CS243193B1 - Process for preparing 4-aminotoluene-2-sulfo-N-ethyl-anilide - Google Patents

Abstract

Method for producing 4-aminotoluene-2-sulfo-N-ethylanilide by reduction of the corresponding nitro compound in a melt with an aqueous solution of hydrazine hydrate. The essence of the solution lies in the fact that the reduction is carried out under homogeneous catalysis of ferrous salts of strong inorganic acids, such as ferrous chloride, ferrous sulfate or ferrous nitrate. The amount of ferrous salts of strong inorganic acids used corresponds to 0.4 to 1.2% by weight, based on the starting nitro compound. After the reduction, the reaction mixture is introduced into 0.05 to 1.5% hydrochloric acid containing 0.3 to 2% of an alkyl polyglycol ether surfactant (Slovasol 0).

Description

The present invention relates to a process for the preparation of 4-aminotoluene-2-sulfo-N-ethylanilide which serves as a semi-finished product for the production of Midlon dyes.

The method used to date to produce 4-aminotoluene-2-sulfo-N-ethylanilide consists in reducing 4-nitrotoluene-2-sulfo-N-ethylanilide with 80% hydrazine hydrate in the presence of a heterogeneous catalyst - iron powder, dissolving the reducing mixture in 4% hydrochloric acid, with activated carbon, precipitation of 4-aminotoluene-2-sulfo-N-ethylanilide with aqueous ammonia solution and in product cleration. (% By weight means weight.)

The reaction proceeds according to the following equation:

The described process has some drawbacks because it is lengthy and the operator has to pay close attention to the precautions during the hydrazine reduction because it is too stormy and accompanied by foaming. It also imposes increased requirements on corrosion resistant materials in dilute and warm hydrochloric acid environments when the amine melt is dissolved prior to cleration.

The above disadvantages are overcome by a process for the preparation of 4-amino-toluene-2-sulfo-N-ethylanilide by reducing 4-nitrotoluene-2-sulfo-N-ethylanilide with an aqueous solution of the hydrazine derivative in the melt of the starting nitro compound of the invention. the reduction is carried out under homogeneous catalysis of ferrous salts of strong inorganic acids, for example ferrous chloride, ferrous sulphate and / or ferrous nitrate in an amount of 0.4 to 1.2% by weight, preferably 0.6 to 0.8% by weight, based on the starting material nitro compound, then the reaction mixture is introduced into 0.05 to 1.5% by weight hydrochloric acid containing 0.3 to 2% by weight, preferably 0.7 to 1.5%, alkyl polyglycol ether type surfactant.

Advantages of the process according to the invention are labor saving, less labor and increased safety of work during hydrazine reduction, which is considered to be at risk.

In order to further elucidate the invention, examples are given in which percentages are by weight.

Obviously, the scope of the invention is not exhaustive or limited.

Examples

Example 1 g of 4-nitrotoluene-2-sulfo-N-ethylanilide (calculated to 100%) as a wet product is melted, water is distilled off and the melt temperature is raised to 110 ° C. After the addition of 0.8 g of crystalline ferrous sulphate, 26.2 g of 80% by weight hydrazine hydrate were added dropwise at 105-110 ° C over 2 hours, followed by stirring at the same temperature for 2-3 hours at the end of the reduction. . The melt is cautiously heated at 20 to 60 ° C to 400 ml of 0.15% hydrochloric acid containing 3 g of a dissolved alkyl polyglycol ether type surfactant (Slovasol 0), which causes fine granulation of the product. 54 g of 4-aminotoluene-2-sulfo-N-ethylanilide (100%) are obtained in a yield of 93% of theory.

Example 2

320 g of 4-nitrotoluene-2-sulfo-N-ethylanilide, calculated as 100% of the substance in the form of a wet product, are introduced into a stainless steel reducer, the product is melted and, after distilling off water, 3 g of crystalline ferric chloride are added. Next, 131 g of 80% hydrazine hydrate was added dropwise to the melt over a period of 2 to 3 hours at 105 to 115 ° C, followed by stirring at the same temperature for 3 hours to complete the reduction. The melt is then poured at 40 ° C into 2000 ml of 0.35% hydrochloric acid containing 14 g of an dissolved alkyl polyglycol ether type surfactant (Slovasol 0).

The further procedure is identical to the first exemplary embodiment.

Yield: 275 g of 4-aminotoluene-2-sulfo-N-ethylanilide (as 100%) and represent 95% of theory.

Example 3

The procedure is the same as in Example 1, except that 0.7 g of ferrous nitrate is used in place of ferrous sulfate and the concentration of hydrochloric acid is 1% by weight. The yield was 52 g of 4-aminotoluene-2-sulfo-N-ethylanilide (as 100%) and represented 89.6% of theory.

Claims (1)

SUBJECT OF THE INVENTION Process for preparing 4-aminotoluene-2-sulfo-N-ethylanilide by reducing 4-nitrotoluene-2-sulfo-N-ethylanilide with an aqueous solution of hydrazine hydrate in a melt of a nitro compound, characterized in that the reduction is carried out under homogeneous catalysis of ferrous salts of strong inorganic acids of ferrous, ferrous sulphate and / or ferrous nitrate in an amount of 0.4 to 1.2% by weight, preferably 0.6 to 0.8% by weight, based on the starting nitro compound, after which the reaction mixture is introduced into 0.05% hydrochloric acid % to 1.5% by weight with a content of 0.3 to 2% by weight, preferably 0.7 to 1.5% by weight, of an alkyl polyglycol ether type surfactant.