CS237717B1 - Method of isolation of 3-methyl-4-nitrophenol - Google Patents

Abstract

Method for isolating 3-methyl-4-nitrophenol from an aqueous solution of sodium 3-methyl-4-nitrophenolate containing, as impurities, inorganic salts, organic compounds of phosphorus, sulfur and/or chlorine, and residues of an aromatic solvent. 3-methyl-4-nitrophenol is obtained from a solution of sodium 3-methyl-4-nitrophenolate from the production of O,O-dimethyl-O-(3-methyl-4-nitrophenyl)thiophosphate by precipitation with mineral acid to a pH value of 1 to 6. The precipitated 3-methyl-4-nitrophenol is separated from the impurities, e.g. by filtration. A mineral acid containing 3-methyl-4-nitrophenol as an impurity is used to adjust the pH value. The adjustment of the pH value is preferably carried out in the presence of a defoamer. The method can be used in the production of 3-methyl-4-nitrophenol, which is used as an intermediate in the production of insecticides.

Description

237717 2

The invention relates to the isolation of 3-methyl-4-nitrophenol from an aqueous solution of sodium 3-methyl-4-nitro-phenolate. 3-Methyl-4-nitrophenol is used as an intermediate for the preparation of organophosphate insecticides, especially O, O-dimethyl-O- (3-methyl-4-nitrophenyl) tlophosphate.

Most often, 3-methyl-4-nitrophenol is prepared by two-stage nitrosation of 3-methylphenol and oxidation of 3-methyl-4-nitrosophenol with nitric acid. In addition to the desired 3-methyl-4-nitrophenol, the lower yield-reducing isomers are also formed on the HNO-coating. Known for the preparation of 3-methyl-4-nitrophenol by reaction of methyl toluidine with sodium nitrite in the presence of sulfuric acid. In addition, 3-methyl-4-nitro-phenol is prepared by necrosis of 3-methylphenol with acid-like acid and subsequent oxidation of 3-methyl-4-nitrosophenol to 3-methyl-4-nitrophenol in the sulfuric acid medium (Bridge Morgan, J. Am. Chem. Soc. 20 766) (1898) in concentrated sulfuric acid (US Pat. No. 1,502,849).

The oxidation of 3-methyl-4-nitrosophenol is carried out with nitric acid (Koelsch, J. Am. Chem. Soc. 66. 2019 (1944)), MS. pat. 146 179 and MS. AO 149 726). Oxidation of 3-methyl-4-nitrosophenol with hydrogen peroxide in an alkaline medium is described in Travagli, Chem.

Abstr. & 7594 e (1951).

Reference is made in the above references to the isolation of 3-methyl-4-nitrophenol by-products resulting from the production of O, O-dimethyl-O- (3-methyl-4-nitrophenyl) thiophosphate. '

The aforementioned drawbacks are eliminated according to the invention by the isolation of 3-methyl-4-nitrophenol, from an aqueous solution of sodium 3-methyl-4-nitrophenolate containing impurities such as inorganic salts, organic compounds of phosphorus, sulfur or chlorine, residues of aromatic solvents 0, O-dimethyl-O- (3-methyl-4-nitrophenyl) thiophosphate. 3-Methyl-4-nitrophenol is precipitated from the aqueous solution of 3-methyl-4-nitrophenolate by adjusting the pH to 1 to 6. The precipitated 3-methyl-4-nitrophenol is separated from the dissolved impurities by, for example, filtration or centrifugation.

The pH of the aqueous solution of 3-methyl-4-nitrophenolate sodium is preferably adjusted with the mineral acid. It is preferred to use a mineral acid which contains 3-methyl-4-nitrophenol to adjust the pH. The adjustment of the pH of the aqueous solution is advantageously carried out in the presence of an antifoam. It breaks up the foam formed by the reaction of the carbonate, e.g.

