DE1935302C3 - Process for the production of isothiocyanates - Google Patents

Description

example 1

In a known manner, 12 moles of methylamine (= 930 g, 40% strength solution) are added to 12 moles of carbon disulfide (= 912 g) and 12 mol of NaOH (480 g), dissolved in 2 l of water and obtained after two hours a yellow-red color pure solution of the sodium salt of N-methyldithiocarbamic acid.

4 mol of cyanuric chloride (= 738 g) are suspended in 21 ice water in a 10 l flask. The solution of N-methyldithiocarbamic acid is allowed to run in with thorough stirring. The condensation takes place spontaneously with a weak heat tone and the temperature rises to 30 ^° C. After the condensation has ended, a descending condenser with a cold trap is placed on the round bottom flask. The cooler and the cold trap are heated ^{to 35 to 40 ° C. with warm water.} The reaction mixture is heated with stirring. At a temperature of 85 to 90 ⁰ C, the azeotrope HjO-methyl isothiocyanate distills off. In the cold trap

the components separate. The distillation will continued until the temperature in transition The methyl isothiocyanate layer has reached 100 ^{° C.} is now separated. It crystallizes immediately when

Cool down through. White crystals, m.p. 34 to 35 ° C Amount / 852 g, corresponding to 97.1% of the theoretical value Th.

In the residue of the reaction flask there are yellow crystals which are insoluble in water and which are filtered off with suction, washed and dried. Quantity: 701g. Analysis for C ₃ H ₃ N ₃ S ₃ :

Calculated: C 203, H 1.7, N 23.7, S 54.2; found: C 20.2. H 1.7, N 23.4, S 53.9.

The analysis shows that the residue is 2,4,6-tris-mercapto-s-triazine

Example 2

40 g of NaOH are dissolved in 100 ml of H ₂ O, 76 g of carbon disulfide are added and 73 g of n-butylamine are slowly added dropwise with stirring into the mixture. Then it is heated to 40 to 45 ° C for two hours.

In a second stirred vessel, 61.5 g of cyanuric chloride are dissolved in 300 ml of methylene chloride. The golden yellow solution of sodium n-butyldithiocarbaminate is allowed to run into this solution. The temperature rises to 40 ° C during this process. The heating is continued, the intermediate condensation product of cyanuric chloride with n-butyldithiocarbamic acid decomposing in an exothermic reaction. The temperature of the mixture reaches 60 ⁰ C. After two hours, the mixture is cooled down, the trimercaptotriazine formed is suction filtered and the filtrate is separated and the methylene chloride layer. This is dried and fractionated in vacuo. The n-butyl isothiocyanate distills off at a Kpi2 61 ° C. Quantity: 102 g = 88.8% of theory

Example 3

A solution of 1 mole of potassium phenylethyldithiocarbamic acid (= 235.1 g) in 500 ml of water is added dropwise with stirring to a solution of 61.5 g of cyanuric chloride in 200 ml of chloroform. The reaction is initially slightly exothermic. When heated to 60 ^° C., a strongly exothermic reaction sets in. After two hours of heating, the mixture is cooled, the trimercaptotriazine is filtered off with suction, the chloroform layer in the filtrate is separated off and dried, filtered and fractionated. The phenylethyl isothiocyanate distills at bp ₅ 146 ° C. Quantity: 150.5 g = 92.3% of theory

Is obtained in the same manner from 221.1 g Benzyldithiocarbaminsaurem potassium and 61.5 g of cyanuric chloride in 200 ml of chloroform, 132.4 g of benzyl mustard (= 88.9% yield), bp 126 to 128 ° C _n.

Example 4

98 g of 2-methylmercapto-4,6-dichlorofiazine are dissolved in 250 ml of BenzoL A solution of 1 mol of N-methyldithiocarbamic acid is added dropwise with stirring Sodium (= 129 g) in 200 ml of water.

The reaction is slightly exothermic. The mixture is then heated to 70 to 75 ° C. (two hours) and cooled then off, sucks off, dries and distilled over ίο a small column.

At a boiling point of 117 to 119 ° C., 65.9 methyl isothiocyanate distill (= 90.2% of theory).

Example 5

111 g of n-butoxy-4,6-dichlorotriazine are packed in 200 ml Suspended water and added 200 ml of methyl ethyl ketone. A solution of 1 mol of sodium cyclohexyldithiocarbaminate in 300 ml of water is added dropwise The mixture heats up to 40 ° C. When heated 75 to 8O ⁰ C an exothermic reaction and the mixture begins to boil. This temperature is kept for one hour, then cooled, suction filtered and the filtrate extracted with methylene chloride. After drying with sodium sulfate, it is filtered and distilled

The cyclohexyl isothiocyanate distills at bp ₃ 99 ° C. Quantity: 121.4 g - 86.2% of theory

Example 6

A solution of sodium phenyldithiocarbaminate is prepared from 95 g of aniline, 80 g of carbon disulfide and 40 g of NaOH in 200 ml of H ₂ O, and this is added dropwise at 0 to 10 ° C. to a suspension of 61.5 g of cyanuric chloride in 250 ml of water. Then it is heated.

