SU793986A1 - Method of preparing p-methoxybenzaldehyde - Google Patents

Description

one

This invention relates to an improved process for the preparation of P-methoxybenzaldehyde, widely used in the pharmaceutical, perfume and food industries.

A known method for producing p-methoxybenzaldehyde by oxidizing p-cresol methyl ester with persulfuric acid in the presence of He ions or Cu ions l3.

The disadvantage of this method is the instability of the oxidation process, due to the lack of control over the oxidation of p-cresol methyl ester.

The closest technical solution to this problem is a method for producing p-methoxybenzaldehyde by oxidizing P-cresol methyl ester in a sulphate solution with pyrolusite. The process is carried out by gradual addition of pyrolusite at room temperature, followed by holding the reaction mass for 6 hours at 70-80 C. Methyl ether P-cresol and pyrolusite are taken in a molar ratio of 1: 2.

Isolation of the final product is carried out by benzene extraction followed by distillation of benzene.

extract in vacuum. The yield of p-methoxmbenzaldehyde is 46-55%,

main product content

99.4% 121.

The disadvantages of the known method for producing p-methoxybenzaldehyde are the low yield and quality of the final product, the instability

of the oxidation process, due to the lack of control over the oxidation of the methyl ester of i-Cresol, as well as the use of an organic solvent at the stage of isolation

target product.

The purpose of the invention is to increase, yield and quality of the target product, simplifying the process. The goal is achieved

described method of obtaining

r -methoxybenzaldehyde, which consists in the process of oxidizing t-cresol methyl ester with manganese dioxide in a medium

sulfuric acid at a molar ratio of the above reagents 1: 1.651, 7 at 69-72 s. A distinctive feature of the proposed method is that the process is carried out

with redox

a potential of 0.55-0.60 V and isolation of the target product is carried out by splitting and separating the organic layer from the aqueous layer, crystallizing the organic layer upon cooling to, followed by filtering the resulting target product and purifying by vacuum distillation. The yield of the target product is 73-75%, the content of the main substance is 99.94-99.96%.

N and p To a mixture of 652 ml (1.612 mol) of 21% sulfuric acid and 40.0 g (mol) of methyl ester of t1 -cresol at a temperature of 69-72 0 and a redox potential of 0.47 V is added in portions, manganese dioxide in 4 , 6 g 10 servings and the last serving 2.0 g, total 48 g (0.552 mol) of MnOj. During oxidizer loading, the potential increases sharply to 1.0–1.1 V and falls within 30 minutes as the latter is consumed. Each portion of manganese dioxide is loaded with a decrease in the redox potential of the system to 0.55-0.60 V. The reaction mass after the last addition of oxidant is maintained at 69-72 ° C until the potential is not higher than 0.55-0.60 B. A settling mixture separated the organic layer from the aqueous layer, cooled the organic layer before and filtered from the salts. The resulting technical product is purified by vacuum distillation. The analytical yield of p-methoxybenzaldehyde, determined using gas-liquid chromatography is 87%. After fractionation in vacuum, 33.7 g of p-methoxybenzaldehyde are obtained (yield 74.6% on loaded methyl ester of M-cresol) with the content of the main substance 99.95% by gas-liquid chromatography, density 1.124, refractive index 1.57.30.

The proposed method allows:

stabilize the oxidation of p-cresol methyl ester by eliminating temperature jumps in the process of adding an oxidant,

to increase the yield of the target product to 73-75% against 46-55%;

in quality (99.94-99.96%) approximate in natural h-methoxybenzaldehyde (anisic aldehyde), extracted from essential oils,

reduce oxidant consumption by

sixteen%;

improve sanitary and hygienic working conditions by eliminating the use of a toxic organic solvent.

Claims (2)

1. The patent of Germany 222116, cl. C 07 C 47/56, published 1976. 2..M.S. Tovbina, N.A. Daev and V.M. Dashunin. Preparation of p-methoxybenzaldehyde by oxidation of p-cresol methyl ester, -PPH, 1971, 3, p. 681-682 (prototype).