Patented May 19, 1953 2,639,267 UNITED STATES PATENT office 2,639,267 TEOCYANOGEN CONTAINING COMPOSITIONS Harry F. Pfann, Pittsburgh, Pa., assignor to Kop pers Compaay, Inc., Pittsburgh, Pa., a corpo ration of Delaware No Drawing. Application April 13, 1948, serial No. 20,840 Claims. (C. 252-182) 2 This invention relates to the manufacture of and thereupon treated with hydrogen peroxide as free thiocyanogen (SCN)2 and derivatives pre in the foregoing procedure. pared by the reaction of thiocyanogen with or in either of the above processes, the organic ganic compounds. compound to be reacted with the free thiocyano Heretofore thiocyanogen has been commonly gen may be added prior to the introduction of the made by treating either a metal thiocyanate with hydrogen peroxide or, the solution of free thio elemental bromine, or by reacting a metal thio cyanogen in the solvent may be added to the cyanate in Solution with copper sulfate to form organic compound which is to be thiocyanated. cupric thiocyanate which in turn is decomposed For most commercial processes, it is preferred to to produce free thiocyanogen. While both of prepare the solution of alkali thiocyanate and these processes are workable and yield free thio reactant organic compound in the solvent, and Cyanogen, they are subject to certain limitations. then add at a controlled rate the hydrogen per The reaction of elemental bromine with thiocya oxide which is to effect the liberation of the free nates is a costly process because of the expensive thiocyanogen. The rate of oxidation of the thio bronine which is required. The reaction of thi cyanic acid by the hydrogen peroxide should be ocyanates with copper Sulfate yields large quan such as to permit simultaneous reaction of the tities of the voluminous, insoluble precipitate of free thiocyanogen without the accumulation of cuprous thiocyanate from which separation of appreciable quantities of it. Such control of the the other desired reaction products is somewhat reaction will lead to the formation of thiocyano difficult. Because of these and other considera derivatives with a minimum of undesirable by tions, it is highly desirable to provide a more products such as perthiocyanic acid and related WOrkable and less expensive procedure for the compounds. preparation of free thiocyanogen. As a reaction medium there may be used any The primary object of the present invention is non-reactive liquid which is both a Solvent for to provide a process for the production of free the thiocyanic acid, or for the alkali thiocyanate thiocyanogen from inexpensive raw materials , if it is used, and also a solvent for hydrogen per and with the production of a minimurn of diffi oxide and the organic compound to be reacted Cultly handled co-products. upon. Examples of solvents whith are suitable Another object of this invention is to provide include methyl alcohol, ethyl alcohol, isopropyl a process for the production of free thiocyanogen alcohol, and tert.-butyl alcohol. Acetic acid may in such a medium that it may be readily reacted also be used, as may the lower fatty acid esters with Organic compounds to nake thiocyanogen such as ethyl acetate. Ether derivatives such as derivatives. dioxane and the methyl ether of ethylene glycol A further object of the invention is to provide or the ethyl ether of diethylene glycol are like a cyclic process for the production of free thio wise. Suitable. cyanogen in which process no co-products or by As an oxidizing agent, it is desirable to use products are formed which are not easily removed hydrogen peroxide of between 30 and 90% purity from the reaction medium in a simple cyclic sys in order to minimize the quantities handled and te. to minimize dilution of the reaction medium, I have now discovered that thiocyanogen may Hydrogen peroxide of higher concentration is be produced by using hydrogen peroxide as an 40 effective but at the present time it is relatively oxidizing agent to react upon thiocyanic acid or more expensive than the lower concentration upon solutions of thiocyanates in acid medium. products. Hydrogen peroxide of concentrations The reaction is presumed to proceed according to lower than 30% is workable, but involves the the following equation: 45 undesirable factor of great dilution of the reac tion