SU680641A3 - Method of obtaining 3-brombenzaldehyde - Google Patents

Description

I

The invention relates to methods for producing substituted benzaldehydes, specifically to a method for producing 3-bromobenzaldehyde, which is an intermediate product for obtaining 3-phenoxybenzyl alcohol derivatives, which form insecticidal esters with certain carboxylic acids.

A known method for producing 3-bromobenzaldehyde by reserving benzaldehyde with molecular bromine in the presence of aluminum chloride at a molar ratio of reagents - bromine and benzaldehyde is 1.1: 1 in 1,2-dichloroethane at a temperature of 3545 ° C. The yield of the target product is 70% 1.

The disadvantages of the known method for producing 3-bromobenzaldehyde are the high consumption of bromine and the insufficiently high yield of the target product.

The aim of the invention is to increase the yield of the target product and reduce its cost.

This goal is achieved by the method of producing 3-bromobenzaldehyde by brominating benzaldehyde in a chlorinated alkane medium and in

the presence of aluminum chloride with a mixture of chlorine and bromine at a molar ratio of 0.90-1.0: 1.0, respectively, at a temperature of 3-25 ° С. Chlorine and bromine can either be mixed - up to contact with benzaldehyde, for example, by removing their solution in chlorinated hydrocarbon (the preferred option), or you can introduce chlorine and bromine separately into a mixture of benzaldehyde, A.shominy chloride and a solvent.

Distinctive features of the method are: the implementation of bromination with a mixture of chlorine and bromine at a molar ratio of 0.9-1.0: 1.0, respectively, and carrying out the process at a temperature of 3-2. PRI me R -1. 0.5 mole chlorine

Add a solution of 0.5 mol of bromine in 20 ml of 1,2-dichloroethane, cooled by solid CO2 in isopropanol, and the resulting solution is diluted with 100 ml of 1,2-dichloroethane. The resulting solution is added over a period of 2 hours and 20 minutes to a mixture of 1.3 mol of chloride of ash and 1.0 mol of benzaldehyde in 200 ml of 1,2-dichloroethane at 23–25 ° C. The mixture is then stirred for another 1 hour at this temperature.

At this stage, the conversion of benzaldehyde is 89% and the selectivity for 3-bromobenzaldehyde is 9596% (according to GLC).

The reaction mixture is diluted with enough water to dissolve the aluminum hydroxide precipitate. The organic layer is separated, washed with 100 ml of water and dried (magnesium sulfate). The solvent is distilled off, the residue is subjected to fractional distillation and 3-bromobenzaldehyde is obtained, b.p. at 1.5 mm Hg, 79% yield ,.

Example 2. 1.3 mol of benzaldehyde was added over 0.75 h, JC of a mixture of 1.43 mol of aluminum chloride and 500 ml of 1,2-dichloroethane at. 0.65 mol of liquid bromine is added to the mixture at 15 s, chlorine gas is passed into the mixture at

Conditions for the reaction of the brog "1benzaldeg" and the yield of 3-bromobenzaldehyde

, 15 ° C for 2 hours until a molar ratio of chlorine to bromine reaches 0.95: 1. The mixture is stirred for another 1 h at. A solution of 0.0355 mol of formic acid in 500 ml of water is added to the reaction mixture to destroy the excess bromine. The organic layer is separated, washed with 500 ml of water containing sodium silent sulfate (to promote separation) and then 500 ml of water. Wash water is collected and extracted with 250 MP of 1,2-dichloroethane. Collect the two organic phases and analyze by GLC. The results are shown in the table.

Examples 3-19. The reaction is carried out under the conditions of Example 2. The reaction conditions and results are shown in the table.