Benzyl chloride chlorination of toluene

Method 1. Fit a 500-ml. three-necked flask with a thermometer (the bulb of which is within 2 cm. of the bottom), and inlet tube extending to the bottom of the flask, and a double surface condenser. Use old  

Transfer the reaction mixture to a Claisen flask and distil under atmospheric pressure until the temperature reaches 135-140° (3). Distil the residue under diminished pressure and collect the benzyl chloride at 64-69°/12 mm. The latter upon redistillation boils largely at 63- 65°/12 mm. The yield of benzyl chloride is about 100 g. 

Method 2. In a 500-ml. round-bottomed flask, fitted with an efficient reflux condenser, place 92 g. (106 ml.) of toluene, 68 g. (41 ml.) of redistilled sulphuryl chloride and 1 g. of dibenzoyl peroxide (Section IV,196). Reflux gently, when a vigorous reaction takes place the reaction is complete in 30 minutes. Isolate the benzyl chloride as described in Method 1. The yield is 50 g. 

Benzal chloride (benzylidene chloride). Use 100 g. of toluene and continue the passage of chlorine until the increase in weight of the flask and contents is 74 g. or, alternatively, until the temperature rises to 187°. Collect the benzal chloride at 204-208° or at 104 105°/30 mm. Pure benzylidene chloride has b.p. 206°. 

Into a 1-litre three-necked flask, equipped with a reflux (double surface) condenser, a mechanical stirrer (preferably of the Hershberg type, Fig. II, 7, 8) and a gas lead-in tube extending to near the bottom of the flask, pla 200 g. (227 ml.) of dry benzene, 20 g. of paraformaldehyde (1) and 20 g. of finely-pulverised, anhydrous zinc chloride. Support the flask on a water bath so arranged that the level of the water in it is about 

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Chlorination reactions are also highly exothermic and the use of microflow systems is quite effective for conducting the reaction in a controlled manner. Various chlorination reactions including chlorination of toluene derivative to obtain benzyl chlorides, chlorination of acetic acid to obtain chloroacetic acid, and radical chlorination of alkanes using microflow systems have been reported. 

Benzyl Chloride. Benzyl chloride is manufactured by high temperature free-radical chlorination of toluene. The yield of benzyl chloride is maximized by use of excess toluene in the feed. More than half of the benzyl chloride produced is converted by butyl benzyl phthalate by reaction with monosodium butyl phthalate. The remainder is hydrolyzed to benzyl alcohol, which is converted to ahphatic esters for use in soaps, perfume, and davors. Benzyl salicylate is used as a sunscreen in lotions and creams. By-product benzal chloride can be converted to benzaldehyde, which is also produced directiy by oxidation of toluene and as a by-product during formation of benzoic acid. By-product ben zotrichl oride is not hydrolyzed to make benzoic acid but is allowed to react with benzoic acid to yield benzoyl chloride. 

The only industrially important processes for the manufacturing of synthetic benzaldehyde involve the hydrolysis of benzal chloride [98-87-3] and the air oxidation of toluene. The hydrolysis of benzal chloride, which is produced by the side-chain chlorination of toluene, is the older of the two processes. It is no longer utilized ia the United States. Other processes, including the oxidation of benzyl alcohol, the reduction of benzoyl chloride, and the reaction of carbon monoxide and benzene, have been utilized ia the past, but they no longer have any iadustrial appHcation. 

In the past benzal and benzyl chlorides were co-produced for the manufacture of benzaldehyde and benzyl alcohol, but today the vast majority of the benzaldehyde produced from benzal chloride is that which is made from recovered (by-product) material. For an historical article regarding the chlorination of toluene and the subsequent production of benzaldehyde, benzyl alcohol, and benzoic acid, see reference 4. 

Continuous chlorination of benzene at 30—50°C in the presence of a Lewis acid typically yields 85% monochlorobenzene. Temperatures in the range of 150—190°C favor production of the dichlorobenzene products. The para isomer is produced in a ratio of 2—3 to 1 of the ortho isomer. Other methods of aromatic ring chlorination include use of a mixture of hydrogen chloride and air in the presence of a copper—salt catalyst, or sulfuryl chloride in the presence of aluminum chloride at ambient temperatures. Free-radical chlorination of toluene successively yields benzyl chloride, benzal chloride, and benzotrichloride. Related chlorination agents include sulfuryl chloride, tert-huty hypochlorite, and /V-ch1orosuccinimide which yield benzyl chloride under the influence of light, heat, or radical initiators. 

Benzyl chloride is manufactured by the thermal or photochemical chlorination of toluene at 65—100°C (37). At lower temperatures the amount of ring-chlorinated by-products is increased. The chlorination is usually carried to no more than about 50% toluene conversion in order to minimize the amount of benzal chloride formed. Overall yield based on toluene is more than 90%. Various materials, including phosphoms pentachloride, have been reported to catalyze the side-chain chlorination. These compounds and others such as amides also reduce ring chlorination by complexing metallic impurities (38). 

Benzotrichloride is produced from total side-chain chlorination of toluene or of residual products from benzyl chloride production. In Western Europe, Bayer has the largest capacity (14,000 t/yr), and there are only two significant producers in the United States Occidental Chemical in Niagara EaUs, New York (20,000 t/yr), and Velsicol Chemical (11,000 t/yr). Total capacity in the western world is 68,000 t/yr and production of benzotrichloride in 1988 was estimated at 31,500 t. 

The chlorination of toluene by substituting the methyl hydrogens is a free radical reaction. A mixture of three chlorides (benzyl chloride, ben-zal chloride and benzotrichloride) results. 