mixtures. Suitable acids for reaction with the alkali thio. Accordingly, thiocyanic acid dissolved in a suit cyanates to form thiocyanic acid include sulfuric able reaction medium such as ethyl alcohol may and phospholic acid. Nitric acid may be used be treated with hydrogen peroxide to form free 50 under certain conditions, but it is generally de thiocyanogen and water. The reaction medium sired to avoid an acid possessing oxidizing prop should be acidic. erties when working in a medium containing Alternatively, a solution of a metal thiocyanate reactive organic compounds such as ethyl alcohol. dissolved in a solvent, may be made acid with a The halogen acids such as hydrochloric and strong acid such as sulfuric or phosphoric acid, 55 hydrobromic acid are normally to be avoided be 2,639,267 3 4 cause of their reactivity with hydrogen peroxide, inorganic salts or acids which are present in Control of the reaction temperature is impor Solutions of free thiocyanogen prepared by con tant. If the temperature is permitted to rise Ventional methods, was taken for reaction. With appreciably above 50° C., the rate of polymeriza a thiocyanogen acceptor as described in Example tion of free thiocyanogen to perthiocyanic acid 5 IV below. becomes excessive. At temperatures below 0° C. the rate of reaction of hydrogen peroxide with Eacample III thiocyanic acid is too low for practical purposes. For the production of thiocyano-meta-tolui Preferred temperatures are between 10° C. and dine, the following reactants were charged to a 30° C. O kettle in the order shown: The following reactive organic compounds can be treated With free thiocyanogen in order to Methanol ------500 prepare thiocyanogen derivatives: aromatic Sodium thiocyanate------48.5 amines Such as aniline and its homologs, includi Meta-toluidine ------26.7 Sulfuric acid, conc------510 ing ethyl aniline, diethyl aniline, butyl aniline, Acetic acid, glacial------50.0 dibutyl aniline, diphenyl amine, and substituted Hydrogen peroxide------68.0 anilineS Such as the chloro and nitro anilines; phenol derivatives such as the nitro phenols, Methanol ------4.0 chlorophenols, and ortho-cresol; hydroxyphenols The addition of the sulfuric acid caused the Such as resorcinol, catechol, pyrogallol, and 20 precipitation of the meta-toluidine sulfate. This phloroglucinol; unsaturated Organic compounds formed a heavy slurry which was diluted and Such as butadiene, isobutylene, vinylcyclohexene, partially dissolved with acetic acid. Over a styrene monomer, dicyclopentadiene, allyl chlo period of 2 to 3 hours there was added, in in ride, allyl alcohol, drying oils and their fatty Crements, the hydrogen peroxide which had been acids, and other olefinic compounds. In the 25 mixed with an equal volume of methanol. The Specification and claims the above listed con temperature of the reaction mixture was main pounds will be referred to as “thiocyanogen ac tained at 18-21° C. during the addition of most ceptors.' of the peroxide, and was finally permitted to rise Illustrative Of the processes Which may be used to 30° C. at the end of the reaction. The color to carry out the present reactions are the follow 30 of the mixture which had remained light during ing examples, which examples are given by Way the addition of most of the hydrogen peroxide, of illustration but are in no sense to be considered turned quite dark at the end when an excess of limiting as to the Scope of the present invention. free thiocyanogen was present. In the following examples all quantities represent The reaction mixture was poured into a large parts by Weight. Volume of Water made alkaline by the addition EaCample I of Sodium hydroxide, and the alkaline mixture To produce a Solution of free thiocyanogen in Was extracted once with benzene to recover the a mixture of alcohol and water, the following thiocyano-meta-toluidine. The benzene solu reactants were added in the indicated order to tion, after being treated with an adsorbent acti a Suitable vessel equipped for agitation and 4. vated carbon such as “Darco,' was filtered, and cooling. the benzene removed by distilation at reduced pressure to leave a residue of crude thiocyano Water ------150 meta-toluidine amounting to 74% of theory. Methanol ------100 After several recrystallizations from ethanol Sulfuric acid, concentrated.