JPS5912104B2 - Production method of P-nitrobenzaldehyde - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention produces p-nitrotoluene by reacting p-nitrotoluene with bromine.
The present invention relates to a method for producing p-nitrobenzaldehyde, which is characterized in that nitrobenzal bromide is obtained and then hydrolyzed in a sulfuric acid solution, whereby highly pure p-nitrobenzaldehyde can be produced economically.

p-Nitrobenzaldehyde is a very important intermediate in the synthesis of pharmaceuticals and dyes, and being able to obtain and use it in pure form is of great importance.

As an example of an excellent method for producing this intermediate, p-nitrobenzyl alcohol is oxidized with nitric acid to obtain p-nitrobenzaltehyde in a yield of 80-90% in East German Patent Specification 9.
There is a method of No. 912, but p-nitrobenzyl alcohol used here is expensive, and German patent specification No. 956497, in which p-nitrobenzyl chloride is oxidized with nitric acid to obtain p-nitrobenzaldehyde with a yield of 73%.
There is method No. 5, but this method requires three steps to isolate p-nitrobenzyl chloride, oxidize it with nitric acid, extract it, and purify it, and also requires a large amount of nitric acid.

Therefore, p-nitrobenzaldehyde is a very expensive intermediate in conventional production methods. On the other hand, as a synthesis method for p-nitrobenzaldehyde, p-nitrobenzaldehyde is derived from p-nitrobenzal halide by condensing p-nitrobenzal halide with morpholine and hydrolyzing this condensate with hydrochloric acid, yielding 82-91%. % p-nitrobenz 15
Report on obtaining aldehydes, Compt-Rend. 2
52493-5 (1962) is known.

However, when p-nitrotoluene is used as a raw material, a three-step process is required, as p-nitrobenzal halide must be synthesized and isolated, condensed and isolated with morpholine, and then the condensate must be hydrolyzed with hydrochloric acid. The isolation process of p-nitrobenzal halide is very expensive and furthermore requires the use of large amounts of morpholin. Therefore, from an economic standpoint, this method has not yet been put into practical use. Next, in 25, a method of hydrolyzing a dihalomethyl group to obtain an aldehyde includes toluene and -Cl, -Br, -F
, -CN, hydrolyzing benzal halide obtained by dichlorination or dibromination of a toluene derivative having an acetoxy group with calcium carbonate or 30 sulfuric acid to obtain the corresponding aldehyde in a yield of 50-70%, 2-
Acetoxy-4-nitrobenzal bromide was hydrolyzed to give 2-oxy-4- in good purity after three recrystallizations.
J, A, and C who synthesized nitrobenzaldehyde
,S. 35 and 825 (1942) is known, but the yield of this method is unknown, and the results of our follow-up tests show that 2-acetoxy 4-nitropene IA゜-
Zalpromide yield was 20-30%.

Compared to these methods, the method of the present invention surprisingly found that p-nitrobenzaldehyde can be obtained in high purity and in high yield when p-nitrobenzalbromide is heated in sulfuric acid. Ta. In addition, although it is difficult to synthesize p-nitrobenzal chloride in good yield by dibromination of o-nitrotoluene and chlorination of p-nitrotoluene, it is possible to synthesize p-nitrobenzal chloride by dibromination of p-nitrotoluene. By adding sulfuric acid to the crude brominated product and heating it, p-nitrobenzaldehyde containing a small amount of p-nitrobenzoic acid can be obtained in good yield. It has been found that p-nitrobenzaldehyde can be obtained. According to this method, bromination and hydrolysis can be done in one step using p-nitrotoluene as a starting material. Therefore, even if we add the step of separating p-nitrobenzaldehyde and p-nitrobenzoic acid, it is still a two-step process starting from p-nitrotoluene.
High purity p-nitrobenzaldehyde can be obtained in a good yield, and it is an innovative method as an industrial production method from the viewpoint of efficiency and economy. To describe the method of the present invention in detail, 10 parts of p-nitrotoluene is mixed with 23 parts to 31 parts of p-nitrotoluene.
The brominated product is synthesized by reaction with preferably 2529 parts of bromine at 100-200°C, preferably 140-160°C, and further reacted with 25-150 parts of bromine, preferably 40°C.
-100 parts, with a concentration of 80-98%, preferably 90-100 parts.
Add 95% sulfuric acid at 50-150°C, preferably 90-150°C.
It is recommended to react at 100°C.

Bromine is also recovered as hydrogen bromide and bromine in the bromination and hydrolysis steps. High purity p-nitrobenzaldehyde can be easily obtained by recrystallizing p-nitrobenzaldehyde and p-nitrobenzaldehyde from an organic solvent such as carbon tetrachloride, water, or a small amount of sodium bicarbonate. This synthesis method can easily achieve a purity of 99% or more, M. p-Nitrobenzaldehyde of p44!06°C can be produced with a yield of 81% based on p-nitrotoluene.

In addition, P as a by-product with a yield of 5-20% relative to p-nitrotoluene
'Nitrobenzoitsuquaside can be obtained.

The process for preparing p-nitrobenzaldehyde according to the invention is explained in more detail by the following examples.

Parts and percentages used herein are by weight. Quality data is based on quantitative gas chromatography. Example 110
Heating 2 parts of p-nitrotoluene to 140-150°C
6 parts of bromine are added dropwise into the solution over a period of about 9 hours, followed by keeping at the same temperature for a further 3 hours (21 parts of crude brominated product are produced).

Also, hydrogen bromide gas generated during bromination is recovered during the reaction)
. Further, the reactor was cooled to 7580°C, 90 parts of 93% sulfuric acid was added at 75-80°C, and then heated to 95°C for 5 hours while the generated hydrogen bromide and bromine gas were collected from the upper part of the reactor into an absorption trap. Make it react. The mixture was then added dropwise to 180 parts of ice water, and the product was filtered and washed with water until the pH reached 4, yielding about 23 parts of wet product. This wet product (11.2 parts dry) is boiled for 1 hour in 70 parts carbon tetrachloride, 17 parts water, and 2.2 parts sodium bicarbonate. It is then cooled to 15 DEG C. and the product is filtered, yielding 90 parts of 99% pure p-nitrobenzaldehyde. (corresponding to a theoretical yield of p-nitrotoluene of 80.9% of pure material) M. p. The aqueous layer was separated at 1O6°C and precipitated with sulfuric acid or hydrochloric acid to obtain 0.61 part of p-nitrobenzoic acid. M. p. 23
O-235°C (corresponding to a theoretical yield of 5%). Also, carbon tetrachloride is distilled and used repeatedly. Example 2 10 parts of p-nitrotoluene was heated to 140-150°C, 27 parts of bromine was added dropwise into the liquid over about 9 hours, and the temperature was kept at the same temperature for an additional 3 hours (21.6 parts of brominated crude Product is formed) further cooled to 75-80°C and 93% of 42 parts
After addition of sulfuric acid at 75-80°C, as in Example 1, approximately 23 parts of wet product are obtained (11.2 parts when dry) which is treated as in Example 1 to give 8 .4 parts of 99% pure p-nitrobenzaldehyde are obtained.

Claims (1)

[Claims] 1. A method for producing p-nitrobenzaldehyde, which comprises reacting p-nitrotoluene with bromine to obtain p-nitrobenzal bromide, and then hydrolyzing it in a sulfuric acid solution.