in toluene, trimethylbenzenes, methylethyl benzenes, benzene and ClOAs. These are the best by-products to have, because they are the easiest to react back into C8A in a transalkylation unit (if the aromatics complex is so equipped) without any loss of carbon atoms [59-61]. Dealkylation results in benzene, toluene, methane and ethane. The benzene and toluene are aromatics and represent valuable by-products, but the C1-C6 nonaromatics represent carbons that are lost from the complex as less valuable LPG and fuel gas. 

Side Reactions One of the major side reactions that occurs during isomerization of Cg aromatics is transalkylation. This reaction produces species such as toluene, trimethylbenzene, methylethylbenzene, dimethylethylbenzene, benzene and diethylbenzene. The types and specific isomers of transalkylated products formed depend on the acidity and spatial constraints of the zeolitic catalyst used. These reactions can be controlled through modification of catalyst properties, especially pore size and external acidity, though these reactions are still among the major contributors to xylene losses. 

Miscible with alcohol, benzene, ether (Windholz et ah, 1983), and trimethylbenzene isomers. Solubility in water ... 

Figure 5 Plots of log versus AG°et for fluorescence quenching of RAcrH" (2.0 x 10 " M) by various electron donors (a) in MeCN and (b) in benzene at 298 K. Numbers refer to electron donors benzene (1), toluene (2), ethylbenzene (3), cumene (4), ra-xylene (5), o-xylene (6), 1, 3, S-ttimethylbenzene (7),/ -xylene (8), 1,3-trimethylbenzene (9), 1, 2,3,4-tetramethylbenzene (11), 1,2,3,5-tetramethylbenzene (12), 1,2,4,5-tetramethylben-zene (13), pentamethylbenzene (14), hexamethylbenzene (15), triphenylamine (16), N,N-dimethylaniline (17), ferrocene (18), and decamethylferrocene (19). (From Ref. 79.)...

We have determined the rate of formation of dimethylethylpyridine, and trimethylbenzene in a batch reactor in the presence of cpCo(cod), which acts as the catalyst precursor. The reaction was found to be of order 1.7 with respect to alkyne and of zero order in nitrile concentration. The Arrhenius energy of activation for the formation of both pyridine and benzene derivatives was calculated to 22.8 kcal/mol (80MI3). 

In agreement with our aforementioned prediction, 98 and 99, both of which comprehend a secondary C2 axis, functioned as effective hosts for benzene, p-xylene, and 1,2,4-trimethylbenzene. " " On the contrary, the other benzo-fused derivatives of tetraphenylene, which are deprived of a secondary C2 axis, did not manifest any inelusion capacity in all solvents tested. ... 

Synonyms The three isomers of trimethyl benzene are mesitylene (1,3,5-trimethylben-zene, sym-trimethylbenzene, 1,3,5-TMB), pseudocumene (1,2,4-trimethyl benzene,... 

The present procedure is the most convenient method for preparation of mono- or diiodo derivatives from various poly-alkylbenzenes in high yields.1 2 Thus 5-i-butyl-1,3-dimethyl-benzene gives 4-<-butyl-2,6-dimethyliodobenzene in 90% yield and 4 - - buty I -1,2 - d imet hy 1 benzene gives 5-<-butyl-2,3-dimethyl-iodobenzene in 81% yield. 5- -Butyl-l,2,3-trimethylbenzene,... 

T he petroleum industry entered the field of aromatics production largely because the unprecedented demand for toluene for the manufacture of TNT at the outbreak of World War II in 1939 could not be met by other sources. As a result of its efforts, the industry supplied 75 to 85% of all the toluene which was nitrated for TNT production during the latter years of World War II. Since that time the petroleum refiners have remained in the field and at present they are major suppliers of toluene and xylenes. In Table I it is shown that in 1949 about 59% of the toluene and 84% of the xylenes produced in the United States were derived from petroleum sources. The petroleum industry has diversified its operations in the field of aromatics production until at present a variety of materials is offered. Table II presents a partial list of the commercially available aromatics, together with some of their uses. A number of other aromatics, such as methylethyl-benzene and trimethylbenzene, have been separated in small scale lots both as mixtures and as pure compounds. 

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