CS242285B1 - Method of 3-nitrobenzaldehyde production - Google Patents

Abstract

The present invention relates to a process for the preparation of 3-nitrobenzaldehyde, which consists in being nitration is carried out in a concentrated environment of sulfuric acid with a nitrating mixture in the presence compounds of the formula RCONHz where R represents hydrogen or amino molar the ratio of the hydrohenzamide components of the formula II: nitric acid: general compound Formula RCONH2 1: 4 to 8: 0.01 to 0.03 at at a temperature of 10 to 35 ° C, and then, after decomposition reaction mixture with ice and water to give the product of formula I.

Description

The compound is an important intermediate in the organic industry with wide application in the field of organic dyes, crop protection agents and pharmaceuticals, eg X-ray diagnostics, jopanoic acid (Dye Review, SNTL Prague 1968; Chemie der Pflanzenschutz- und Schadingsbekampfungsmittel, Vol. 1 to 8) Verlag, Berlin, The Chemistry of Nitro and Nitroso Groups (Ed. H. Feuer) Interscence, New York 1970, Russian translation by Izd. Mir, Moscow 1973; J. Amer. Chem. Soc. 71, 3753, (1949), Amer. Chem., Soc., 80, 4949 (1958), Row O .: Jopagniost, VÚFB Final Report (1959)].

To date, the 3-nitrobenzaldehyde of formula I has been industrially produced in essentially two ways. In the first, direct nitration of benzaldehyde is carried out using a considerable excess of the nitration mixture, often requiring anhydrous nitric acid (see, for example, the VÚFB final report and references cited therein, Methoden der Organischen Chemie (Houben Weylj Volume 10/1, G. Thieme Verlag, Stuttgart 1971) This process has a number of disadvantages, using a multiple excess of the nitration mixture, and the use of anhydrous nitric acid poses considerable safety and hygiene risks, generating 5-15% of the undesired o-isomer, which is difficult to remove by crystallization from a fire point of view. The second method uses the readily available 1,3,5-triphenyl-2,4-diaza-1,4-pentadiene (hydrobenzamide) of formula II (C6H5CN = N) 2CH-CeH5 (II), which, when dissolved in an excess of sulfuric acid monohydrate, nitrates with a mixture prepared from monohydrate k sulfuric acid and concentrated nitric acid at a temperature of 0 to 18 ° C, using only 2.4 moles of nitric acid per mole of hydrobenzamide of formula II (theoretical consumption per mole of compound of formula II is 3 moles of nitric acid). An isomerically pure product of formula I containing up to 1% of the o-isomer is obtained. The disadvantage of this process is the contamination of the desired product of formula I with the remainder of the hydrobenzamide and its decomposition products, a relatively long reaction time and the necessity of recrystallization of the product before further use.

These processes are followed in a positive way by the process according to the invention, which partially or completely removes the above disadvantages.

The process of the invention is based on nitration of hydrobenzamide of formula II in concentrated sulfuric acid in the presence of 0.01 to 0.03 mol of urea or formamide relative to 1 mol of hydrobenzamide of formula II with a nitration mixture of concentrated nitric acid and sulfuric acid in a 1: 0 volume ratio. 6 to 0.8 in an amount of 4 to 8 moles per mole of hydrobenzamide. According to the invention, the dry hydrobenzamide of the formula II is dissolved with stirring in concentrated sulfuric acid at a temperature of 10 to 15 ° C and then a nitration mixture containing 4 to 8 moles of nitric acid per mole of the compound of formula II is added over 3-4 hours. then slowly warm to 30-35 ° C after the addition is complete. The progress of the reaction can be monitored by silica gel thin layer chromatography for 4 to 6 hours. After cooling again, the reaction mixture is poured onto an equal volume of ice and water. The precipitated oily product crystallizes slowly - after about 15 to 30 minutes, after suctioning it is washed thoroughly with water until neutral reaction to the methylchlorate. The dried product of formula I contains less than 0.5 percent of the o-isomer according to gas chromatography analysis.

An advantage of the process of the invention is the high isomeric purity of the product of formula (I), which is obtained in high yields. In most cases, it is used for further synthesis steps without purification. Another advantage is that it replaces 95 to 99% nitric acid with commercially available concentrated nitric acid.

The process according to the invention is illustrated by several examples which are illustrative only and do not limit the scope of the invention in any way.

Example 1

310 g (1.04 mol) of hydrobenzamide (Formula II) and 1 g of urea were successively added to 1460 g (800 ml) of concentrated sulfuric acid at 10-15 ° C. After dissolution of the hydrobenzamide, a nitration mixture (1,238 g) prepared from 477 ml of concentrated nitric acid and 315 ml of concentrated sulfuric acid was added slowly, so that the temperature of the reaction mixture did not exceed 15 ° C (external ice and salt cooling). Then everything was slowly heated to 30-35 ° C. The progress of the reaction was checked by thin layer chromatography on silica gel and after stirring for 4 hours the mixture was poured onto an equal volume of ice. The oily product precipitated slowly crystallized, was sucked off on a frit and washed several times with ice water until neutral. After drying the suction crystals in a vacuum desiccator, 422 g (90%) of the product of formula I, m.p. 55-57 ° C, were obtained, which according to gas chromatography analysis contained 0.45% of the undesired o-isomer. The literature reports a melting point of 58 ° C.

Example 2

To a solution of hydrobenzamide in concentrated sulfuric acid (62 g of hydrobenzamide in 160 ml of sulfuric acid) was added 0.3 ml of formamide and then 220 g of nitration mixtures as in Example 1 were slowly added dropwise at a reaction temperature of 10-15 ° C. 87 g of the product of formula I, mp 55-57 ° C, which, according to gas chromatography analysis, contained 0.5% of the o-isomer, was obtained.

Claims (1)

SUBJECT A process for the preparation of 3-nitrobenzaldehyde of formula I no ₂ (0 starting from formula II of hydrobenzamide (C 6 H 8 CH 3 N 2 CH 3 C 6 H ₂ ), which in nitrous sulfuric acid medium is nitrating mixture composed of concentrated nitric acid and the nitration is carried out in a medium with a nitration mixture in the presence of a compound of the formula III, RCONH2 (III), wherein R is hydrogen or amino, in a molar ratio of the components hydrobenzamide of formula II: nitric acid: compound of formula III 1: 4 to 8: 0.01 to 0.03 at 10 to 35 ° C, then after decomposing the reaction mixture with ice and water, the product of formula (I) is obtained.