Toluene exchange reactions

ScuriMi - l. Exchange reaction between (phenylalkyl)siUinc and toluene. 

To confirm the production of benzene from the decomposition reaction of methyl(triphenylmethyl)dichlorosilane, the decomposition reaction of methyKdi-phenylmethyl)dichlorosilane in the presence of aluminum chloride was carried out in toluene solvent at 80 C. In this reaction, the exchange reaction between phenyl groups on the methyl group of (diphenylmethyl)(inethyl)dichlorosilane and toluene occurred to give [phenyl(tolyl)methylJ(methyl)dichlorosilane and (di-tolylmethyl)(methyl)dichlorosiIane (Scheme 1). " ... 

The exchange reaction between Np(VI) and Np(V) has been investigated using the isotopic method ( Np) and an extraction separation (Np(VI) with tri-butylphosphate or thenoyltrifluoroacetone in toluene) Cohen et al. have found, for the exchange in perchlorate media, a rate law... 

The first authenticated borole (94) was made by the exchange reaction of phenylboron dichloride with l,l-dimethyl-2,3,4,5-tetraphenylstannole (93) (Eq. 29)w in toluene. 

MP borohydride catches one equivalent of the titanium catalyst, while the polystyrene-bound diethanolamine resin (PS-DEAM) can scavenge the remaining titanium catalyst. The borohydride reagent also assists in the reductive animation reaction. Final purification of the crude amine product is achieved with a polystyrene-bound toluene sulfonic acid resin scavenger that holds the amine through an ion exchange reaction, while impurities are washed off. The pure amine can be recovered with methanol containing 2M ammonium hydroxide. 

In a very similar way, hydroxy functionalized ATRP initiators such as 2,2,2-tribromoethanol can be used for the simultaneous polymerization of eCL and MMA (Scheme 25) [83]. Purposely, the ROP of eCL is promoted by Al(OfPr)3 added in catalytic amount so that the rapid alcohol-alkoxide exchange reaction (see Sect. 2.4) activates all the hydroxyl functions. In order to avoid initiation by the isopropoxy groups of Al(0/Pr)3. The in-situ formed zPrOH is removed by distillation of the zPrOH/toluene azeotrope. On the other hand, the ATRP of MMA is catalyzed by NiBr2(PPh3)3. The two aforementioned one-step methods provide block copolymers with controlled composition and molecular weights, but with a slightly broad MWD (PDI=1.5-2). 

The buzzword polarity, derived from the dielectric approach, is certainly the most popular word concerning solvent effects. (It is the basis for the famous rule of thumb similia similibus solventur, i.e., like dissolves like in English.) We should add like helps like. Let us compare toluene and n-hexane as solvents. At temperatures when both solvents have comparable viscosity, the reaction between 1,2,4,5-tetrafluorobenzene and its anion-radical proceeds in different ways (Werst 1993), depending on the solvent. In toluene, the reaction consists of electron exchange ... 

The second aim of this work is to demonstrate the catalysis of the interlayer anions in organic reactions such as halide-exchange reactions between alkyl halides in toluene (eq. 1). 

For the halide-exchange reactions, into a SO-cm flask equipped with a condenser, 30 cm of toluene or DMF as a solvent and 1.0 g portion of the hydrotalcite-like material (3.3 mmol of interlayer Cl anions) were introduced. A 33 mmol of benzyl chloride was added to the mixture and the temperature was kept at 343 or 373 K with stirring, followed by the addition of a given amount of an alkyl bromide (or iodide) (33-195 mmol). Reactions were conducted under a nitrogen atmosphere. The liquid phase was withdrawn periodically and analyzed by a gas chromatograph equipped with a 2-m long SE-30 column and a... 

The hydrotalcite-1ike material catalyzes organic reactions in which the interlayer Cl" anions play the role of catalyst. The material catalyzed the halide-exchange reactions between benzyl chloride with butyl bromide or butyl iodide in toluene. The hydrota1cite-1ike material also catalyzes a disproportionation of trimethoxysilane to give silane and tetramethoxysilane. 

The dependence of kobsd on stirring speed for Br-I exchange reactions with polymer-supported crown ethers 34 and 35 has been determined under the same conditions as with polymer-supported phosphonium salts 1 and 4149). Reaction conditions were 90 °C, 0.02 molar equiv of 100-200 mesh catalyst, 16-17% RS, 2% CL, 20 mmol of 1-bromooctane, 200 mmol of KI, 20 ml of toluene, and 30 ml of water. Reaction rates with 34 and 35 increased with increased stirring speed up to 400 rpm, and were constant above that value. This result resembles that with polymer-supported onium ion catalysts and indicates that mass transfer as a limiting factor can be removed in experiments carried out at stirring speeds of 500-600 rpm, whatever kind of polymer-supported phase transfer catalyst is used. 

The activity of polymer-supported crown ethers depends on solvent. As shown in Fig. 11, rates for Br-I exchange reactions with catalysts 34 and 41 increased with a change in solvent from toluene to chlorobenzene. Since the reaction with catalyst 34 is limited substantially by intrinsic reactivity (Fig. 10), the rate increase must be due to an increase in intrinsic reactivity. The reaction with catalyst 41 is limited by both intrinsic reactivity and intraparticle diffusion (Fig. 10), and the rate increase from toluene to chlorobenzene corresponds with increases in both parameters. Solvent effects on rates with polymer-supported phase transfer catalysts differ from those with soluble phase transfer catalysts60. With the soluble catalysts rates increase (for a limited number of reactions) with decreased polarity of solvent60), while with the polymeric catalysts rates increase with increased polarity of solvent74). Solvents swell polymer-supported catalysts and influence the microenvironment of active sites as well as intraparticle diffusion. The microenvironment, especially hydration... 

Cinneide and Clarke (770) have studied the activity of Pd-Au films for the deuteration and exchange of benzene and the hydrogenation of p-xylene. The authors report that the activity for the exchange reaction between benzene and deuterium persists to the palladium-lean compositions, which is in agreement with results obtained by Honex et al. (Ill) in a study of the exchange of toluene over alloys of the same kind. The rates are much reduced (by 102 to 103) compared to those found with palladium-rich films. 

S. (-)-(Camphorsulfonyl)imine. A 1 -L, round-bottomed flask is equipped with a two-inch egg-shaped magnetic stirring bar, a Dean-Stark water separator, and a double-walled condenser containing a mineral oil bubbler connected to an inert gas source. Into the flask are placed 5 g of Amberylst 15 ion exchange resin (Note 4) and 41.5 g of the crude (+)-(1 S)-camphorsulfonamide in 500 mL of toluene. The reaction mixture is heated at reflux for 4 hr. After the reaction flask is cooled, but while it is still warm (40-50°C), 200 mL of methylene chloride is slowly added to dissolve any (camphorsulfonyl)imine that crystallizes. The solution is filtered through a 150-mL sintered glass funnel of coarse porosity and the reaction flask and filter funnel are washed with an additional 75 mL of methylene chloride. 

The exchange reactions of organyltrialkoxysilanes with THEA mostly require heating of the components in an appropriate inert solvent (benzene, toluene, xylene, anisole, chloroform, methanol, ethanol etc.) for a long time. However, in some cases the reactions can be carried out at room temperature or, if necessary, with cooling. The transetherification rates and silatrane yields increase in the presence of an alkali metal hydroxide or alkoxide as a basic catalyst. 

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