US2722554A - Preparation of high molecular weight wax thiols - Google Patents

Description

1 2,722,554 PREPARATION OF HIGH MOLECULAR WEIGHT WAX THIOLS Ferdinand P. Otto, Woodbury, N. J., assignor to Socony Mobil Oil Company, End, a corporation of New York No Drawing. Application January 17, 1952, Serial No. 267,008 3 Claims. (Cl. 260609) This invention relates to the preparation of organic sulfur-containing compounds. It is more particularly concerned with the production of high molecular weight alkyl thiols.

As is well known to those familiar with the art, many methods for the production of organic thiols have been proposed. Generally, it has been proposed to prepare such compounds by reacting halogenated hydrocarbons with inorganic hydrosulfides, such as sodium or potassium hydrosulfide. Such processes have been disadvantageous from a number of standpoints. They have been diflicult to control, permitting many undesirable side reactions. More significantly, and as a result of the foregoing, yields have been relatively poor.

High molecular weight thiocyanates, such as wax thiocyanates, have been likewise difficult to produce in good yields. It has been proposed to produce them by renited States PatentO acting the alkyl halide with a thiocyanate salt, such as sodium thiocyanate and the like. It has been found that yields in that method can be greatly improved by using a specific solvent combination. As discussed hereinafter, the novel process for preparing thiocyanates is one step of the present process for producing thiols. As is well known to those familiar with the art, high molecular weight thiocyanates and thiols have a wide variety of applications. They are intermediates for organic syntheses, oil addition agents, etc.

It has now been found that organic thiols can be prepared by a process which affords excellent yields and which involves a minimum of side reactions. It has now been discovered that high molecular weight alkyl thiols can be produced in good yield by a simple, threestep process; one step of Which process is in itself believed to be novel and patentable.

Accordingly, it is an object of the present invention to provide organic thiols by a process which involves a minimum number of side reactions. Another object is to provide a feasible process for the production of high molecular Weight alkyl thiols. A specific object is to provide a process for producing wax thiols in excellent yields and with a relatively small number of side reactions. A further specific object is to provide a simple method for producing wax thiocyanates in good yields and in a high degree of purity. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description.

Broadly stated, the present invention involves the process for producing high molecular weight alkyl thiols, which comprises reacting a high molecular 'weight alkyl monoor di-halid with an inorganic thiocyanate salt to produce a high molecular weight monoor di-thiocyanatc, converting this thiocyanate to a high molecular weight disulfide or tetrasulfide, and reducing the disulfide or tetrasulfide to the thiol.

PREPARATION OF THE THIOCYANATES In general, any alkyl halide or di-halide, or mixtures of such alkyl halides, containing more than about twenty carbon atoms, and preferably between about 21 and about 34 carbon atoms, per molecule can be used to prepare the thiocyanates by the process of this invention. The, alkyl radicals of these alkyl halides can bestraight-chain or branched-chain. Especially preferred are the high molecular weight alkyl chlorides, particularly Wax monoand dichlorides. Non-limiting examples of the alkyl halides contemplated herein are heneicosyl chloride; docosyl chloride; tricosyl bromide; 2-methyltricosyl chloride; tetracosyl dichloride; isohexacosyl chloride; triacontyl dibromide; tetratricontyl chloride; paraflin wax chloride; and parafiin wax dichloride.

As is well known to those familiar with the art, it is difiicult and not commercially feasible to produce these alkyl chlorides in a relatively pure state. A practical method for obtaining satisfactory mixtures of them is by partial chlorination of a wax melting between about 40 C. and about 72 C., such as paraflin wax, ozokeiite, ceresin wax, slack wax, and scale wax. The chlorination of such waxes results in mixtures of monochloro waxes and polychloro waxes. Accordingly, the monochloro waxes, dichloro waxes, and mixtures thereof must be separated from the chlorinated wax mixture. A suitable method for the chlorination of wax and the separation of monochloro and dichloro wax has been fully described in United States Letters Patent No. 2,238,790 to Davis et al., to which patent reference should be made.

Any inorganic salt of thiocyanic acid may be reacted with the alkyl halide reactant to produce the alkyl monothiocyanates. Sodium thiocyanate, strontium thio cyanate, potassium thiocyanate, and ammonium thiocyanate may be mentioned by Way of non-limiting examples.

