SU39111A1 - A method for reducing aromatic nitro compounds - Google Patents

Description

The present invention relates to methods for reducing aromatic nitro compounds with iron or electrolytic in the presence of iron salts and acids.

When paranitroanisole and phenetol are reduced, the reaction does not proceed smoothly and the consumption of iron usually exceeds ZOO / o from the theoretical value. In addition, due to the poor solubility of the above nitro compounds in water, most of the liberating hydrogen does not react. The introduction of an excess of iron necessitates the use of large amounts of acid, resulting in large volumes of solutions, from which it is difficult to saline with a good yield of amine hydrochloride.

The authors of the present invention proposed the reduction of aromatic nitro compounds with iron or by electrolysis in the presence of iodine salts as a catalyst. With the addition of insignificant amounts of iodine salts, the reduction reaction proceeds more intensively as in the case of reduction with iron, as well as by electrolysis.

The exuding hydrogen is almost completely absorbed, and iron is required to be introduced only in a slight excess versus theoretical.

Example 1. 1 mole of paranitroanisole is added to 1.5 liters of the 7th normal

hydrochloric acid, 5 g of potassium iodide are added and the reduction process is carried out with the gradual addition of 200 g of iron shavings and with vigorous stirring at 80 - 90 °. The reaction takes about 5 hours, and the nitroanisole is completely dissolved. The liquid is filtered and the resulting anisiline hydrochloride is salted out by adding 200 g of sodium chloride.

The output of anisiline hydrochloride 115 g- 72 ° / o theoretical.

Example 2. 170 g of paranitrophenetol are introduced into 2.5 liters of four-normal hydrochloric acid, b g of potassium iodide is added and reduced, as indicated in Example 1, by the addition of 220-240 g of iron shavings.

The filtered solution is salted out with 150 g of sodium chloride, and phenetidine hydrochloride remains in the mother liquors after separation of the crystals.

In order to purify, phenetidine hydrochloride is dissolved by heating in 4 parts of 5 / o-hydrochloric acid, boiled with coal and a small amount of hydrosulfite, filtered, and then phenetidine hydrochloride is precipitated by adding an equal volume of strong hydrochloric acid.

After cooling, phenethidine hydrochloride is sucked off. The yield of pure product is 138 g or SOVo theoretical. Water and hydrochloric acid up to 2.4 liters four-normal are added to the mother liquor after recrystallization, after which it is regenerated.

Example 3. 334 g of paranitrophenetol are loaded together with 930 cu. cm 40% sulfuric acid, TOO g of ferrous sulfate and 7 g of potassium iodide in the cathode space of the electrolyzer with a porous diaphragm.

The cathode is copper, and the anode is lead in S / o sulfuric acid. The mixture is heated to 60 - 80 ° and at a current density of 10 amps per 1 square meter. ds, 336 amps / hour is passed, after which the current density is reduced by half and about another 100 amperes / hour is passed until nitrophenetol is completely dissolved. The solution obtained after electrolysis is heated with coal, filtered and salted out with the addition of 200 g per 1 liter of sodium chloride.

The hydrochloride precipitated during cooling is sucked off, washed with sodium chloride solution and dried. Output-75 / a theoretical.

The solution obtained after electrolysis can also be processed by heating, after which it is filtered and the precipitated phenetidine sulfate is sucked off after cooling. Output - 150 g of EZ / about-th product or 0.752 mol.

The subject matter of the invention.

A method of reducing aromatic nitro compounds with iron or electrolytically in the presence of iron salts to acids, characterized in that iodide salts are used as catalysts for the reaction.