No catalyst) Benzyl chloride Benzal chloride Benzotrichloride Rapid side-chain chlorination of toluene proceeds in the dark with sulphuryl chloride in the presence of dibenzoyl peroxide (O 001-0 005 mol per mol of SOjClj) as catalyst ... 

Side-Chain Chlorination of Toluene. Benzyl chloride, used mainly in the manufacture of plasticizers, may be prepared by the thermal or photochemical chlorination of toluene.191,192 In the thermal process chlorine is passed through toluene at 65-100°C. To minimize the formation of benzal chloride and benzotrichloride, the conversion is limited to about 50%. Since the density of the reaction mixture increases linearly with the formation of benzyl chloride,145 measurement of density is used to monitor the progress of the reaction. The overall yield based on toluene is about 90%, and the maximum conversion to benzyl chloride is above 70%. Higher yields in photochemical chlorination may be achieved. 

Benzyl chloride ix used in the production of benzaldehyde and butyl benzyl phthalute. It is produced by the chlorination of toluene... 

Benzyl chloride is prepared by free-radical chlorination of toluene. 

Polyhalide salts are prepared in situ in the bromination of less reactive aromatic substrates. Thus, tetra- -butylammonium bromide(TBAB) functions as a catalyst in the bromination of benzene, toluene and even benzyl bromides and a-bromoethylbenzene537 (both tend to polymerize in presence of normal Friedel-Crafts catalysts). Tetra-ethylammonium chloride in CH2Cl2/methanol catalyzes the bromination of anilines538. Improved selectivity is found in the chlorination of toluene catalyzed by onium chloride salts alone or combined with SnCl4539. 

Another reaction which can be brought about by PCI5 is the conversion of aldehydes and ketones into the corresponding geminal dichlorides and this is illustrated in Protocol 7 by the conversion of terephthalaldehyde 36 into the tetrachloride 37. Unusually for a reaction using PCI5, no HC1 is evolved here and the product is sufficiently unreactive to be isolated using an aqueous work-up. It should be noted that chlorination of aromatic aldehydes in this way is the method of choice for synthesis of benzylidene chlorides since the products obtained from the alternative chlorination of toluenes are always contaminated by the benzyl chlorides and benzotrichlorides. 

In the industrial manufacture of bromobenzyl cyanide it is preferable to commence with benzyl chloride rather than benzyl bromide. This is easily obtained by the chlorination of toluene under the influence of sunlight (see p. 129) or by the aid of a mercury vapour lamp. ... 

Brombenzyl cyanide was first prepared by Riener in 1881 by hrom-inating phenyl cyanide, and its manufacture in industry was commenced n 1914. Industrially, brombenzyl cyanide is prepared in three steals, as follows (1) chlorination of toluene to form benzyl chloride (2) the conversion of benzyl chloride to benzyl cyanide by the action of sodium cyanide in alcoholic solution (3) the bromination of the benzyl cyanide with bromine vapor in the presence of sunlight. 

Side-chain chlorination of toluene can yield successively the mono-, di-, and trichloro compounds. These are known as benzyl chloride benzol chloride, and... 

Halogenation of hydrocarbons. Walling found /-butyl hypochlorite useful for light- or radical-induced chain chlorination of toluene. Thus, in the presence of azobisisobutyronitrile as initiator, the reaction with toluene at 40° affords benzyl chloride (84%), /-butanol (97%), and 1-3% each of chlorololuenes, methyl chloride, and acetone. 

The photochemical chlorination of toluene-2,4-diisocyanate has also been reported (Scheme 8.3). A falling-film microflow reactor is used with irradiation of gaseous chlorine, through a quartz window, enabling the in situ generation of chlorine radicals. The optimal residence time is 9 s at 130 °C, and benzyl chloride-2,4-diisocyanate is produced in 81.0% yield. 

Chlorination of toluene with CBT at elevated temperature proceeds on the methyl group as well as on the ring. Together with benzyl chloride (40-50%) and a mixture of chlorotoluenes (8-20%) 1-benzylbenzotriazole (7%), benzotriazole (65%), and its hydrochloride (10%) are formed [69JCS(C)1478 72MI2], In this case radical as well as electrophilic halogenation takes place. 

Chlorination of toluene under radical conditions (either through the use of an initiator or by photolysis) gives a mixture of mono-, di- and trichlorotoluene. In practice in the perfumery industry, the reaction is run with an excess of toluene present, which means that benzyl chloride is the major product. A little benzal chloride is produced and can be separated and hydrolysed to give benzaldehyde. The major use of benzyl chloride is in the production of benzyl alcohol and its esters. The alcohol is produced by hydrolysis of the chloride. The esters can be prepared by esterification of the alcohol, but it is better economically to prepare... 

Ledwith and Russell (1974b) have found that chlorination of benzene, toluene and other aromatic molecules is easily achieved in aqueous acetonitrile containing sodium peroxydisulfate and copper(II) chloride. Toluene, for example, gives no benzyl chloride but a mixture of chlorotoluenes (58% o-, 4% m-, and 38% p-) consistent with the spin distribution in the toluene cation radical. The amount of copper chloride used can be catalytic provided another source of chloride ion (LiCl) is added. Reaction is attributed to the very fast transfer of chlorine atom from copper(II) chloride to the cation radical (132) the metal halide is thus regarded as a trap for the aromatic cation radical. In the absence of copper(II) chloride, reactions of toluene with peroxydisulfate ion and chloride ion give... 

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