The reaction between the inorganic salt reactant and the alkyl halide reactant can be eifected by refluxing a mixture of the chloro wax reactant and an excess of the inorganic salt reactant in a suitable solvent, at a temperature of about 130 C. for between about 5 hours and about 25 hours.

- The solvent utilizable herein is an alcohol solvent combination in which the inorganic salt reactant is soluble and which has a relatively high reflux temperature. The preferred combinations of alcohols comprise (1) a low molecular weight alcohol, such as methanol, ethanol, the propyl alcohols, and the butyl alcohols, and (2) higher molecular weight alcohol,- such as the amyl alcohols, the hexyl alcohols, and the octyl alcohols. The relative amount of each alcohol in the combination will be that sufiicient to produce a combination which refluxes at pot tern per'atures of about 100 C. or higher. In general, the proportions of the alcohols will vary between about 10 per cent and 50 per cent of the lower alcohol and between about 50 per cent and about 90 per cent of the higher alcohol, by volume. Non-limiting examples of alcohol combinations utilizable herein are 40 per cent isopr0panol- 60 per' cent fusel oil; 15 per cent ethanolper cent octanol; 10 per cent ethanolper cent fusel oil; 20 per cent methanol-80 per cent hexanol; and 50 per cen't'tbutanol-SO per cent amyl alcohol.

' When the high molecular weight alkyl thiocyanates and dithiocyanates are produced by the methods described hereinbefore, product separation is easily effected. The solvents can be removed by well-known methods, such as by evaporation or distillation. The unreacted organic thiocyanates and the inorganic halide formed during the reaction can be removed by filtration. The reaction product thus isolated is in a substantially pure form and is entirely satisfactory for further treatment in accordance with theprocess of this invention. In the manner aforedescribed, from alkyl monohalides will be obtained the corresponding alkyl thiocyanate; and from the dihalide will be obtained an alkyl dithiocyanate.

PREPARATION OF THE DI- AND TETRA-SULFI DES P atented Nov. 1, 1955 thiocyanate with alcoholic alkali-metal hydroxide, in accordance with the equations:

KCNO 1120 KOH K20 03 NHa In the foregoing equations, R'represents an alkyl group as aforedefined. When operating with an alkyl monothiocyanate, in accordance with Equation 1, an alkyl disulfide .-is produced. This subsequently is converted to an alkyl thiol .by the present process. In accordance with Equation .2, an alkyl dithiocyanate is changed to a compound having two disulfide linkages. This compound is called a tetrasulfide herein. It ultimately produces an alkyl d-ithiol by the process of this invention.

Any alkali-metal hydroxide can be used to prepare the alcoholic solution employed herein. Sodium and potassium hydroxides are preferred, however. The concentration of the alkali-metal hydroxide should be between about 5 :and about 25, preferably about 15. The solution .is prepared simply by dissolving the alkali-metal ,hy droxide in a suitable amount of a lower alcohol, such as ethanol, methanol, propanol, and isopropanol.

The alcoholic solution of alkali-metal hydroxide is reacted with the alkyl thiocyanate at the reflux temperature of .the alcoholic alkali solution, i. e., between about 80 C. and about 150 C.; for a period of time varying between about 2 hours and about hours. The reaction proceeds smoothly under these conditions. However, agitation of the reaction mixture is preferred.

Since the alkyl disulfides and tetrasulfides contemplated herein are soluble in hydrocarbons, separation of .the products is readily effected. Usually between about 50 to 100 per cent, by volume of the reaction mixture, of a relatively volatile hydrocarbon solvent is added to the reaction mixture. Suitable solvents are petroleum ether, benzene, toluene, xylene, Stoddards solvent, and the like. The resultant solution of alkyl disulfide and/or tetrasulfide ,is then washed with water to remove inorganic by products. It must be noted that potassium cyanide is one of the by-products. Suitable precautions should be taken accordingly. The washed solution is .dried and topped free from solvent, preferably under reduced pressure. The product, thus isolated, will be substantially pure alkyl disulfide and/or tetrasulfide, depending upon the alkyl thiocyanate which has been acted upon.