The process according to the invention yields 3-methyl-4-nitrophenol from waste products. The procedure is advantageous in those cases where it is not possible to obtain high-quality 3-methyl-4-nitrophenol sodium by crystallization. In particular, they are aqueous solutions in which the sodium 3-methyl-4-nitrophenolate concentration is below 2 wt. The process of the invention reduces the content of phenol derivatives in effluents. An example of an enyl / thiophosphate

To a three-necked flask equipped with a stirrer, a thermometer and a separating funnel, 500 ml of toluene, 75 g of 76.2 wt. Sodium 3-methyl-4-nitrophenolate and 10 g KgCO3. Zmessa warmed to a gentle boil. By dividing treatment, 180 ml of 30.5 wt. of a toluene solution of 0,0-dimethylchlorothiophosphate. The reaction mixture was kept at low boiling for 6 hours.

Claims (3)

After completion of the reaction, 200 ml of 80 ° C water was added to the reaction mixture to dissolve the crystalline salts. The toluene layer was separated from the aqueous; The aqueous layer contained 11.3 g of 3-methyl-4-nitrophenolate sodium, 0.06% by weight. of organically bound phosphorus and 0.05 wt. organically bound sulfur. Example 2 Example 1 was followed except that an aqueous layer from the previous experiment was added to the reaction mixture instead of water. The procedure was repeated six times. It obtained a savory solution containing 54.2. g of 3-methyl-4-nitrophenol. The solution was cooled to 10 ° C while sodium 3-methyl-4-nitrophenolate crystallized out. The mother liquor contained 2.6 wt. Sodium 3-methyl-4-nitrophenolate. From the solution, 3-methyl-4-nitrophenol was precipitated by the addition of hydrochloric acid 10% by weight, the pH of the aqueous layer being 3.1. The precipitated 3-methyl-4-nitrophenol was filtered off. 88.9 g of 51.6 wt. 3-methyl-4-nitrophenol. The filtrate contained 0.05 wt. % organic bound phosphorus and 0.05 wt. organically bound sulfur. Example 3 Example 2 was followed except that the solution was not allowed to cool to 10 ° C, but 3-methyl-4-nitrophenol was precipitated from the solution at a temperature of 70 ° C by adjusting the pH value to 4.6 with 10.3 wt. HgSO. containing 1,480 mg / l of 3-methyl-4-nitrophenol. The solution was then allowed to cool to 10 ° C and the precipitated 3-methyl-4-nitrophenol was filtered off. Acquisition of 8.1 g of 51.4% by wt. 3-methyl-4-nitrophenol. EXAMPLE 4 The procedure of Example 3 was followed except that the foaming of the carbonates by the carbonate decomposition was reduced by the addition of 0.01 g of polydimethylsiloxane-based defoamer (Lukosan S). The pH after precipitation was 1.4. The precipitated 3-methyl-4-nitrophenol was filtered from the suspension. 8.0 g of 52.3 wt. 3-methyl-4-nitrophenol. Obtained 3-methyl-4-nitrophenolmal Purity 99.6 wt. The invention is useful in the preparation of 3-methyl-4-nitrophenol, using an aqueous solution of 3-methyl-4-nitrophenol sodium in the production of O, O-dimethyl-O- (3-methyl-4-nitrophenyl) thiophosphate. SUBJECT MATTER 1. A method of isolating 3-methyl-4-nitrophenol from an aqueous solution of 3-methyl-4-nitrophenol sodium containing as inorganic salts, organic compounds of phosphorus, sulfur or chlorine, residues of aromatic solvents from the production of 0,0-dimethyl-O- ( 3-methyl-4-nitrophenyl) thiophosphate, characterized in that 3-methyl-4-nitrophenol is precipitated from the aqueous solution by adjusting the pH to 1 to 6 with mineral acid and the precipitated 3-methyl-4-nitro-phenol is removed from the aqueous solution. aqueous solution and impurities. 2. Process according to claim 1, characterized in that a mineral acid containing 3-methyl-4-nitrophenol is used as the impurity to adjust the pH. 3. Process according to claim 1, wherein the adjustment of the pH of the aqueous solution of 3-methyl-4-nitrophenolate sodium is carried out in the presence of an antifoam.