Patented Jan. 17, 1950 2,495,085 UNITED STATES PATENT OFFICE 2,495,085 EPREEPARATION OF SULFENAMDES Gien Alliger, Akron, Ohio, assignor to The Fire stone Tire & Ruibber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application September 7, 1946, Seria. No. 695,545 1. Claims. (C. 260-306.6) 1. 2 The present invention relates to the synthesis It is not only necessary to use a low temper of sulfenamides by a two-step process. In the ature-e.g., a temperature below about 10° C.- first step an aqueous suspension of a N-mono but high solution concentrations must also be em chloro primary amine is prepared by reacting a ployed. For commercial operations temperatures primary amine with an aqueous Solution of the Within the range of about 10° C. to about -20° hypochlorite of an alkali metal or an alkaline or -30° C. are satisfactory. The solution concen earth metal. The reaction is carried out at a trations must be so high that no more than a min iow temperature. In the second step an aqueous inal amount of the N-monochloro primary annine solution of an alkali metal or alkaline earth metal is in solution. In other Words, the concentrations mercaptide is nixed With the aqueous suspension O must be Such that substantially all of the N-mono of the N-monochloroamine resulting from the first chloro primary amine is precipitated from the step. Here again, a low temperature is used. In aqueous medium as an oil or solid (depending carrying out the process, a minimal amount of upon its melting point and the temperature em Water is used so that only a small amount of the ployed) So that the mercaptide reacts with the N-monochloro primary annine is in solution dur N-monochloro primary amine in an undissolved ing the reaction with the Suifeinamide, or the same condition; i. e., as a Solid or liquid and not in end may be accomplished by salting out, etc. aqueous Solution. The N-monochloro primary N-mono-substituted sulfenamides have been amine which is retained in solution decreases the prepared by treating a mixture of a mercaptain yield of the sulfenamide. The yield is independent and a primary amine With an oxidizing agent. 20 of the mercaptide employed. Temperatures below room temperature have been The reaction by which the N-monochloro pri recommended for carrying out such a reaction mary amine is obtained is reversible. It may be (Carr U. S. 2,271,834). It has been proposed to represented by the following equation: produce unsubstituted sulfenamides by reacting a mercaptain With monochloroamine at 0 to 5 C. 25 (Hanslick U. S. 2,261,024 and 2,271,834), British Using an alkali metal or alkaline earth metal 377,730 says that sulfenamides can be produced hypochlorite as the source of chlorine, the hy by the reaction of N-halogen compounds of pri drogen ion concentration is low, and the N-mono mary or secondary amines with mercaptains but chloro primary amine is relatively insoluble. Salt describes only the reaction with secondary amines. 30 ing out decreases the solubility but is expensive It is known that the N-chloro derivatives of pri On a commercial scale. Commercially, the reac Inary annines are much more unstable than those tion is forced to the right by the use of low tem of the secondary amines and British 377,730 does perature and high concentrations, and the amount not attempt to explain how a satisfactory yield of the N-monochloro primary amine in solution can be obtained With an N-chloro derivative of a is thus kept at a minimum. primary amine. Although sodium hypochlorite will ordinarily be The most satisfactory method of obtaining an used, other alkali metal and alkaline earth metal N-mono-chloro primary amine is to react the pri hypochlorites may be employed. Likewise, a mary amine with the hypochlorite of an alkali hypobromite or hypoiodite might be employed metal or alkaline earth metal. Commercially the 40 although generally this is not commercially Sodium salt will ordinarily be used. The N-mono feasible. chloro primary amines are so unstable that ap The concentrations employed will depend on preciable loss occurs if the use of the product the Solubility of the reactants and the tempera is delayed by any process of separation from the ture used. In general, a 1.5 to 3.5 molar con aqueous reaction medium. It has now been found 45 centration of the mercaptide and a 1.5 to 3 molar that a satisfactory yield of N-mono-substituted concentration of the hypochlorite will be found Sulfenamide can be obtained by reacting an aque Satisfactory although higher concentrations may OuS SuSpension of N-monochloro primary amine be used. On mixing the two solutions, the re SO prepared with a mercaptide, provided the Sultant solution will be at