Toluene nuclear chlorination

The PMBs, when treated with electrophilic reagents, show much higher reaction rates than the five lower molecular weight homologues (benzene, toluene, (9-, m- and -xylene), because the benzene nucleus is highly activated by the attached methyl groups (Table 2). The PMBs have reaction rates for electrophilic substitution ranging from 7.6 times faster (sulfonylation of durene) to ca 607,000 times faster (nuclear chlorination of durene) than benzene. With rare exception, the PMBs react faster than toluene and the three isomeric dimethylbenzenes (xylenes). 

The side-chain substitution of toluene, p-chlorotoluene, etc. is industrially practised. This reaction is carried out in a photochemical reactor. It is an exothermic reaction in which HCl is produced. The reaction is consecutive, and hence CL first reacts with toluene reacts to form the desired benzyl chloride, which is then converted to benzal chloride, and finally benzotrichloride. We may, however, well be interested in the selectivity to benzyl chloride. An additional complication arises due to nuclear chlorination, which is most undesirable. A distillation-column reactor can offer advantages (Xu and Dudukovic, 1999). 

The electrochemical nuclear chlorination of substituted aromatics in some cases allows to achieve better regioselectivities than the chemical alternatives. DOW 93 94) has shown that, in the anodic chlorination of toluene in aprotic electrolytes, the p/o ratio of the chlorotoluenes can be increased to about 2.2 (chemical alternatives 0.5-1, depending on substances added to the reaction mixture) ... 

Chlorination of toluene, chlorobenzene, 1,2-dichlorobenzene and naphthalene with chlorine gas is eatalyzed by zeolite catalysts. There is a great potential and possibility for the use of zeolite catalysts in the nuclear chlorination of aromatics in the liquid phase instead of the Lewis acid catalysts like FeCla and AICI3 used at present. The use of zeolites in such cases leads to enhanced yield of the para-isomer thereby lowering the formation of byproducts and the cost of separation. 

The chlorination of toluene in the absence of catalysts that promote nuclear substitution occurs preferentially in the side chain. The reaction is promoted by free-radical initiators such as ultraviolet light or peroxides. Chlorination takes place in a stepwise manner and can be controlled to give good yields of the intermediate chlorination products. Small amounts of sequestering agents are sometimes used to remove trace amounts of heavy-metal ions that cause ring chlorination. 

If chlorine and bromine are allowed to act upon an aromatic hydrocarbon like toluene, which has a side-chain, substitution may occur in the nucleus or the side-chain, according to the conditions. Generally speaking, in the cold and in presence of a halogen carrier, nuclear substitution occurs, Irut at a high temperatuie the halogen passes into the side-chain (see Piep. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

Juenge3 has now found that the reagent is effective for nuclear or side-chain halogenation of aromatic systems, the former occurring under ionic conditions, the latter under free-radical conditions. Thus benzene and naphthalene are chlorinated under Lewis acid catalysis 1 -chloronaphthalene can be prepared in 58% yield. Toluene under similar conditions gives a mixture of 2- and 4-chloro-toluene in 66% yield. In the presence of benzoyl peroxide, benzyl chloride is obtained in 44% yield. 

Benzylidene chloride and its nuclear-substituted derivatives are important mainly as intermediates on the way to aldehydes, so that the difficulty of separating them from benzotri-chlorides must be overcome. On hydrolysis they give benzoic acids, which are readily separable from the aldehydes. Phosphorus trichloride (ca. 2%) has been recommended as addition for side-chain chlorination of toluenes. 

Interestingly, H(//-H)Os3(CO)io(NH3) is stable for a long time in the presence of NH3 but it decomposes when dissolved in chlorinated solvents yielding 1 and free NH3. The compound seemed, however, to be sufficiently stable in toluene solution to enable complete characterization in solution by H and C NMR spectroscopy. By comparing the NMR spectra obtained in solution (at —80 °C) (Fig. 3) and in the solid state (room temperature, CPMAS) and by measuring the nuclear Overhauser effect between the NH3 and the hydride resonances it was possible to establish that in solution and in the solid state H(,u-H)Os3(CO)io(NH3) adopts... 

The question of ami nation of aromatics by protonated amino radicals has been examined extensively by Minisci and co-workers (16). Benzene is aminated in good yields by a variety of N-chloroamines in acidic solutions, catalyzed by Iron(II) sulfates. With activated aromatics competing chlorination and sulfonation complicates the reactions, but In many cases good yields of the substituted anilines are obtained. In the case of a1kylbenzenes, benzylic chlorination competes with nuclear amlnatlon. The latter is favored by high acid concentrations. Thus, the reaction of toluene with N-chlorodimethyl amine (17) gives 95 percent amination and 6 percent benzylic chlorination in neat H SO., but 100 percent benzylic chlorination In neat acetic acid. The amount of nuclear amination increases with the concentration of H2SO4 in acetic acid. 

---