English name: 3-Bromobenzaldehyde
Molecular formula: C7H5BrO
Molecular weight or atomic weight: 185.03
Density: 1.587
Boiling Point (℃): 233 ~ 236
Flash point (℃): 96
CAS No.: 3132 -99-8
3-Bromobenzaldehyde is a white to pale yellow crystal. It is insoluble in water, soluble in ethanol and ether. 3-Bromobenzaldehyde mainly used for spices, dyes and organic synthesis intermediates.
Preparation of 3-Bromobenzaldehyde is a bromine toluene as raw material, in the light bromide to generate bromobenzyl bromide compound is hydrolyzed under alkaline conditions, the last steam distillation, cooling and crystallization, washed with cold water and recrystallized from ether derived. Here are 3 examples for the preparation of 3-Bromobenzaldehyde:
EXAMPLE 1
A 500 ml water-cooled glass vessel was fitted with a reflux condenser cooled with a mixture of acetone and solid carbon dioxide, an inlet and an outlet for nitrogen, a propeller stirrer, baffles and a dropping funnel. 200 ml of 1,2 -dichloroethane and 1.3 moles of aluminum chloride were placed in the vessel. Then, 1 mole of benzaldehyde was added slowly from the dropping funnel with stirring. The benzaldehyde formed a complex with aluminum chloride, which complex partly dissolved in the 1,2 -dichloroethane.
In another vessel 0.5 mole of bromine was added to 20 ml of 1,2 -dichloroethane, the vessel being cooled in a mixture of acetone and solid carbon dioxide. 0.5 mole of chlorine was added to the mixture thus formed and subsequently so much 1,2 -dichloroethane was added until the total volume was 100 ml.
The solution of bromine chlorine thus obtained was added over a period of 2 hours and 20 minutes through the dropping funnel to the mixture containing the complex of benzaldehyde and aluminum chloride and the reaction mixture was stirred for a further hour. During the reaction hydrogen chloride escaped from the reflux condenser. The temperature of the reaction mixture was kept between 23 discontinued and the reaction mixture was analyzed by means of gas-liquid chromatography. The conversion of the benzaldehyde was 89 % and the selectivity to 3-bromobenzaldehyde was higher than 99 %.
So much water was mixed with the reaction mixture that the precipitated aluminum hydroxide dissolved. The mixture thus obtained settled into an aqueous layer and an organic layer. The organic layer was separated, washed with 100 ml of water and dried over anhydrous magnesium sulphate. The dried organic layer was boiled down and the residue obtained was separated by distillation into benzaldehyde and a residue of 3 -bromobenzaldehyde, boiling at a temperature of 80 pressure of 1.5 Torr.
EXAMPLE 2
The experiment described in Example 1 was repeated with 1.1 moles of aluminum chloride instead of 1.3 moles. Bromination of benzaldehyde to 3 -bromobenzaldehyde did occur, but less than 2 % of it was converted after 1 hour and less than 5 % after 4 hours’ reaction time.
EXAMPLE 3
The experiment described in Example 1 was repeated with 1.2 moles of aluminum chloride instead of 1.3 moles. After 4 hours’ reaction time about 70 % of the benzaldehyde was converted into 3-bromobenzaldehyde.
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