PREPARATION OF 'TI-HOLS The alkyl disulfide and/or tetrasulfide is converted to the corresponding thiol or dithiol by any of the methods known to the art for the reduction of organic compounds. The method utilized herein was reduction with nascent hydrogen produced by reacting zincand hydrochloric acid. In carrying out the reduction it is preferred to use an alcohol solvent, such as butanol, methanol, ethanol or pro-- panol. The zinc is preferably in the form of zinc dust, although other physical forms can be used. As will be recognized by those skilled in the art, instead of zinc and hydrochloric acid, other metal-acid combinations which release nascent hydrogen can be employed, e. g., tin and iron with hydrochloric or sulfuric acid. The reduction can also be efiected .catalytically, preferably using a -cata-' lyst which is not poisoned by sulfur, e. g, molybdenum sulfide,- or using molybdena or chromia under high hydrogen pressures.

The reduction reaction proceeds smoothly at tempera-= tures of between about 70 C. and about 100 C. It is complete in between about one hour and about 5 hours, depending, of course, on the temperatures employed. The thiol product is isolated by dissolving it in alight hydrocarbon solvent, suchas is used for the disulfides, and wa- 4 ter washing the solution free of acid. The unused zinc, or other metal, -is removed by decantation or -by filtration methods. The washed product is topped free of solvent, leaving a relatively pure alkyl thiol. It has been found that by following the present procedure, about 80 per cent of the thiocyanate is converted to a thiol which is remarkably free from side-reaction products.

'The following specific examples are given solely to exemplify the process of this invention. It is to be strictly understood that this invention is not to be limited to the particular alkyl halides, wax chlorides, and other reactants employed, or to the'operations and manipulations involved. Other reactants and conditions, as described hereinbefore, can .be used, .as those skilled in the art will readily appreciate.

Example 1.Preparati0n 0f chloro waxes One thousand .grams .of a paraflin wax, having a melting point .of about 52 C., were heated to 85 C. Chlorine gas was .passed into the resulting melt until the wax gained about 111 grams in weight. The reaction mixture was then .blown with nitrogen ,gas to remove occluded hydrogen chloride and residual chlorine, producing a product which contained about ten per cent of combined chlorine by weight. This product was allowed to stand for about 17 hours (overnight), at a temperature of 2330 C. The unreacted paraflin wax solidified and the chlorinated parafl'l-n wax remained liquid at these temperatures. Separation of the two phases was effected by filtration. Then, a 570 gram portion of the filtrate, consisting, in the main, of monochloro and dichloro wax, was dissolved in ten times its volume of acetone, .and the resulting solution was chilled to 23 C. The monochloro wax, which precipita-ted at this temperature, was removed by filtration and topped at 150 C. under a pressure of about 150 millimeters .to remove entrained solvent. The monochloro wax, which was obtained in a 55 percent yield, contained 9.5 per cent chlorine. The filtrate containing predominantly dichloro wax was freed of acetone by distillation under reduced pressure. The dichloro wax fraction contained 19.3 per cent chlorine.

WAX MONOTHIOL Example 2.Preparati0n of wax monothiocyanate A mixture of 400 grams of a monochloro wax containing 10.5 per cent chlorine, prepared as described in Example l, grams of ammonium thiocyanate, 350 cubic centimeters of fusel oil, and 350 cubic centimeters of butanol-l was stirred and refluxed for about twenty hours at 130 C. The ammonium chloride which formed as a result of the ensuing reaction between the monochloro wax and the ammonium thiocyanate, was removed by filtration. The solvents were removed from the filtrate by distillation at -C. under reduced pressure. After cooling the residue to room temperature, unreacted ammonium thiocyanate was removed by filtration leaving relatively pure wax monothiocyanate. This was a light orange oil, that became a waxy solid on standing, and which contained 7.58 per cent sulfur, 3.2 per cent nitrogen, and 0.53 per cent chlorine.

