Benzal chloride, hydrolysis

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. 

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). 

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. 

Chloride Hydrolysis Investigated in Micro Reactors Organic synthesis 2 [OS 1] Hydrolysis of benzal chloride... 

Figure 4.38 Increase in benzaldehyde yield with increase in reaction temperature by performing benzal chloride hydrolysis in a slit-shaped interdigital micro mixer [46].

Figure 4.39 Comparison of benzal chloride hydrolysis performed in a slit-shaped micro mixer and in a mixing tee [46],...

OS 2] [R 20] [P Ij The feasibility of the micro channel hydrolysis of 4-fluorobenzal chloride was shown [46]. A maximum yield of about 50% at 100% conversion was reached (20-70 °C). Higher yields at low conversions were found compared with benzal chloride hydrolysis. 

The first synthesis of a cyclopropenone was reported in 1959 by Breslowls who achieved the preparation of diphenyl cyclopropenone (11) by reacting phenyl ketene dimethylacetal with benzal chloride/K-tert.-butoxide. The phenyl chloro carbene primarily generated adds to the electron-rich ketene acetal double bond to form the chlorocyclopropanone ketal 9, which undergoes 0-elimination of HC1 to diphenyl cyclopropenone ketal 10. Final hydrolysis yields 11 as a well-defined compound which is stable up to the melting point (120—121 °C). 

Side chain chlorination of toluene gives benzal chloride, which on hydrolysis gives benzaldehyde. This is a commercial method of manufacture of benzaldehyde. 

Benzaldehyde is prepared by hydrolysis of benzal chloride, for example in acidic media in the presence of a catalyst such as ferric chloride, or in alkaline media with aqueous sodium carbonate. Part of the commercially available benzaldehyde originates from a technical process for phenol. In this process, benzaldehyde is a byproduct in the oxidation, with air, of toluene to benzoic acid. 

Benzaldehyde. Annual production of benzaldehyde requires ca 6,500-10.000 t (2—3 < 10 gal) of toluene. It is produced mainly as by product during oxidation of toluene to benzoic acid, bin some is produced by hydrolysis of benzal chloride. The main use of benzaldehyde is as a chemical intermediate for production of fine chemicals used for food flavoring, pharmaceuticals, herbicides, and dyestuffs. 

The process is used on a commercial scale to prepare benzaldehyde by heating benzal chloride with an aqueous suspension of chalk or milk of lime under pressure. Water is sufficient to bring about hydrolysis, the alkali is added to remove the hydrogen chloride formed, and so prevent the reverse reaction taking place. In place of an alkali, a trace of iron powder can be used the reaction here takes a slightly different course, only 1 mol. of water being required for 1 mol. of the dichloride. 

Most of the technical grade is made by direct vapor-phase oxidation of toluene, although some is made by chlorinating toluene to benzal chloride, followed by alkaline or acid hydrolysis. For perfume and flavoring use, the refined, chlorine-free grade is required, which is economically produced by the direct vapor-phase oxidation of toluene with air at 500°C. 

Electroreduction of benzal chloride in the presence of carbon dioxide in DMF solvent gives very low yield of phenylacetic acid (131) (equation 70). The study suggests that the monoanion adds C02 to yield intermediate a-chlorophenylacetate which forms a-lactone. The acid is obtained following hydrolysis of the a-lactone by adventitious moisture in the DMF as shown in Scheme 910. 

Hydrolysis of 2,6-dichlorobenzal chloride is much more difficult than that of benzal chloride itself. In contrast to the latter, 2,6-dichloro-benzal chloride is not hydrolyzed either by water and iron or by calcium or potassium hydroxide, even under pressure at 150°C. The hydrolysis to the desired aldehyde is effected with concentrated sulfuric acid, although a considerable portion of the product is resinified in the process. 

Benzaldehyde is prepared by the hydrolysis of (dichloromethyl)benzene (benzal chloride) in either aqueous acid or aqueous alkali and by the oxidation of toluene with chromium trioxide in acetic anhydride (Scheme 6.3). In the latter synthesis, as the benzaldehyde is formed, it is converted into its diacetate by the acetic anhydride, so preventing further oxidation subsequent hydrolysis generates the aldehyde group. The benzaldehyde has thus been protected from oxidation. Benzyl alcohol can... 

Introduction. Polyhalogen compounds may be divided for the purpose of study into two groups. The first group includes compounds that have two or more halogen atoms on the same carbon atom, as for example, chloroform, CHCU, benzal chloride, CeHsCHCh, and 1,1-dichloroethane, CH3CHCI2. Such compounds on hydrolysis yield carbonyl and carboxyl compounds ... 

Benzaldehyde is prepared by the hydrolysis of (dichloromethyl)benzene (benzal chloride) in either aqueous acid or aqueous alkali and by the oxidation of toluene with chromium trioxide in acetic anhydride (Scheme... 

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... 

Irradiation of phenol in chloroform gave, after work up, o- and p-hydroxybenzaldehyde, while irradiation of N,N-diethylaniline gave o- and p-diethylaminobenzaldehyde. The aldehydes are thought to have been formed by hydrolysis of the corresponding benzal chlorides, and these to have been formed in reactions of the dichloro-methyl radical ( CHC12) whose origin, of course, is the anion CHCI3-(Hirao and Yonemitsu, 1972). 

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. 

Aldehydes and ketones, which are produced by different methods and starting materials, are important carbonyl compounds that are widely used as such and for further processing [1], For example, cyclohexanone can be prepared upon cyclohexane oxidation, dehydrogenation of cyclohexanol at high temperature, or via catalytic oxidation of cyclohexanol under milder conditions. Acetophenone can be produced by the Hock process or be obtained via ethylbenzene oxidation with dioxygen, whereas benzaldehyde is produced industrially by toluene oxidation or by hydrolysis of benzal chloride in the presence of different acids and/or metal salts (i.e., tin(II), tin(IV), iron, or zinc chlorides) [1],... 

Benzotrichloride is used mainly to produce benzoyl chloride by partial hydrolysis. Photochemical chlorination is widely used for the production. In order to avoid excessive chlorination and the formation of ring-chlorinated substances, cascades of six to ten reactors are applied in continuous processes. Like benzal chloride, benzotrichloride is toxic and suspected to have a carcinogenic potential. 

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