Benzene by chlorination

Replacement of a hydrogen of benzene by chlorine is termed chlorination. When one or more hydrogens are replaced by an -NO2 (nitro group), it is called nitration. Reaction of benzene with sulfuric acid, a reaction known as sulfonation, leads to a sulfonic acid. Note that in each substitution reaction, a small hydrogen-containing compound is formed. 

Chlorobenzene is used m the production nt phenol, ont line, biphenyl, polychlorobcnzcne. and DOT It is produced from benzene by chlorine substtlalion or oxychlnrination. 

There are in principle three possibilities for reaction of halogens with aromatic hydrocarbons, namely, addition, substitution in the nucleus, and substitution in a side chain. The last of these is discussed on pages 152 and 157. Substitution of benzene by chlorine or bromine is an ionic reaction,114 whereas photochemical or peroxide-catalyzed addition of these halogens involves a radical-chain mechanism.115 Substitution in the side chain also proceeds by a radical mechanism,116 addition rather than side-chain substitution being favored by higher chlorine concentrations.115... 

Figure 6. Commercial activation of benzene by chlorine oxidation.

An ab initio MO study of the mechanism of chlorination of benzene by chlorine in the presence of aluminium chloride has appeared. The rate-limiting stage leads to the formation of the ion-pair complex CeHeCl AlCU" without the explicit formation of Cl, the formation of C-Cl and Al-Cl bonds occurring synchronously with the breaking of the Cl-Cl bond. The introduction of a 3-chloro substituent into benzoyl chloride deactivates the system to further chlorination at the 5-position by a factor of about 6. ° Benzene, toluene, the xylenes, durene, mesitylene, nitrobenzene, and p-nitrotoluene are selectively brominated at 50-65 °C in an HBr-HN03-H2S04-H20 mixture with the participation of oxygen. The small catalytic amount of nitric acid oxidizes HBr to Br+, which reacts with the aromatic compound, and the nitrous acid formed reacts... 

Primarily, to calculate the reactivity index at the ground state of both the closed systems methane (CH4) and benzene (CgHg) along with their chlorine-substituted compounds are chosen because methane and benzene is the doorway of the understanding of the properties of larger aliphatic and aromatic compound, respectively. A systematic substitution of hydrogen for both the moieties (methane and benzene) by chlorine was performed to get all the chlorine-substituted products until CCI4 and CeCl, respectively. At first, those molecules are optimized with DPT at their neutral state and as well as cationic and anionic forms. The reactivity index values and the relative reactivity indices for individual centers of the series of chlorine-substituted methane and benzene-related compounds were computed. These molecules with the optimized structure were then subjected to the weak electric field to get the response function, followed by Cl calculation with... 

BHC is manufactured by chlorination of benzene in the presence of ultra-violet light. The gamma-isomer is obtained from the crude mixture by selective crystallization, and forms colourless crystals, m.p. I13" C. U.S. production 1980 400 tonnes. 

The chlorination of benzene can theoretically produce 12 different chlorobenzenes. With the exception of 1,3-dichlorobenzene, 1,3,5-trichlorobenzene, and 1,2,3,5-tetrachlorobenzene, all of the compounds are produced readily by chlorinating benzene in the presence of a Friedel-Crafts catalyst (see Friedel-CRAFTS reactions). The usual catalyst is ferric chloride either as such or generated in situ by exposing a large surface of iron to the Hquid being chlorinated. With the exception of hexachlorobenzene, each compound can be further chlorinated therefore, the finished product is always a mixture of chlorobenzenes. Refined products are obtained by distillation and crystallization. 

All of the chlorobenzenes are now produced by chlorination of benzene in the Hquid phase. Ferric chloride is the most common catalyst. Although precautions are taken to keep water out of the system, it is possible that the FeCl3H20 complex catalyst is present in most operations owing to traces of moisture in benzene entering the reactor. This FeCl3H20 complex is probably the most effective catalyst (13). 