Example 3 .-Preparation of wax disulfide A mixture of 75 grams of the wax monothiocyanate of Example '2 and a solution of 20 grams of potassium hydroxide in 150 cubic centimeters of butanol-l was placed in a reaction vessel and agitated for 6 hours at about 114 C. As the reaction proceeded, a white precipitate formed on the walls of the reaction vessel and ammonia was mildly evolved. Then, the reaction mixture was diluted with about 75 cubic centimeters of benzene and washed with water, until the washings were neutral. The washed mixture was topped at 150 C. under diminished pressure. The product, an orange-brown waxy material, contained 6.7 per cent sulfur, 0.45 per cent nitrogen, and had amolecularweight of 606.

5 Example4 To a mixture of 53 grams of wax disulfide from Example 3, 200 cubic centimeters of concentrated hydrochloric acid, and 75 cubic centimeters of butanol-l were added, gradually and with agitation, 100 grams of zinc dust. After the addition of the zinc dust was complete, the temperature was gradually raised to 90100 C. After heating the mixture for three hours at this temperature, the rate of evolution of hydrogen decreased materially. Then, 75 cubic centimeters additional concentrated hydrochloric acid were added, and the reaction was continued for three hours more. The mixture was cooled and diluted with 100 cubic centimeters of benzene. The liquid layer was decanted from the unreacted zinc. After water washing to remove the hydrochloric acid, the product was topped at 150 C. under reduced pressure. The wax thiol product was a white waxy solid at room temperature, containing 6.1 per cent thiolic sulfur and having a molecular weight of 387.

MIXED WAX MONO- AND DI-THIOL Example 5 .Preparation of mixed wax monoand di-thiocyanates A mixture of 875 grams of 11 per cent chlorowax, 380 grams ammonium thiocyanate, 800 cubic centimeters of fusel oil, and 800 cubic centimeters of butanol-l was placed in a reaction vessel equipped with mechanical stirring means. The chlorowax was a paraffin wax which had been chlorinated to the extent of 11 per cent chlorine content and which was free of unchlorinated wax. This wax is a mixture of monoand di-chlorowax. The reaction mixture was agitated and heated at reflux for 23 hours at a temperature of about 128 C. Then, the ammonium chloride formed during the reaction was removed by filtration and the mixture was topped at a temperature of 150 C. After the topped product was cooled, the ammonium thiocyanate, which had been dissolved in the alcohol solution, was filtered 01f. The light orange oil which turned to a waxy solid upon standing was a mixture of wax monoand di-thiocyanate. It contained 9.9 per cent sulfur and 4.3 per cent nitrogen, by weight.

Example 6.Preparatin of wax diand tetra-sulfide A mixture of 400 grams of the mixed wax thiocyanates of Example 5, and a solution of 104 grams of potassium hydroxide in 600 cubic centimeters of butanol-l was refiuxed for 8 hours at 116 C. The reaction mixture was then diluted with about 400 cubic centimeters of benzene and water washed. The washed product was topped at 150 C. under reduced pressure. The product was a mixture of wax disulfide and wax tetrasulfide. It contained 8.9 per cent sulfur.

Example 7.--Preparati0n of wax monoand di-thiols To a mixture of 315 grams of the wax sulfides of Example 6, 300 cubic centimeters of butanol-l, and 800 cubic centimeters of concentrated hydrochloric acid were added, gradually and with agitation, 400 grams of zinc dust. After the addition of zinc dust was complete (about 1 /2 hours), the temperature of the reaction mixture was slowly raised to 100 C. After about three hours, the brisk evolution of hydrogen had subsided. Then, 75 cubic centimeters additional of concentrated hydrochloric acid were added, and heating was continued for three hours more. The resultant mixture was diluted with about 300 cubic centimeters of benzene, decanted from the unreacted zinc, and water washed free of acid. The solvents were removed by topping at 160 C. under reduced pressure. The product, a light yellow waxy material, contained 8.1 per cent thiolic sulfur.

The foregoing examples have illustrated the preparation of wax thiols by the process of this invention. The nethod of producing high molecular weight alkyl thiovanates has also been illustrated, as a necessary subcombination of the main process. As will be appreciated by those skilled in the art, alkyl thiols other than wax thiols can be produced with a high degree of purity and in good yields by the present method. Thus, the method is generally applicable to produce any alkyl thiol. It is, however, most useful for preparing thiols having 21 or more carbon atoms per molecule. It is in the production of these compounds by other processes that more difiiculties with side reactions, low yields, and poor quality are encountered.