An exothermic reaction sets in at 60 to 70 ° C. The mixture is heated for one hour at 70 to 8O ⁰ C, then cooled, filtered with suction, the precipitate is washed out with methylene chloride and separated in the filtrate and the methylene chloride layer from this and works as described.

The phenyl mustard oil distills at bp _n 91 to 92 ° C. Quantity: 127.6 g = 94.4% of theory

Example 7

A solution of 2 mol of sodium ethyldithiocarbaminate in 250 ml of water is added dropwise to a dispersion of 193 g of 2-ethylamino-4,6-dichlorotriazine in 400 ml of ice water and then heated. At 70 to 8O ⁰ C an exothermic reaction starts. The heating is continued and ethylene mustard oil is distilled off together with water. The components are separated in the template. It is extracted with methylene chloride, dried and distilled.

C2H5NCS distilled ₁₈ 36 ° C. in Kp amount: 158.1 g = 90.7% of theory

Claims (1)

Claim: Process for the preparation of isothiocyanates of the formula (I) R-N = C = S in which R is an alkyl, cycloalkyl, aryl or aralkyl radical, the alkyl radical having 1 to 18 carbon atoms and optionally by the radicals —OR ¹ and / or —R ¹ , in which R ^{1 is} an alkyl radical having 1 to 12 Carbon atoms, monosubstituted or polysubstituted, and wherein the aryl radical can optionally be substituted one or more times by a bromine or chlorine atom or by an —OR ¹ or alkyl radical having 1 to 4 carbon atoms, characterized in that 1 mol a triazine compound of the formula (II) Cl I. c N N (II) Il I
ci-cc-x in which X stands for a -SR ² -, NHR ² group, in which R ² denotes an Aikylrest with 1 to 12 carbon atoms, or for a -OR ^J group, in which R ³ an Aikylrest with 1 to 12 carbon atoms or a , optionally substituted by halogen atoms or by an OR 'group, denotes, or denotes a chlorine atom, with 2 or 3 mol of a dithiocarbaminate of the formula (III) RNH-C-S-Me (III) where Me is alkali metal, ammonium or an alkaline earth metal, is reacted at a temperature of about 0 to about 5O ⁰ C in the presence of water as solvent or in the presence of a homogeneous or heterogeneous mixture of water and an organic solvent, the resulting bis or tris dithiocarbaminate of triazine, optionally decomposed by heating to a temperature of up to about 100 ° C., and the resulting mercaptotriazine-isothiocyanate mixture is separated by steam distillation or extraction. It is known that methyl isothiocyanates can be prepared by reacting N-methyldithiocarbaminates with chloroformic acid esters or with phosgene (DT-AS 68 250 and 1178 423). In these processes, carbon oxysulphite occurs as a by-product, which is a colorless, odorless, very poisonous gas. Therefore, special precautionary measures must always be observed during the synthesis. In addition, according to this process, the methyl isocyanate can only be obtained in pure form in yields of about 52% and ¹ in impure form only in yields of about 70%. All other known manufacturing processes, welehe are not limited to the production of the methyl derivative, could not be used in technology Find them because they are either too expensive in terms of the production of the starting materials or because they are only lead to low yields. This includes the ίο Manufactured by rearrangement of thiocyanic acid esters in the liquid phase or in the vapor phase (US-PS 29 54 393), the implementation of thiophosgene with Amines (J. Chem. Soc 125, 1702 [1924]) and the reaction of thiocarbanilides with hydrochloric acid (J. Am. Chem. Soc. 44, 2899 [1922]). It is also known the thiocarbaminates with POCI3 in the presence of to convert tertiary amines into isothiocyanates (Ber. 98 [1965] page 2425/26). This procedure is disadvantageous in that the tertiary amines have to be recovered. The invention now relates to the process defined in the claim which allows isothiocyanates to be produced in high yields and in pure form. In the process according to the invention, the thiocarbaminates of s-triazine are formed as intermediates especially with gentle heating quickly in 1 mol of the corresponding mercaptotriazine and 2 or 3 mol decompose of the isothiocyanate. The reaction can take place in water or in mixtures of water and an organic solvent, ie a 1- or 2-phase system. Examples of organic solvents are: ketones, simple or substituted hydrocarbons, methylene chloride, Chloroform, carbon tetrachloride, acetonitrile, ether, ester, nitrobenzene. The mercaptotriazines also obtained in the process, for example the 2-alkylmercapto-4,6-dimercaptc-s-triazines and the 2-alkoxy (phenoxy) -4,6-dimercapto-s-triazines are valuable by-products and can be used to make vulcanization accelerators or inhibitors. in the In contrast to carbon oxysulphide, they are non-toxic and can be handled without danger. The isothiocyanates can be used as starting materials for the production of other products, for example substituted ones Thioureas, can be used. They are also used as drugs, Nematicide, Fungicides and bacterial oids.