Benzal chloride can be manufactured in 70% yield by chlorination with 2.0—2.2 moles of chlorine per mole of toluene. The benzal chloride is purified by distillation. Benzal chloride is also formed by the reaction of dichlorocarbene ( CCl2) with benzene (49). 

Liquid benzene is chlorinated in the presence of metalhc iron turnings or Raschig rings at 40 to 60°C (104 to 140°F). Carbon tetrachloride is made from CS9 by bubbling chlorine into it in the presence of iron powder at 30°C (86°F). 

For preparative purposes, a Lewis acid such as AICI3 or FeCl3 is often used to catalyze chlorination. Chlorination of benzene by AICI3 is overall third-order. ... 

Since the mass absorption coefficient of hydrogen changes very little with wavelength, its value (0.435) may be taken from the literature. For carbon, 0.567, which was obtained from the measured kf for benzene by allowing for the absorption due to hydrogen, will serve. For chlorine, the rounded value na = 12 was chosen on the basis of the literature, which gives 11.6 at 0.71 A.13 With the numerical values inserted, Equation 3-8 becomes... 

Phthalaldehyde Acid (16, 68) By chlorination of phthalide, followe by hydrolysis with boiling water and crystallization from benzene. Austin and Bousquet, U. S. pat. 2,047,946 [C. A. 30,6on (rg36)]. 

Despite the relative simplicity of the kinetics of molecular chlorination, there has so far been only one measurement of the rate coefficient with a heterocyclic compound and the need for more work in this area is indicated. Marino265 found that chlorination of thiophene by chlorine in acetic acid at 25 °C gave the second-order rate coefficient of 10.0 1.5, so that thiophene is 1.7 x 109 times as reactive as benzene in this reaction and this large rate spread is clearly consistent with the neutral and hence relatively unreactive electrophile. 

The rates of chlorination of benzene, biphenyl, and diphenylmethane by chlorine acetate in 98 % aqueous acetic acid at 25 °C have also been determined and the second-order rate coefficients are 0.00118, 0.0364, and 0.0311, respective-]y209 , 270 jjje varjation in rate with change in water content of the acetic acid was the same as that previously observed209 for toluene, and thus in ca. 75 % aqueous acid the coefficients were 0.00073, 0.027 and 0.0241 however, elsewhere in ref. 209a a 4-fold decrease in rate coefficient for diphenylmethane was claimed to accompany the same increase in water content of the medium. 

Example 1.2 Suppose it is desired to make 1,4-dimethyl-2,3-dichloro-benzene by the direct chlorination of pura-xylene. The desired reaction is... 

The diaminobenzenes are made from benzene by a combination chlorination-nitration route although para-phenylene diamine is also made directly from aniline. orr/to-Phenylene diamine is widely used for the preparation of biologically active compounds such as fungicides and veterinarian medicines. The mera-diamine is used in fire-retardant textile fibers ( Nomex ) while the / ara-diamine finds use in high-strength textile fibers used for bullet-proof vests, sails, army helmets, and other types of fiber-reinforced plastics ( Kevlar ). 

During the course of an attempted recrystallization of this complex from benzene containing chlorinated impurities the solution was exposed to light. The crystalline compound that formed from this solution was identified by X-ray crystallography as Mo(TPP)(Ph)Cl (Fig. 3). The complex contains Irons phenyl and chloro ligands, and the Mo—C and Mo—N4 plane distances are 2.241(1) and 0.125 A, respectively. A systematic synthesis of the complex could not subsequently be developed and consequently other spectroscopic and magnetic data were not collected. 

