Trimethylbenzenes with

Preparation of phlorogluciaol or its monomethyl ether by reaction of a halogenated phenol with an alkaU metal hydroxide in an inert organic medium by means of a benzyne intermediate has been patented (142). For example, 4-chlororesorcinol reacts with excess potassium hydroxide under nitrogen in refluxing pseudocumene (1,2,4-trimethylbenzene) with the consequent formation of pure phlorogluciaol in 68% yield. In a version of this process, the solvent is omitted but a small amount of water is employed (143). 

The shape selective catalysis was examined by choosing five kinds of the reactions, Eqs. (1) - (5), that is, dehydration of 2-hexanol, decompositions of three kinds of esters and alkylation of 1,3,5-trimethylbenzene with cyclohexene. 

Photolytic. Glyoxal, methylglyoxal, and biacetyl were produced from the photooxidation of 1,2,3-trimethylbenzene by OH radicals in air at 25 °C (Tuazon et al., 1986a). The rate constant for the reaction of 1,2,3-trimethylbenzene and OH radicals at room temperature was 1.53 x 10 " cmVmolecule-sec (Hansen et al., 1975). A rate constant of 1.49 x 10 L/molecule-sec was reported for the reaction of 1,2,3-trimethylbenzene with OH radicals in the gas phase (Darnall et al., 1976). Similarly, a room temperature rate constant of 3.16 x 10 " cm /molecule-sec was reported for the vapor-phase reaction of 1,2,3-trimethylbenzene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 2.69 x lO " cm /molecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). 2,3-Butanedione was the only products identified from the OH radical-initiated reaction of 1,2,4-trimethylbenzene in the presence of nitrogen dioxide. The amount of 2,3-butanedione formed decreased with increased concentration of nitrogen dioxide (Bethel et al., 2000). 

In a similar way, Kim and Bunnett (1970) demonstrated that the substitution of amino group for iodine in iodotrimethylbenzene proceeds via the ion-radical mechanism, in contrast to the bromo and chloro analogs. The reaction of 5- and 6-halo-l,2,4-trimethylbenzenes with potassium amide in liquid ammonia gives rise to 5- and 6-aminoderivatives. This is the cine-substitution reaction (see Scheme 4.12). 

Technical trimethylbenzene with a boiling range of 166-174° is satisfactory. 

Fig. 31. Catalytic activities of acidic Na or Cs salts of HjPW 204o as a function of Na or Cs content, (a) M = Na (O) dehydration of 2-propanol, (A) decomposition of formic acid, ( ) conversion of methanol, ( ) conversion of dimethyl ether, (b) M = Cs (O) dehydration of 2-propanol, ( ) conversion of dimethyl ether, (A) alkylation of 1,3,5-trimethylbenzene with cyclohexene. (From Refs. 46 and 128.)...

Fig. 33. Catalytic activities of various acid catalysts for liquid-phase reactions. TMB Alkylation of 1,3,5-trimethylbenzene with cyclohexene CA Decomposition of cyclohexyl acetate. (From Ref. 47.)...

Reactivity toward electrophilic aromatic substitution increases with increasing number of electronreleasing substituents. Benzene, with no methyl substituents, is the least reactive, followed by toluene, with one methyl group. 1,3,5-Trimethylbenzene, with three methyl substituents, is the most reactive. 

The group B salts of H3PW12O40 are also strong acids unless they are stoichiometrically neutralized. These salts catalyze various kinds of reactions in the liquid phase as solid catalysts. For the alkylation of 1,3,5-trimethylbenzene with cyclohexene, the activity of CS2.5H0.5PW12O40 (abbreviated as CS2.5W) is much higher than those of SC>4 /Zr02 and Nafion. Here, CS2 5W is not soluble and the reactions take place on the surface of the solid. 

The synthesis and characterization of a thalhum(I) triscar-bene complex has been described. The reaction of a chelating tripodal carbene ligand l,3,5- tris(3-rgrr-butyhmidazol-2-ylideno)methyl -2,4,6-trimethylbenzene with Tl(OTf) resulted in the formation of the triscarbene thallium(l) complex (55). An X-ray stmctural determination showed that the tripodal carbene hgand coordinates with the thal-lium(l) ion in (55) in the expected tridentate conformation. 

Problemll.il From the reaction of mesitylene (1,3,5-trimethylbenzene) with HF and BFj, Olah (see p. 346) isolated at low temperatures a bright-yellow solid whose elemental composition corresponds to mesitylene HF BF3 in the ratio 1 1 1. The compound was poorly soluble in organic solvents and, when melted, conducted an electric current chemical analysis showed the presence of the Bp4 ion. When heated, the compound evolved BF3 and regenerated mesitylene. 

Scheme 6.3 Friedel-Crafts reaction of 1,3,5-trimethylbenzene with N-acyliminium ion...

The major products obtained in the alkylation of toluene on these catalysts are xylenes, tri- and tetra-methylbenzenes. The variation of catalytic activity and surface area of the system CsxHs. XPW12O40 as a function of x is shown in Fig.2. It is seen that the catalytic activity reaches a maximum at x = 2.5 and the surface area increases with increase in the extent of substitution. Similar results were obtained in the case of other salts. It has been reported, in the case of cesium salt, that the activity maximum occured at x = 2.5 for the alkylation of 1,2,3 trimethylbenzene with cyclohexene [ 16] and the high activity has been attributed to the high surface acidity of this catalyst. 

Letcher and coworkers investigated the excess heat of mixing of alkynes with different solvents such as cycloalkanes(cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane) with an -alkyne (n-hexyne or n-heptyne or -octyne) bicyclic compounds[decahydronaphthalene (CioHig), bicyclohexyl (CnHii) L2,3,4-tetrahydronaphthalene (C10H12), cyclohexylbenzene (C12H16)] with -hexyne or n-heptyne benzene with n-hexyne , w-heptyne or -octyne and finally, 1,3,5-trimethylbenzene with n-hexyne -heptyne or w-octyne. ... 

For the mixtures 1,3,5-trimethylbenzene + -hexyne the values of are positive and small (//max = 32.5 J mol ), but for the mixture of 1,3,5-trimethylbenzene with -heptyne / ax=- 156.2 J moU for a mixture of 1,3,5-trimethylbenzene with -octyne //max = 231 J mol" For the last two mixtures the excess heat of mixing is negative. This effect could well be due to the inductive effect of the substituted methyl groups increasing the electron density in the aromatic ring and resulting in either an enhanced n-n interaction or an enhanced n (aromatic ring)-H interaction. 

P-lO - Transalkylation of trimethylbenzene with toluene over large pore zeolites... 

For the sake of completeness, it should be mentioned that a further microreactor-based bromination reaction has also been briefly described [29]. The reaction of 1,3,5-trimethylbenzene with elemental bromine gave the monobrominated product in 73% yield. 

In the alkylation of trimethylbenzene with methanol over H-ZSM-5, the 1,2,3,4-isomer fraction in tetramethylbenzenes are very high (to 98%). The selectivity for the isomer is further improved by selective dealumination of the external surface of the zeolite crystals or by selective poisoning of the active sites on the external surface. 

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