------25 45 Water mixtures a white crystalline product was Sodium thiocyanate-0.3 mole------25 obtained having a melting point range of 78-800 C. Hydrogen peroxide, 30%-0.27 mole------30 Eacample IV To the Solution of sodium thiocyanate in an alcohol-Water Solvent the Sulfuric acid WaS grad For the preparation of the thiocyanogen addi ually added with simultaneous cooling and agi 50 tion products of olefinic hydrocarbons and other tation. The resultant solution of thiocyanic acid thiocyanogen acceptors of limited Solubility in was cooled to 10° C. and the hydrogen peroxide polar solvents, it is desirable to Carry out the was then gradually added. The free thiocyanic reaction in an ether solution. For such cases acid was obtained as a clear orange-colored solu Solutions of free thiocyanogen, as prepared by tion in alcohol-water solvent. Preferably the 55 Example II, are used as the source of thiocyano. free thiocyanic acid may be used for reaction gen. Thus, to a solution of higher molecular with a thiocyanogen acceptor such as described Weight olefin such as decene-1 dissolved in car in Example IV below. In order to minimize the bon tetrachloride there is slowly added a solution polymerization of the thiocyanic acid to perthio of free thiocyanogen in ether. After allowing cyanic acid, the temperature of the reaction mix 60 Sufficient time for the reaction of the thiocyano. ture should be held at approximately 0° C. until it gen With the olefin, the reaction mixture is fil is used. tered for removal of any perthiocyanic which Eacample II may have formed. The dithiocyanodecane is then recovered by removal of the solvent by dis An aqueous solution of thiocyanic acid was 65 tilling at reduced pressure. mixed with ethyl ether so as to take up the thio This general technique may be applied with cyanic acid in ether. The ether was separated equal advantage to solutions of thiocyanogen ac from the aqueous phase and added to an amount ceptors in hexane, decahydronaphthalene, cyclo of anhydrous ethanol equivalent to One-third the hexane, ethylene dichloride, and similar classes Volume of ether Solution. To the ether thio 70 of compounds in which inorganic thiocyanates cyanic acid-ethanol solution was added a slight are insoluble. excess of 30% hydrogen peroxide which reacted The preferred form of the invention having With the thiocyanic acid in accordance with been thus described, what is claimed as new is: Equation I above. 1. A process for making a solution of thiocyano This solution of free thiocyanogen, without the 75 gen consisting essentially of reacting thiocyanic 2,639,267 5 6 acid and hydrogen peroxide in an acidic water between 0 and 60° C., said mutual solvent includi containing mutual organic solvent at a tempera ing ether and ethanol and said thiocyanic acid ture between 0 and 50° C. being incorporated in said mutual solvent in an 2. The process of claim 1 in which the mutual ether solution free of inorganic contaminents. solvent comprises a mixture of water and meth 6 HARRY F. PFANN. anol. 3. The process of claim 1 in which the thiocy References Cited in the file of this patent anic acid is formed in situ from a mineral acid UNITED STATES PATENTS and a salt of thiocyanic acid. 4. The process of claim 3 in which the mineral O Number Name Date acid is selected from the class consisting of Sul 2,212,175 Clayton et al. ------Aug. 20, 1940 furic and phosphoric acids. 2,312707 Fuchs ------Mar. 2, 1943 5. The process of claim 1 in which the thiocy 2,342,448 Bousquet ------Feb. 22, 1944 anic acid used is incorporated in the reaction 2,376,796 Mathes ------May 22, 1945 mixture in a solution consisting of thiocyanic acid 5 2,395,453 Bruson ------Feb. 26, 1946 and a solvent component of said mutual solvent. 2,395,455 BruSOn ------Feb. 26, 1946 6. The process of claim 5 in which the Solvent 2,399,361 Lacy et al. ------Apr. 30, 1946 component is diethyl ether. 2,411,869 Bruson ------Dec. 3, 1946 7. A process for making a solution of thiocyan 2,412,799 Bruson ------Dec. 17, 1946 ogen which comprises reacting thiocyanic acid 20 OTHER REFERENCES and hydrogen peroxide in an acidic water-con Williams: "Cyanogen Compounds,' second ed. taining mutual organic solvent at a temperature (1948), Edward Arnold & Co., London, page 310.