DMSO or other sulfoxides react with trimethylchlorosilanes (TCS) 14 or trimefhylsilyl bromide 16, via 789, to give the Sila-Pummerer product 1275. Rearrangement of 789 and further reaction with TCS 14 affords, with elimination of HMDSO 7 and via 1276 and 1277, methanesulfenyl chloride 1278, which is also accessible by chlorination of dimethyldisulfide, by treatment of DMSO with Me2SiCl2 48, with formation of silicon oil 56, or by reaction of DMSO with oxalyl chloride, whereupon CO and CO2 is evolved (cf also Section 8.2.2). On heating equimolar amounts of primary or secondary alcohols with DMSO and TCS 14 in benzene, formaldehyde acetals are formed in 76-96% yield [67]. Thus reaction of -butanol with DMSO and TCS 14 gives, via intermediate 1275 and the mixed acetal 1279, formaldehyde di-n-butyl acetal 1280 in 81% yield and methyl mercaptan (Scheme 8.26). Most importantly, use of DMSO-Dg furnishes acetals in which the 0,0 -methylene group is deuter-ated. Benzyl alcohol, however, affords, under these reaction conditions, 93% diben-zyl ether 1817 and no acetal [67]. 

Attention has been directed to the dechlorination of polychlorinated benzenes by strains that use them as an energy source by dehalorespiration. Investigations using Dahalococcoides sp. strain CBDBl have shown its ability to dechlorinate congeners with three or more chlorine substituents (Holscher et al. 2003). Although there are minor pathways, the major one for hexachlorobenzene was successive reductive dechlorination to pentachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4-trichlorobenzene, and 1,4-dichlorobenzene (Jayachandran et al. 2003). The electron transport system has been examined by the use of specific inhibitors. lonophores had no effect on dechlorination, whereas the ATP-synthase inhibitor A,A -dicyclohexylcarbodiimide (DCCD) was strongly inhibitory (Jayachandran et al. 2004). 

In each case, the polymer is obtained as a white elastomer of high molecular weight (>106 in some experiments). Each of these polymers is soluble in benzene, in chlorinated hydrocarbons and in dipolar aprotic solvents. Figure 1 shows the kinetics of chloride substitution by tetra-n-butylammonium benzoate in N,N-dimethylacetamide at 50°C, for PECH and for the polymers of 2a-c. Under these conditions, each of the higher homologues is about equally reactive, and all are converted to the benzoate more rapidly than PECH. Each... 

Monochlorobenzene is produced by the reaction of benzene with chlorine. A mixture of monochlorobenzene and dichlorobenzene is produced, with a small amount of trichlorobenzene. Hydrogen chloride is produced as a byproduct. Benzene is fed to the reactor in excess to promote the production of monochlorobenzene. 

Chlorobenzene is manufactured by the reaction between benzene and chlorine. A number of secondary reactions occur to form undesired by products. 

Iodine can, however, be displaced cleanly with bromine<150) and with chlorine if iodine monochloride or sulfuryl chloride and benzoyl peroxide are used as chlorinating agents.reactivity ratios for the displacement of bromine by chlorine from substituted bromo-benzenes have been found to be in the order p-phenyl > o-methoxy > p-chloro > un-... 

Dichloroacetophenone has been prepared by chlorination of acetophenone with and without aluminum chloride 1 by action of dichloroacetyl chloride upon benzene and aluminum chloride 1 by action of hypochlorous acid upon phenylacetylene 2 by heating trichloromethylphenylcarbinol 3 and by chlorination of phenylacetylene in alcohol.4... 

Aromatic aminosulfonic acids are synthesized by a sequence of important industrial processes, including sulfonation of benzene. This is followed, wherever necessary, by chlorination, nitration, and reduction, or by aniline sulfonation, possibly involving subsequent baking [7,8]. 

The second structural property described by the 4ypc index is the substitution pattern on the benzene ring. The value of the 4ypc index increases sharply with the degree of substitution, while in the isomeric classes of substituted benzenes it increases with the proximity of substituents. Thus, this structural parameter has also been found to be very useful in describing activities and properties of polysubstituted benzenes [103], chlorinated benzenes [279], and polychlorinated biphenyls [286]. 

Beurskens, J.E.M., Dekker, C.G.C., van der Heuvel, H., Swart. M., de Wolf, and Dolfing, J. Dehalogenation of chlorinated benzenes by an anaerobic microbial consortium that selectively mediates the thermodynamic and most favorable reactions,... 

Rimington GE, Ziegler G. 1963. Experimental porphyria in rats induced by chlorinated benzenes. Biochem Pharmacol 12 1387-1397. 

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