Synthesis of benzal chloride

Preparation of benzal chloride

Preparation of benzal chloride by chlorination of toluene with chlorine

Preparation of benzal chloride

Preparation of benzal chloride

Glass apparatus for the preparation of benzal chloride is shown below. The chlorination is carried out in a one-necked flask equipped with a thermometer, a chlorine inlet tube 2 (diameter about 7 mm) and a reflux condenser. End of the thermometer should be immersed in the liquid at a distance of 2 cm from the bottom of the flask. The inlet tube 2 for the introduction of chlorine should reach almost to the bottom of the flask; the second end of the tube is connected through a Woolfe’s flask 3, containing concentrated sulfuric acid, and 4 normal wash bottle, filled to half of the sulfuric acid for the washing of chlorine. The end of the reflux condenser connects U-shaped tube filled with calcium chloride, with an absorbent 5 for hydrogen chloride.

A glass apparatus for the preparation of benzal chloride

A glass apparatus for the preparation of benzal chloride

In the reaction flask 50 g (58 ml, 0.54 mol) toluene and a few pieces of porous porcelain were placed. The flask is weighed heated in a sand bath (weigh the reaction vessel before the reaction is necessary for controlling the amount of chlorine which is absorbed during the reaction). When the toluene starts to boils (at 110 °), the chlorine gas is introduced. The current of chlorine gas must be rapid, but not strong enough for chlorine to take out the vaporized droplets of toluene. The temperature of the sand bath must be maintained so that the reaction mixture is in a state of constant boiling. During the chlorination reaction the temperature rises and increases the weight of the flask (on a sunny day, or by applying light quartz lamp reaction occurs within 3-5 hours. Poor lighting increases the duration of the reaction). Once the temperature reaches 187 ° C and increasing the weight of the flask by 37 g (0.52 moles chlorine) the reaction is finished. The reaction product was distilled by collecting the fraction with boiling point 204-208° C. Pure benzal chloride boils at 206° C. Yield 73 g (84% of theory). Benzal chloride distilled at ambient pressure, appears slightly colored due to the presence of decomposition products. With careful distillation in vacuum very pure product may be obtained.

Benzal chloride can also be obtained by reacting benzaldehyde with phosphorus pentachloride or thionyl chloride.

Препаративная органическая химия, Вульфсон Н.С., 188-189, 1959 (Preparative organic chemistry, Wolfson N. S.,  188-189, 1959)

Preparation of benzal chloride

Preparation of benzal chloride

To prepare the benzal chloride a molar ratio of toluene to sulfuryl chloride of 1:2 is used. After the addition of 0.002 mole of benzoyl peroxide or, still better, azo-bis-isobutyronitrile (referred to 1 mole of sulfuryl chloride) the toluene and the sulfuryl chloride are heated to the boil in a round-bottomed flask with a very efficient reflux condenser and a calcium chloride tube. At intervals of 1 hr, the same amount of chain initiator is added. The reaction is complete in 8-10 hours and  when no further evolution of gas can be observed. The mixture is allowed to cool and is washed with water and it is then dried with magnesium sulfate and fractionated through a 20-cm Vigreux column yielding 75% of benzal chloride, b.p. 86°C/14mm; n20/D 1.5503.

Organicum. Practical Handbook of Organic Chemistry, by Heinz Becker, Werner Berger and Günter Domschke, Addison-Wesley Pub. Co, 170, (1973)

Preparation of benzal chloride from benzaldehyde

Preparation of benzal chloride from benzaldehyde

Thionyl chloride is added gradually, with cooling, to benzaldehyde. When evolution of sulfur dioxide ceases, the solution is shaken with water, and the oil that separates is taken up in ether and shaken with sodium bisulfite solution to remove unchanged benzaldehyde; after filtration, the ether is distilled off; distillation of the residue affords pure benzylidene dichloride in good yield.

F. Loth, A. Michaelis, Ber. Deut. Chem. Ges., 27, 2548 (1894).





InChI Key


Canonical SMILES


MeSH Synonyms

benzal chloride

Depositor-Supplied Synonyms

Benzal chloride, (DICHLOROMETHYL)BENZENE, alpha,alpha-Dichlorotoluene, Benzene, (dichloromethyl)-, Benzyl dichloride, Benzylidene chloride, Dichlorophenylmethane, Benzylene chloride, Chlorobenzal, 98-87-3, Benzylidene dichloride, Chlorure de benzylidene, Benzene, dichloromethyl-, RCRA waste number U017, Dichloromethylbenzene, DICHLOROTOLUENE, NSC 7915, RCRA waste no. U017, CCRIS 959, Toluene, alpha,alpha-dichloro-, .alpha.,.alpha.-Dichlorotoluene, CHEBI:82273, HSDB 5322, Chlorure de benzylidene [French], Cloruro de bencilideno [Spanish], CAHQGWAXKLQREW-UHFFFAOYSA-N, UNII-222447TR16, EINECS 202-709-2, Toluene, .alpha.,.alpha.-dichloro-, UN1886, BRN 1099407, AI3-28597, DSSTox_CID_5014, DSSTox_RID_77628, DSSTox_GSID_25014, 29797-40-8, CAS-98-87-3, chlorobenzyl chloride, BENZALCHLORIDE, Cloruro de bencilideno, WLN: GYGR, AC1L1OPA, AC1Q3H2Q, SCHEMBL28353, 251046_ALDRICH, .alpha.,.alpha.-Dichlortoluene, CHEMBL1412576, NSC7915, LTBB001581, ALPHA,ALPHA-DICHLORO-TOLUENE, NSC-7915, EINECS 249-854-8, Tox21_201313, Tox21_300171, AR-1G0262, AKOS015902605, LS-2050, Toluene, alpha,alpha-dichloro- (8CI), UN 1886, NCGC00091362-01, NCGC00091362-02, NCGC00091362-03, NCGC00254144-01, NCGC00258865-01, Benzylidene chloride [UN1886] [Poison], M012, Benzylidene chloride [UN1886] [Poison], 222447TR16, B1414, D0418, C19165, 4-05-00-00817 (Beilstein Handbook Reference), I14-20068, InChI=1/C7H6Cl2/c8-7(9)6-4-2-1-3-5-6/h1-5,7, 37808-21-2

Removed Synonyms

|A,|A-Dichlorotoluene, |A,|A-Dichlorobenzenea, Toluene,.alpha.-dichloro-, CID7411, C032732, 6292-07-5

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