RU2568439C1 - Method of producing terephthalic aldehyde - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: terephthalic aldehyde is obtained from α,α,α',α'-tetrabromo-p-xylene while heating, followed by extraction of the end product. The method includes reacting α,α,α',α'-tetrabromo-p-xylene with O,O-dimethyl methylphosphonate at 180°C, and the end product is extracted from the reaction mass with isooctane.

EFFECT: method enables to obtain an end product with high output using a simple technique.

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Description

The invention relates to a method for producing terephthalaldehyde based on α, α, α ′, α′-tetrabrom-p-xylene and can be used for the production of fluorescent brighteners, dyes, pharmaceuticals, polymers for special purposes, materials for electronic devices and in other fields industry.

A known method of producing terephthalic aldehyde based on α, α, α ′, α′-tetrabrom-p-xylene by heating by hydrolysis with water in the presence of an alkali or alkaline earth metal salt, a phase transfer catalyst of tetrabutylammonium bromide or benzyltriethylammonium chloride and an alcohol-based solvent or ether, for example ethylene glycol or diglyme, which are soluble in water and have a boiling point of 120 to 250 ° C, the process is carried out at a temperature of 96 ° C. The yield of the target product is 80 wt.% Of theoretical, see JP Patent No. 09124538, IPC 6 С07С 47/544, B01J 31/02, С07С 45/43, С07В 61/00, 1997.

The disadvantage of this method is the insufficiently high yield of the target product and the complexity of the process.

The closest in technical essence is the method of producing terephthalic anhydride based on α, α, α ′, α′-tetrabromop-xylene by hydrolyzing it with water while heating and stirring, the process is carried out in the presence of an excess of sulfuric acid, at a temperature of 70 ° C raising the temperature to 110 ° C with removal of hydrogen bromide in vacuum, followed by isolation of the target product by pouring the reaction mass onto ice, washing the solid with water and recrystallizing it from 10% methyl alcohol with the addition of coal. The yield of terephthalaldehyde is 81-84 wt.%, See the collection "Syntheses of organic preparations", collection of articles. III, 1952, p. 397.

The disadvantage of this method is the insufficiently high yield of the target product and the complexity of the process.

The objective of the invention is to increase the yield of the target product and simplify the process.

The technical problem is solved by the method of producing terephthalaldehyde based on α, α, α ′, α′-tetrabrom-p-xylene by heating and subsequent isolation of the target product, in which α, α, α ′, α′-tetrabrom-p- xylene with O, O-dimethylmethylphosphonate at a temperature of 180 ° C, and the selection of the target product is carried out by extraction from the reaction mass with isooctane.

The solution to the technical problem allows to increase the yield of the target product by 16% and to simplify the process due to the absence of sulfuric acid, the absence of the formation of hydrogen bromide and the use of isooctane instead of methyl alcohol in the process of obtaining the target product.

The characteristics of the substances used in the method:

Terephthalaldehyde (Benzenedicarbaldehyde-1,4) of the formula

Colorless crystals with so pl. 115-116 ° C, bp 247 ° C. Soluble in ethanol, ether.

α, α, α ′, α′-tetrabrom-p-xylene [1,4-bis- (dibromomethyl) benzene] of the formula

White crystals with so pl. 168 ° C, insoluble in water, soluble in hot chloroform and carbon tetrachloride. O, O-dimethylmethylphosphonate of the formula

MeP (O) (OMe) ₂

Colorless liquid 58-59 ° C at 8 mm Hg The invention illustrates the following examples of specific performance.

Example 1

4.22 g (0.01 mol) of α, α, α ′, α′-tetrabromop-xylene and 3.1 g (0.025 mol) of O, O-dimethylmethylphosphonate are taken; the reaction is carried out at 180 ° С until the ¹ H resonance signal disappears in the NMR spectrum at δ 6.63 ppm, related to the proton of the dibromomethyl group. Terephthalaldehyde in the form of crystals is isolated by extraction with isooctane. Colorless crystals of the target product have a melting point of 115-116 ° C. The yield of terephthalaldehyde is 1.29 g (96% by weight).

Example 2

7.60 g (0.018 mol) of α, α, α ′, α′-tetrabromop-xylene and 5.58 g (0.045 mol) of O, O-dimethylmethylphosphonate are taken, the reaction is carried out at 180 ° С until the resonance signal disappears in the ¹ H NMR spectrum at δ 6.63 ppm, related to the proton of the dibromomethyl group. Terephthalaldehyde in the form of crystals is isolated by extraction with isooctane. Colorless crystals of the target product have a melting point of 115-116 ° C. The yield of terephthalaldehyde is 2.33 g (96 wt.%).

Thus, the claimed method for producing terephthalic aldehyde in comparison with the prototype allows to increase the yield of the target product by 16% and to simplify the process due to the absence of sulfuric acid, the absence of the formation of hydrogen bromide and the use of isooctane instead of methyl alcohol in the process of obtaining the target product.

Claims (1)

A method of producing terephthalic aldehyde based on α, α, α ′, α′-tetrabrom-p-xylene by heating, followed by isolation of the target product, characterized in that α, α, α ′, α′-tetrabrom-p-xylene interact with O, O-dimethylmethylphosphonate at a temperature of 180 ° C, and the selection of the target product is carried out by extraction from the reaction mass with isooctane.