Although the present invention has been described in conjunction with preferred embodiments, modifications and variations are contemplated, as those skilled in the art will readily understand. Such variations and modifi cations are considered to be within the purview and scope of the appended claims.

This application is a continuation-in-part of copending application Serial Number 83,522, filed March 25, 1949, now Pat. No. 2,619,464, by the present inventor, and of Serial Number 191,927, filed October 24, 1950, now Pat. No. 2,680,759, a division of Serial Number 83,522.

What is claimed is:

1. The process for producing high molecular weight wax thiols, which comprises converting a wax thiocyanate selected from the group consisting of (l) wax monothiocyanates, (2) wax dithiocyanates to the corresponding wax polysulfide selected from the group consisting of (1) wax disulfides, (2') wax tetrasulfides and (3') mixtures of said wax disulfides and said wax tetrasulfides with an alcoholic solution of an alkali-metal hydroxide, at a temperature varying between about C. and about 150 C., for a period of time varying between about 2 hours and about 10 hours; and reducing said corresponding wax polysulfide to the wax thiol with nascent hydrogen produced by reacting a metal with an inorganic acid, at a temperature varying between about 70 C. and about C., and for a period of time varying between about 1 hour and about 5 hours.

2. The process for producing wax monothiols, which comprises converting a wax thiocyanate to the corresponding wax disulfide with an alcoholic solution of potassium hydroxide, at a temperature varying between about 80 C. and about C., for a period of time varying between about 2 hours and about 10 hours; and reducing said corresponding wax disulfide to the wax thiol with nascent hydrogen produced by reacting zinc with hydrochloric acid, at a temperature varying between about 70 C. and about 100 C., and for a period of time varying between about 1 hour and about 5 hours.

3. The process for producing wax thiols, which comprises converting a mixture of wax monothiocyanate and wax dithiocyanate to the corresponding mixture of wax disulfide and wax tetrasulfide with an alcoholic solution of potassium hydroxide, at a temperature varying between about 80 C. and about 150 C., for a period of time varying between about 2 hours and about 10 hours; and reducing said mixture of wax disulfide and wax tetrasulfide to the mixture of wax thiol and wax dithiol with nascent hydrogen produced by reacting zinc with hydrochloric acid, at a temperature varying between about 70 C. and about 100 C., and for a period of time varying between about 1 hour and about 5 hours.

References Cited in the file of this patent UNITED STATES PATENTS Chemie, vol. 3, 4th ed. (1921), p. 175.

Richter, Organic Chemistry, vol. 1, page 525 (3rd ed.) (1944), Elseverier Publ. Co., New York, N. Y.

Claims (1)

1. THE PROCESS FOR PRODUCING HIGH MOLECULAR WEIGHT WAX THIOLS, WHICH COMPRISES CONVERTING A WAX THIOCYANATE SELECTED FROM THE GROUP CONSISTING OF (1) WAX MONOTHIOCYANATES, (2) WAX DITHIOCYANATES TO THE CORRESPONDING WAX POLYSULFIDE SELECTED FROM THE GROUP CONSISTING TO (1'') WAX DISULFIDES, (2'') WAX TETRASULFIDES AND (3'') MIXTURES OF SAID WAX DISULFIDES AND SAID WAX TETRASULFIDES WITH AN ALCOHOLIC SOLUTION OF AN ALKALI-METAL HYDROXIDE, AT A TEMPERATURE VARYING BETWEEN ABOUT 80*C. AND ABOUT 150*C., FOR A PERIOD OF TIME VARYING BETWEEN ABOUT 2 HOURS AND ABOUT 10 HOURS; AND REDUCING SAID CORRESPONDING WAX POLYSULFIDE TO THE WAX THIOL WITH NASCENT HYDROGEN PRODUCED BY REACTING A METAL WITH AN INORGANIC ACID, AT A TESMPERATURE VARYING BETWEEN ABOUT 70*C. AND ABOUT 100*C., AND FOR A PERIOD OF TIME VARYING BETWEEN ABOUT 1 HOUR AND ABOUT 5 HOURS.