CS254208B1 - Method of n-cyclohexylthiophthalimide production - Google Patents

Abstract

The present invention relates to a process for the preparation of N-cyclohexylthiophthalimide, a high potency inhibitor vulcanization, by reacting cyclohexylsulfenyl chloride, dissolved in an inert solvent with an aqueous alkali salt solution phthalimide, which is formed directly in the reaction of the mixture by adding alkali hydroxide to phthalimide suspension in advance pre-introduced cyclohexylsulfenyl chloride solution. This bypasses Preparation of anhydrous alkali metal salt of phthalimide needed to prepare N-cyclohexylthiophthalimide.

Description

(54) Method of producing N-cyclohexylthiophthalimic acid

The present invention relates to a process for the preparation of N-cyclohexylthiophthalimide, a high potency vulcanization inhibitor, by reacting cyclohexylsulphenyl chloride dissolved in an inert solvent with an aqueous solution of the phthalimide alkali salt formed directly in the reaction mixture by adding the alkali hydroxide to the phthalimide suspension in advance. This avoids the preparation of the anhydrous alkaline salt of phthalimide, which is still needed in the preparation of N-cyclohexylthiophthalimide.

284208

The invention relates to a process for the preparation of N-cyclohexylthiophthalmide by reacting potassium and / or sodium phthalimide with cyclohexylsulphenyl chloride in the presence of water and / or aqueous potassium and / or sodium chloride solution.

N-Cyclohexylthiophthalimide is a high performance vulcanization inhibitor used in combination with the benzethiazole-type vulcanization accelerators suitable for synthetic and natural rubbers.

Known methods for producing N-cyclohexylthiophthalimide are based either on the reaction of cyclohexylsulfenyl chloride with phthalmide in the presence of an organic base as a hydrogen chloride binding agent or on the reaction of cyclohexylsulfenyl chloride with an anhydrous potassium salt of phthalimide. Thus, the preparation of N-cyclohexylthiophthalimide from cyclohexylsulphenyl chloride, which is previously prepared from cyclohexanethiol and chlorine in a carbon tetrachloride medium, is described and added to a suspension of phthalimide in a solution of triethylamine in carbon tetrachloride (USP No. 3,547,185). After separation of the triethylamine hydrochloride, the organic layer is concentrated and n-heptane is concentrated, and the expected product is precipitated with n-heptane.

In a similar manner, other patents describe the preparation of N-cyclohexylthiophthalimide (French Patent No. 1,500,844, British Patent No. 1115,214). The preparation of N-cyclohexylthiophthalimide by the reaction of cyclohexylsulfenyl chloride and the phthalimide potassium salt dissolved in suitable anhydrous polar solvents mixed with a non-polar solvent in which cyclohexylsulfenyl chloride is prepared is the subject of the present invention (AO No. 178 735).

Also described is a process for the preparation of N-cyclohexylthiophthalimide which uses dicyclohexyl disulphide and potassium phthalimide as the starting material (AO No. 191 385), to which it is treated with chlorine in a non-polar organic solvent and the resulting cyclohexylsulphenyl chloride is reacted with potassium phthalimide potassium.

The preparation of N-cyclohexylthiophthalimide from cyclohexylsulfenyl chloride and phthalimide in the presence of triethylamine, in a carbon tetrachloride environment (USP No. 3,547,185) has the major disadvantage that trietvlamine hydrochloride must be washed out of the reaction medium with water, recovered and dried.

It is even more disadvantageous if a solution of phthalimide and trietvlamine in dimethylformamide (French Pat. No. 1,500,844) is used to react cyclohexylsulfenyl chloride with phthalimide, since the recovery of triethylamine and dimethylformamide from aqueous solution is even more difficult.

A major disadvantage of other processes (AO No. 178 735 and AO No. 191 385) is that anhydrous potassium phthalimide is required to produce N-cyclohexyltinphthalimide, which is only very difficult and expensive to prepare. The quality of potassium phthalimide is very high. it is highly dependent on the manner in which it is prepared and, moreover, it significantly affects the quality and yields of N-cyclohexylthiophthalimide.

The above-mentioned disadvantages of the prior art are eliminated by the invention, which consists in the fact that the prepared solution of cyclohexylsulphenyl chloride in an organic solvent with a concentration of 5 to 20 wt. is added with a 1- to 40% potassium and / or sodium hydroxide solution to a suspension of phthalimide in water and / or in a solution of alkaline chlorides (potassium and / or sodium, and / or an inert organic solvent for 10 to 120 min. wherein the resulting alkaline phthalimide salt is reacted with cyclohexylsulfenyl chloride to form N-cyclohexylthiophthalimide.

