Benzal chloride

The production of benzal chloride is relatively insignificant in comparison with that of benzyl chloride. Benzal chloride is mainly used to make benzaldehyde, obtained by alkaline hydrolysis (Na2C03) or in an acidic medium (ZnCl2) at 120 to 130 °C, Benzaldehyde however can also be recovered as a byproduct of the oxidation of toluene to benzoic acid, occurring in quantities of between 5 and 8% this route leads to benzaldehyde which is distinguished by the lack of chlorine impurities. The main uses for benzaldehyde are the production of benzyl alcohol (see Chapter 6.3.1.1), chloramphenicol, 2-phenylglydne and cinnamaldehyde. 

The antibiotic chloramphenicol, which is mainly used in veterinary medicine, is produced by the Boehringer Mannheim process from dnnamic alcohol, which in turn is obtained from benzaldehyde through aldol condensation with acetaldehyde and reduction of the intermediate cinnamaldehyde. 

2-Phenylglycine is produced as a DL-amino-acid mixture from benzaldehyde, sodium cyanide and ammonium chloride. The D-form of 2-phenylglycine is of particular importance and is used in the manufacture of a wide range of semi-synthetic penicillins, such as ampicillin, which is produced worldwide in a quantity of approx. 3,0001. 

Cinnamaldehyde is obtained by the aldol condensation of acetaldehyde with benzaldehyde when reacted with long chain n-aldehydes (Cy/C X it is used to produce fragrances and perfumes. 

Self-condensation of benzaldehyde produces benzoin, which is used as a photoinitiator for UV hardening of paints. Benzil, which is obtained by oxidation of benzoin, has the same application. 

Vapor irritates respiratory system and eyes. Liquid irritates eyes and skin. Both may cause conjunctivitis. Swallowing would cause internal damage. Avoid breathing vapor. Avoid contact with skin and eyes.2 

Instruct others to keep a safe distance. Wear breathing apparatus, laboratory coat, eye protection, and nitrile rubber gloves. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Scoop into an appropriate container and package for disposal by burning.3-5 Area of spillage should be washed thoroughly with soap and water.2 

Package Lots. Place in a separate labeled container for recycling or disposal by burning. Dissolve the compound in a flammable solvent and spray into furnace with afterburner 

Small Quantities. Wear nitrile rubber gloves, laboratory coat, and eye protection. Work in the fume hood. Place 7.9 g (0.12 mol) of 85% potassium hydroxide pellets into a 100-mL, three-necked, round-bottom flask equipped with stirrer, water-cooled condenser, dropping funnel, and heating mantle or steam bath. With brisk stirring, rapidly add 31.5 mL of 95% ethanol. The potassium hydroxide dissolves within a few minutes, causing the temperature of the solution to rise to about 55°C. Heat the solution to gentle reflux 

Reactions for Spillage and Waste Disposal C H-CCljH + 2KOH CfiH-COOH + C6HsCH OH + 2KG + H20 

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With excess of sulphuryl chloride, benzal chloride is formed, but chlorination does not proceed beyond this stage. 

Benzal chloride (benzylidene chloride). Use 100 g. of toluene and continue the passage of chlorine imtil 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°,... 

Place 45 g. (43 ml.) of benzal chloride (Section IV,22), 250 ml. of water and 75 g. of precipitated calcium carbonate (1) in a 500 ml. round-bottomed flask fltted with a reflux condenser, and heat the mixture for 4 hours in an oil bath maintained at 130°. It is advantageous to pass a current of carbon dioxide through the apparatus. Filter off the calcium salts, and distil the filtrate in steam (Fig. II, 40, 1) until no more oil passes over (2). Separate the benzaldehyde from the steam distillate by two extractions with small volumes of ether, distil off most of the ether on a water bath, and transfer the residual benzaldehyde to a wide-mouthed bottle or flask. Add excess of a concentrated solution of sodium bisulphite in portions with stirring or shaking stopper the vessel and shake vigorously until the odour of benzaldehyde can no longer be detected. Filter the paste of the benzaldehyde bisulphite compound at the pump... 

The common names of (di chloromethyl)benzene and (trichloromethyl)benzene are benzal chloride and benzo trichloride respectively... 

Bentonite seal Benuron Benzadrine Benzal chloride... 

Cm.OROCARBONSANDCm.OROHYDROCARBONS - BENZYL Cm ORIDE, BENZAL Cm ORIDE AND BENZOTRICm ORIDE] (Vol 6) Benzal chloride [98-87-3]... 

Although 4-hydroxybenzaldehyde can be made by the saligenin route, it has been made historically by the Reimer-Tiemann process, which also produces sahcylaldehyde (64). Treatment of phenol with chloroform and aqueous sodium hydroxide results in the formation of benzal chlorides, which are rapidly hydrolyzed by the alkaline medium into aldehydes. Acidification of the phenoxides results in the formation of the final products, sahcylaldehyde and 4-hydroxybenzaldehyde. The ratio of ortho and para isomers is flexible and can be controlled within certain limits. The overall reaction scheme is shown in Figure 1. Product separation is accomphshed by distillation, but this process leads to environmental problems because of the quantities of sodium chloride produced. 

Substitution Reactions on the Methyl Group. The reactions that give substitution on the methyl group are generally high temperature and free-radical reactions. Thus, chlorination at ca 100°C, or in the presence of ultraviolet light and other free-radical initiators, successively gives benzyl chloride, benzal chloride, and benzotrichloride. 

