Colorless to yellow powder or white crystalline solid. Pungent odor.
The preparation methods commonly used are the following.
Throw p-chlorotoluene into the reactor equipped with a UV lamp and put through chlorine gas at a reaction temperature of 60~100 ℃ for reaction. The molar ratio between the p-chlorotoluene amount and chlorine gas amount should be 1: 1.5. You can control the chlorine depth through GC approach. The reaction product contains chlorobenzyl chloride, p-chlorobenzal dichloride and 4-α, α, α-tetrachloro toluene. In case of large chlorine-depth, there is less amount of p-chlorobenzyl chloride while the amount of 4-α, α, α-tetrachloride toluene is about 8% with all the above three-component separated by distillation.
The mixture of 4-chlorobenzal dichloride and 4-α, α, α-tetrachloro-toluene can have hydrolysis reaction in the presence of catalysts such as FeCl3, ZnCl2, SnCl4, and metal oxides with the reaction temperature being 110~140 ℃. Add water for 4 hour of reaction, use GC approach for controlling the end of the reaction, and then go through vacuum distillation, under the protection of nitrogen gas, collect the fraction of 124 ℃/5.4kPa that is the product of p-chlorobenzaldehyde with the purity being over 99% and the yield being over 93% (calculated from 4-chlorobenzal dichloride).
The catalytic chlorination of Azobisisobutyronitrile:
Add p-chlorotoluene to the reactor and heated to 160 ℃, add azobisisobutyronitrile as the catalyst and put through chlorine gas for starting the reaction. Use GC approach for controlling the end point of the reaction. Take care that avoid generating 4-α, α, α-tetrachloride toluene and then apply vacuum distillation, collect the fraction of 116~126 ℃/3kPa with yield being 87%. The first fraction of p-chlorotoluene and p-chloro-benzyl chloride can be recycled for further application.
Add the 4-chlorobenzal dichloride obtained above into a reactor. Then add SnCl2 and adequate water for reaction upon reflux for 4h with the white crystal obtained after treatment being the product and the purity being 96% and the yield being 94%.
Methenamine hydrolysis approach
Add methenamine, water to the reactor, add the light chlorination reaction product of p-chlorotoluene, chlorobenzyl chloride and 4-chloro-benzal dichloride to the reaction flask and have reaction at 60~100 ℃ for 30~60min. The end point of the reaction is reached when the hydrolysis conversion ratio of benzyl chloride is 99%. After the post-treatment, we can obtain p-chlorobenzaldehyde with the purity being 99% and the yield of being 93.82%.
Manganese dioxide oxidation
Take p-chlorotoluene as raw materials, in the presence of sulfuric acid, take manganese dioxide as oxidizing agent for oxidation and then have steam distillation to obtain p-chlorobenzene formaldehyde which is the method of laboratory.
In addition to these methods, there are also some other methods including electrochemical synthesis and catalytic oxidation method. These methods are more difficult to be applied for industrialization. Some technology is not yet mature, pending further study. Regarding to hydrolysis of the 4-chlorobenzal chloride, we can also use 65% nitric acid for hydrolysis reaction at 90°C. The product purity is high and is up to 99% with the yield being 80%. In addition, in the presence of phosphorus trichloride, using chlorine gas for chlorination and further have hydrolysis reaction in the presence of sulfuric acid can also generate chlorobenzaldehyde but with lower yield and the older technology. For this reason, for the optimum technology for producing p-chlorobenzaldehyde, you can choose: use p-chlorotoluene as raw materials, have light chlorination, control the depth of chloride, then apply methenamine hydrolysis reaction. Through doing this, you need small investment; easy operation and can get high products quality and high yield.
4-Chlorobenzaldehyde is sensitive to exposure to air. 4-Chlorobenzaldehyde is also sensitive to light. REACTIVITY: 4-Chlorobenzaldehyde is incompatible with strong bases, strong oxidizers and strong reducing agents.
p-Chlorobenzaldehyde is also known as 4-chlorobenzaldehyde. It is colorless flake crystalline to pale yellow powder. The molecular weight is 140.57. Melting point is 47.5 ℃. Boiling point is 213~214 ℃. The relative density is 1.196 (61/4 ℃). The refractive index is 1.5552 (61 ℃). The flash point is 87 ℃. It is insoluble in water, easily soluble in alcohol, ether and benzene and soluble in acetone. It can be evaporated together with the steam. It can be used as the intermediates of medicine and dyes, for the manufacturing of chlormezanone, dapsone aminobutyric acid and so on. It can be obtained through the chlorination and hydrolysis of the chlorotoluene. It may also be produced through the oxidation of the p-chlorotoluene manganese dioxide oxidation. Furthermore, it can also be made by the air oxidation of the p-chlorotoluene.
It can be used for producing the plant growth regulator paclobutrazol: take p-dichlorobenzene formaldehyde and 2,2-dimethyl-3-butanone as raw material, have them react with each other in the solution of sodium hydroxide and tert-butanol, generating 1-(2,2-dimethyl-3-ketone-4-penten) p-chlorophenyl. In the ethyl acetate solution, take nickel as catalyst and have hydrogenation reaction at a high temperature to yield 1-(2,2-dimethyl-3-pentanone) chlorobenzene; have bromination reaction at carbon tetrachloride solution to generate 1-(2,2-dimethyl-4-bromo-3-pentanone) p-chlorophenyl, and further put into acetone solution to have reaction with 2,4-triazole, and finally generate paclobutrazol in the methanol solution of sodium boron hydride.
Baclofen can be used as the skeletal muscle relaxants and antispasmodic agent of spine. It is produced through the following process: first p-Chlorobenzaldehyde has condensation reaction with ethyl acetoacetate to generate chlorobenzene methylene-bis-ethyl acetoacetate. Then heat and hydrolyze to obtain p-chlorophenyl glutaric acid. Further use acetic anhydride for dehydration and cyclization to obtain p-chlorophenyl glutaric anhydride. Then use concentrated aqueous ammonia for amination to generate chlorophenyl glutaric acid imide, and finally have ring opening reaction and degradation to get it.
The above information is edited by the Chemicalbook of Dai Xiongfeng.
colourless to light yellow crystalline powder
Air & Water Reactions
4-Chlorobenzaldehyde is sensitive to exposure to air. Insoluble in water.
p-Chlorobenzaldehyde is not only the intermediate of tebuconazole fungicides, plant growth regulators uniconazole but also the intermediate of insecticide chlorfenapyr. In medicine it can be used as the intermediate of chlormezanone and dapsone aminobutyric acid and dye intermediates.
It can be used for the manufacturing of sedative chlormezanone and dye Acid Brilliant Blue 6B, etc.
In pesticide field, it can be used for the manufacturing of chlorine cinnamic aldehyde and weeding agent.
It can be applied to organic synthesis for making triphenylmethane and dye related intermediate.
Flammability and hazard properties
thermal decomposition can release toxic nitrogen oxides and chlorides fume.
water, carbon dioxide, foam, powder
Crystallise it from EtOH/water (3:1), then sublime it twice at ~50o/2mm. [Beilstein 7 H 235, 7 IV 568.]
oral-rat LD50: 1575 mg/kg; Oral-Mouse LD50: 1400 mg/kg
4-Chlorobenzaldehyde is combustible.
p-Chlorobenzaldehyde is a white solid with m.p. of 46~47 ℃, b.p. of 213~214 ℃ and n20D 1.5640, It is soluble in benzene, toluene and other solvents but insoluble in water.
warehouse: low-temperature, dry, ventilation