By studying the reaction conditions of cyclohexylsulfenyl chloride in an organic solvent solution with phthalimide, a significant effect of the temperature and time interval between the dosing of the cyclohexylsulfenyl chloride solution and the aqueous alkaline hydroxide solution was found. In view of the reaction itself, an initial concentration of the alkali salt of phthalimide is required, the existence of which in the presence of water is strongly temperature-dependent. As the temperature rises, the competitive reaction of the hydrolysis of the phthalimide alkali salt to form the phthalic acid alkali salt also increases.

As has been shown, the optimum temperature for carrying out the reaction is 0 to 10 ° C, the interval between the start of the addition of the potassium hydroxide solution as the first component and the cyclohexylsulphenyl chloride solution is in the range of up to 30 min, preferably 3 to 12 min. min.

The molar ratio of phthalimide to cyclohexylsulfenyl chloride should be 0.95 to 1.3, preferably 1.0 to 1.02. An increase in the molar ratio above 1.02 results in an increase in the organic matter content of the aqueous filtrate solution.

The field of application of the invention is mainly in the process of producing N-cyclohexylthiophthalimide, respectively. other Ν-alkyl-, N-arylthiophthalmides, as an important rubber chemical for the processing of synthetic and natural rubbers.

The following examples illustrate but do not limit the scope of the invention.

Example 1

To a stirred suspension of 18.54 g (0.126 mole) of phthalimide in 66 g of 18% w / v potassium chloride solution was added 25.25 g (0.126 mole) of aqueous potassium hydroxide solution with cooling at 0 ° C. 141.5 g (0.132 conc. 14.04 wt.%), at a rate of 1.01 g.min ^-1 , with a 6 minute delay to the mole hydroxide solution) of the cyclohexylsulfenyl chloride-potassium solution. at the rate of 5.66 g.min ^-1 After the two components are dispensed, the reaction mixture is kept under vigorous stirring for 1 hour at room temperature, then heated to reflux, filtered and separated from the organic phase, after distillation of the solvent by crystallization from of cyclohexane gave 31.75 g of N-cyclohexylthiophthalimide, m.p. 91.5-93 ° C, corresponding to a 96.4% yield calculated on cyclohexylsulfenyl chloride.

Example 2

To suspensions of 78.5 kg (0.534 kmole) of phthalimide in 267 kg of a 14% aqueous potassium chloride solution cooled to 3-5 degrees Celsius, 122 kg of a 25% strength solution are started to be charged while cooling, with the already aqueous potassium hydroxide solution. (0.546 kmole) at 4.9 kg. min. ¹ (3.98.10 ³ m ³ min. ¹ ) and after 4 to 5 min. from the start of dosing of the potassium hydroxide solution · 538 kg of a 15.7% solution of cyclohexylsulfenyl chloride (0.562 kmol) in carbon tetrachloride, at a rate of 21.52 kg. min. ¹ . After both components were added, the reaction mixture was stirred for 45 min. Warm to reflux for 25 min. and the hot solution was filtered and after separating the organic layer and distilling off the carbon tetrachloride, 135.51 kg of N-cyclohexylthiophthalimide was obtained by crystallization from cyclohexane, corresponding to a 97.1% yield calculated on the starting phthalimide.

Example 3

To suspensions of 73.56 g (0.5 mol) of phthalimide in 210 ml of water cooled to 5-7 ° C, 90.91 g of 22% sodium hydroxide solution are added at a rate of 4.55 with cooling and vigorous stirring. g.min. ” ¹ (3.65.10 ³ min. ¹ ) and after 6 to 8 min. from the start of the feed of sodium hydroxide solution was 513.8 g The feeds of 13.33% -nélio · (wt.) solution (0.455 móluj cyklohexylsulfenylchloridu in carbon tetrachloride at a rate of 25.69 g. min. ^1st

After the addition of both components, the reaction mixture is stirred at room temperature for 2 hours, and finally heated to 50-55 ° C with stirring for 15 minutes, the hot reaction mixture is filtered a. After separating the organic layer and distilling off the carbon tetrachloride under reduced pressure, 108.5 g of N-cyclohexylthiophthalimide having a melting point of 91 DEG-93 DEG C., corresponding to a yield of 91.4% calculated on cyclohexylsulphenyl chloride, are obtained by crystallization from cyclohexane.

Claims (3)

SUBJECT Process for the preparation of N-cyclohexylthiophthalimide, characterized in that an aqueous solution of potassium and / or sodium hydroxide and a solution of cyclohexylsulphenyl chloride in an inert organic solvent are added to a suspension of phthalimide in water and / or an aqueous solution of potassium chloride and / or sodium chloride and / or an inert organic solvent. of the solvent, while the addition of both solutions ensures a timely addition of the solution OF THE INVENTION alkali hydroxide in the range up to 30 min. and the moles of solution addition rate of both components. min. ¹ is given by the ratio of 1: N, where N is the molar ratio between phthalimide and the total amount of cyclohexylsulfenyl chloride added in the range of 1 to 0.95 to 1.3 while maintaining the temperature of the reaction mixture at -10 to 70 ° C, preferably 0-10 ° C.