Toluene formation

Derive an expression for the rate of toluene formation, assuming that the reactions occur in the forward direction only and that the surface coverage of toluene is much larger than that of methylcyclohexane, while desorption of toluene determines the overall rate. 

The cut-and-paste technique has two steps (i) M (or P) screw-sense-selective photolysis at the longer kmax region in CC14 to form P (or M) screw sense telomers with Si-Cl termini, and (ii) Na-mediated recondensation of the telomers in hot toluene. Formation of an optically active helical polysilane with an almost single screw sense was evidenced by significant changes in the UV and CD spectra after the cut-and-paste technique, as shown in Figure 4.6b. 

The reaction of toluene formation from benzene and methyl alcohol can be represented by the following scheme ... 

It will be interesting to see whether further reports with more precise analytical data than those heretofore offered (89,90) will be forthcoming. Evidence ruling out the possibility of toluene formation by chain growth in Fischer-Tropsch synthesis followed by dehydrocyclization would also be necessary for a confirmation of the methylation of benzene as suggested by Eidus (89). 

Nametkin and Kagan (249) studied the mechanism of methyl transfer in the xylene-benzene-AICI3 system. They used a flow system operating at 0.252 space velocity, 1 atm., and 250° and 300°, with 20 and 40% AICI3 on charcoal. Benzene in the absence of xylene is not affected. With an equimolar mixture of benzene and xylene, toluene formation reached 25% with 40% A1C13 half as much was obtained with 20% AICI3. Benzene disappearance was less than toluene formation so that... 

This coke profile can be used to explain why the maximum reaction rate for toluene formation shifted from the Inlet to the outlet. With the fresh catalyst, the greater the concentration of n-heptane, the greater the rate of toluene formation. This is represented by the curve at time t=0 In Figure 6. When the catalyst is deactivated by coke, the first section loses more activity than the others. Therefore, one point downstream of the first section has greater dehydrocyctization activity. Its toluene formation rate is the highest due to less deactivation compared to its upstream section, and to higher n-heptane concentration compared to its downstream section. 

Typically, there is less methane and ethylene present in the effluent of a reactor than would be expected from the benzene and toluene formation. Carbon monoxide is generally about 10mol% of the total carbon oxides. 

The quantum yield for toluene formation is very low in solution but approaches unity in the gas phase at low pressures- . The toluene was suggested to be formed from vibrationally excited ground state molecules, following rapid internal conversion from the excited singlet state manifold, perhaps involving the intermediacy of norcaradiene... 

Cycloheptatriene (4) upon irradiation in ether solution gives the bicyclic photoisomer 5 16>. Cycloheptatriene is regenerated upon pyrolysis of 5. Photolysis of 4 in the vapor phase 17> leads to the formation of toluene (6) as well as 5. The quantum yield for toluene formation increases with decreasing pressure, the extrapolated value at zero pressure being unity within experimental error. Under the most favorable conditions, no more than five percent of the excited cycloheptatriene molecules iso-merize to 5. Srinivasan 17> has suggested that isomerization to toluene... 

As it is mentioned earlier, there is a significant change in selectivities of toluene and Cg+ aromatics with the addition of zinc. The preferential increase of toluene indicates the possibility of toluene formation from the direet dChydrocyclization/direct aromatization of n-heptane over the Zn/HZSM-5 (Kms), in addition to the cracking-and-oligomerization route (Kai). The direct dehydrocyclization of hydrocarbons (hexane and above) was also reported by Giannetto et al [49] from their studies over Ga-HZSM-5 catalyst. 

Pathways (I) and (ll) have been respectively postulated in (2) and (5). In order to determine which of the steps (I) or (II) are the most probable we have studied, over Ga-HZSM-5 the rate of benzene (or toluene) formation starting from molecules considered as possible intermediates during the propane aromatization. 

Rate of benzene or toluene formation for different reactants, T = 773 K, P -ic = 0.12 torr. 

The main product of the reaction was dibenzyalmine. As seen in Figure 16 the selectivity of dibenzylamine was around 75 % and was not influenced by the level of the surface Sn/Pt atomic ratio. Upon increasing the surface Sn/Pt atomic ratio the selectivity of toluene formation decreased and that of the primary amine increased. 

Figures 10-12 show the measured rates of formation of toluene, phenylacetylene, and styrene compared with the rates predicted by Reactions 10-12. Of these three, only toluene (Figure 10) shows a serious disagreement between prediction and observation. The early decline in the toluene formation rate ( v 7 5 mm) may be due to rapid benzyl radical formation. A cursory examination of the C7H7 and C7Hg flux profiles in Figure 8 supports this possibility. Nevertheless, the magnitude of discrepancy between measured and predicted rates suggests that some other mechanism is probably responsible for toluene formation in this system.

Figure 10. Comparison of measured net rates of toluene formation with predicted formation rates for near-sooting. Conditions same as in Figure 2.

The complexes were heterogenized from their aqueous and methanol solutions in the atmosphere of Ar, as described in [2]. The experiments were performed in a reaction vessel with a magnetic stirrer, equipped by a water jacket, reflux condenser, and sampling device [1]. We loaded 0.05 - 0.1 g of the catalyst (4.95 X 10- g-atom of Ru) and 0.025 g of NaBH4 into the reaction vessel, filled the system with Ar (or air), added 5 ml of propanol-2, stirred the reaction mixture at 82.5° for some definite time period to activate the catalyst, and then added p-BT (9.9 x 10- - 4.95 x 10- mole). The composition of the catalyzate was analyzed by gas-liquid chromatography. The activity of the catalysts was characterized by the initial specific rate of toluene formation (W, ... 

No. of catalyst Complex to be immobilized Initial specific rate of toluene formation W, mole/min-mole Ru(Rh), in the atmosphere of ... 

Assuming a steady state with respect to the concentration of Intermediate radicals and atoms, theoretical rate equations were derived and those were found to be Identical with the experimental equations (see Table I and Table II-A) for the relatively low hydrogen partial pressures of up to < 73 bar. In further testing the applicability of this mechanism under more extended experimental conditions. It was found that the kinetics of the toluene formation was different at a hydrogen partial pressure of 230 bar. At the latter hydrogen pressure a rate equation of... 

A novel jS-elimination of haloform from A-monosubstituted trihaloacetamides can be used to form isocyanates at room temperature (X = Br) or at elevated temperatures in a polar solvent (X = Cl) the corresponding trifluoro derivatives are unreactive. The rates of gas-phase pyrolytic elimination of primary, secondary, and tertiary 2-hydroxyalkylbenzenes increase slightly in the order stated, as eliminative dehydration gives way to toluene formation. The kinetics of acid-catalysed dehydration of propan-1- and-2-ol in hot compressed liquid water have been discussed with particular reference to the role of unstable ether intermediates. ... 

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