least .75 molar with re proper reaction conditions are maintained. Spect to each of the reactants or reaction prod 2,495,085 3 4. ucts. Under proper conditions the mercaptide 10 per cent solution). N-monochloroisopropyl may be used in the undissolved state, or solutions amine separated as a clear oil. To this mixture of the mercaptide and N-monochloro primary Were immediately added i89 grams of Sodium 2 amine in an organic solvent may be used. For mercaptobenzothiazole (333 milliliters of solution instance, an ether extract of the N-monochloro having a concentration of 3 moles per liter). The primary amine obtained from the aqueous reac solid which separated was removed by filtration, tion mixture may be reacted with the mercaptide, Washed and dried. The yield was 219 grams Such as an aqueous solution of the mercaptide, in (98 per cent). The material melted at 89-93° C. which case the reaction appears to take place at iable I shows the effect of the temperature the interface. However, for commercial opera used by Comparing the yields obtained at three tions such solvents are preferably avoided, and different temperatures under comparable condi high molar-solutions will give satisfactory, yields tions. provided a low temperature and high concentra TABLE I tion are maintained. Although equimolecular proportions of the re 5. Effect of temperature on the yield of N-isopro actants enter into the reaction, a slight excess. pylbenaothiaayl Sulfenamide of the primary amine-e.g., 10 to 20 per cent is used to prevent the formation of N-dichloro amine. Targer excess of a volatile amine may be Gram Moles of Reactants used, and the excess subsequently recovered by 20 Wolatilization. However, this increases the cost Reactants for For of the operation and is to be avoided. nation of N Temp., chloroanine Sodium o C. Per Cent, The primary amines which may be used in car 2-mercap Yield tobenzo rying out the reaction include, for example, cyclo Sodium thiazole hexylamine, benzylamine, piperidine, ethylamine, Hypo Isopropyl n-amylamine, methylamine, n-butylamine, n-pro chlorite. Amine pylamine, isopropylamine, allylamine, ethylenedi amine, hexahydrobenzylamine, etc. Alkali metal and alkaline earth metal mer captides which may be used in the process include, for example, those produced from the following mercaptains: thiophenol, thio-beta-naphthol, 2 In Table II different runs are recorded in Which mercaptothiazoline, 2-mercapto 4,5-dihydrogly the same general procedure as Example i was oxaline, 2-mercaptobenzoxazole, 2-mercapto 4,5- employed. They show that by increasing the dimethylthiazole, 2-mercapto-4-ethylthiazole, 2 3 concentration of the reactants, the yield is in mercaptobenzothiazole, 2-mercaptomethylbenzo creased. Part II of Table II shows that high thiazole, 2-mercaptochlorobenzothiazole, and yields may be obtained at low temperatures using. N,N-diethyldithiocarbamic acid. high concentrations even though no great.excess The following data, illustrate the effect of low of amine is employed. ABLE II Effect of the concentration of reactants on the yield of N-isopropylbenaothiaayil sulfenamide. Reactants for,Formation of N-monochloroamine sodium 2-mer. captobenzothi- Reaction . Sodium hypo- azole Mixture Temp., Per Cent chlorite Isopropyl. Molar.Conc o C. Yield Molar SEOS Molar -v-v. Moles E w Moles E Part I.--------------------------- 1.5 1.3 2.0 1.0 3.0 0.70 -10 90 1.5 1.8 2.0 ... 0 3.0 0.85 -0 98 Part II-------------------------- i. () ... 8 1.2 1.0 - 3.0 1.1 -10 74. 3.0 2.5 1:2 . 0 3, 0 1.3 -10 89. ering the temperature and increasing the concen- EXAMPLE 2 tration. Table I shows the effect of lowering the N-cycloheacyl-N,N-diethylthiocarbamyl. temperature. The amount of amine employed is 60 Sulfenamide somewhat in excess of that which will usually be To 0.35 gram mole of cyclohexylamine was employed commercially. The excess may be re added slowly and with stirring 0.32 gram mole of covered by volatilization. It is not necessary to Sodium hypochlorite (177 milliliters of solution. use such a large excess to prevent formation of having a concentration of 1.8 moles per liter) at the N-dichloroamine. The three reactions were a temperature of 5-10° C. N-monochlorocyclo carried out by the general procedure given in hexylamine Separated as a white crystalline. Solid Example 1 which gives the exact conditions en Suspended in the aqueous solution. A portion ployed in carrying out the last of the runs col was filtered, Washed thoroughly with ice water, lected in Table I in which a 98 per cent yield was and dried On... a porous plate at 5-10° C. This was obtained. 70 analyzed for available chlorine. EXAMPLE 1. Calcd. for C6H12NCI, Cli, 26.53 per cent.