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. 

Mol reactant in pdt T oluene Benzyl chloride Benzal chloride B enz o trichlo ride... 

Nearly all of the benzyl chloride [100-44-7], henzal chloride [98-87-3], and hen zotrichl oride /P< -(97-i manufactured is converted to other chemical intermediates or products by reactions involving the chlorine substituents of the side chain. Each of the compounds has a single primary use that consumes a large portion of the compound produced. Benzyl chloride is utilized in the manufacture of benzyl butyl phthalate, a vinyl resin plasticizer benzal chloride is hydrolyzed to benzaldehyde hen zotrichl oride is converted to benzoyl chloride. Benzyl chloride is also hydrolyzed to benzyl alcohol, which is used in the photographic industry, in perfumes (as esters), and in peptide synthesis by conversion to benzyl chloroformate [501-53-1] (see Benzyl ALCOHOL AND p-PHENETHYL ALCOHOL CARBONIC AND CARBONOCm ORIDIC ESTERS). 

Table 2. Physical Properties of Benzyl chloride, Benzal Chloride, and Benzotrichloride...

Benzal chloride [(dichloromethyl)benzene, a,a-dichlorotoluene, benzylidene chloride], C H CHCl, is a colorless Hquid with a pungent, aromatic odor. Benzal chloride is insoluble in water at room temperature but is miscible with most organic solvents. 

Binary azeotropic systems are reported for all three derivatives (9). The solubiHties of benzyl chloride, benzal chloride, and ben zotricbl oride in water have been calculated by a method devised for compounds with significant hydrolysis rates (10). 

Benzal chloride is hydrolyzed to benzaldehyde under both acid and alkaline conditions. Typical conditions include reaction with steam in the presence of ferric chloride or a zinc phosphate catalyst (22) and reaction at 100°C with water containing an organic amine (23). Cinnamic acid in low yield is formed by heating benzal chloride and potassium acetate with an amine as catalyst (24). 

Aromatic Ring Reactions. In the presence of an iodine catalyst chlorination of benzyl chloride yields a mixture consisting mostly of the ortho and para compounds. With strong Lewis acid catalysts such as ferric chloride, chlorination is accompanied by self-condensation. Nitration of benzyl chloride with nitric acid in acetic anhydride gives an isomeric mixture containing about 33% ortho, 15% meta, and 52% para isomers (27) with benzal chloride, a mixture containing 23% ortho, 34% meta, and 43% para nitrobenzal chlorides is obtained. 

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). 

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). 

Benzyl chloride is classified by DOT as chemicals NOIBN, poisonous, corrosive and a hazardous substance (100 lbs-45.45 kg). Benzal chloride is classified as poisonous and a hazardous substance (5000 lbs-2270 kg). Benzotrichloride is classified under DOT regulation as a corrosive Hquid NOS and a hazardous substance (10 lbs-4.5 kg). The Freight Classification Chemical NOI appHes. It is shipped in lacquer-lined steel dmms and nickel-lined tank trailers. Benzal chloride is handled in a similar fashion. 

The side-chain chlorine contents of benzyl chloride, benzal chloride, and benzotrichlorides are determined by hydrolysis with methanolic sodium hydroxide followed by titration with silver nitrate. Total chlorine determination, including ring chlorine, is made by standard combustion methods (55). Several procedures for the gas chromatographic analysis of chlorotoluene mixtures have been described (56,57). Proton and nuclear magnetic resonance shifts, characteristic iafrared absorption bands, and principal mass spectral peaks have been summarized including sources of reference spectra (58). Procedures for measuring trace benzyl chloride ia air (59) and ia water (60) have been described. 

A gas chromatographic determination of benzotrichloride and related compounds ia the work environment, after adsorption on a polymeric adsorbant and desorption with CCl has been reported (61). Trace amounts of benzyl chloride, benzal chloride, and benzotrichloride ia environmental samples can be analyzed by Method 8120 of EPA ManualSW-846 with modifications (62). 

Vapors of both benzal chloride and benzotrichloride are strongly irritating and lacrimatory. Reported toxicides appear in Table 3. Also, for benzotnchlonde, the lowest pubflshed lethal dose (frog) is 2150 mg/kg (69) and the toxic dose level (inhalation rats) is 125 ppm/4 h (69). 

Nearly all of the benzal chloride produced is consumed in the manufacture of benzaldehyde. Benzaldehyde (qv) is used in the manufacture of perfume and flavor chemicals, dyes, and pharmaceuticals. The principal part of benzotrichloride production is used in the manufacture of benzoyl chloride (see Benzoic acid). Lesser amounts are consumed in the manufacture of benzotrifluoride, as a dyestuff intermediate, and in producing hydroxybenzophenone ultraviolet light stabilizers. Benzotrifluoride is an important intermediate in the manufacture of herbicides, pharmaceuticals, antimicrobial agents, and the lampreycide, 4-nitro-3-(trifluorometh5l)phenol [88-30-2]. 

Ring-Substituted Derivatives The ring-chlorinated derivatives of benzyl chloride, benzal chloride, and benzotrichloride are produced by the direct side-chain chlorination of the corresponding chlorinated toluenes or by one of several indirect routes if the required chlorotoluene is not readily available. Physical constants of the main ring-chlorinated derivatives of benzyl chloride, benzal chloride, and benzotrichloride are given in Table 4. 

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