3,086,049 United States Patent Office Patented Apr. 16, 1963 1. 2 6-Cyclohexylethylthioacetate 3,086,049 ?y-Cyclohexylpropylthioacetate MERCAPTAN AND AMDE PRODUCTION 8-Cyclohexybutylthioacetate John J. Godfrey, Silver Spring, Md., assignor to Cali n-Dodecylthiopropionate fornia Researci Corporation, San Francisco, Calif., a Undecylthiopropionate corporation of Delaware Decylthiopropionate No Drawing. Fied Mar. 16, 1960, Ser. No. 15,262 Nonylthiopropionate 2 Clains. (C. 260-561) Octylthiopropionate This invention relates to the preparation of mercaptans Isobutylthiopropionate and from thioesters. O 6-Phenylethylthiopropionate The mercaptains and amides obtainable pursuant to the ?y-Phenylpropylthiopropionate process of the present invention are known to have utility 8-Phenylbutylthiopropionate in various fields. For example, the mercaptains are known B-Cyclohexylethylthiopropionate to have utility in the field of rubber manufacture, and ty-Cyclohexylpropylthiopropionate certain of the amides are known to have direct utility, for 5 8-Cyclohexylbutylthiopropionate example as solvents, as well as utility in organic syn n-Dodecylthiobutyrate thesis. Undecylthiobutyrate The thioesters from which mercaptains are prepared Decylthiobutyrate pursuant to the process of the present invention may be Nonylthiobutyrate prepared in various conventional ways, for example by the 20 Octylthiobutyrate free radical addition of thioacids to olefins. isobutylthiobutyrate It is known that mercaptains can be prepared from thio g-Phenylethylthiobutyrate both by hydrolysis and alcoholysis. However, proc ?y-Phenylpropylthiobutyrate esses involving either of these routes have serious disad 8-Phenylbutylthiopropionate vantages; for example the hydrolysis of these water-in 25 6-Cyclohexylethylthiobutyrate soluble esters is extremely slow, and alcoholysis results ty-Cyclohexylpropylthiobutyrate in only fair yields. 8-Cyclohexylbutylthiobutyrate it has now been found that thioesters can be converted Thioesters of less than 4 carbon atoms are not con to mercaptains and amides quickly and in good yields by prehended by the process of the present invention; as a reaction with certain nitrogen-containing compounds. Re 30 practical matter the advantages and utility of the process actions are efficient and complete at low temperatures are offset by limitations as to availability of feed to the and pressures, although moderately higher temperatures process. For example, thioacetic acid is readily obtained and pressures also are operable. The nitrogen-containing in a variety of ways, for example by the reaction of ketene compounds include , whereby ammonolysis is with hydrogen sulfide or by a base catalyzed reaction of effected, and certain , whereby aminolysis is 35 hydrogen sulfide with acetic anhydride. The thioacid in effected. For example: turn is readily converted to a thiol by a free radical Aminolysis addition to an olefin; however, because ethylene and O O thioacetic acid are the lowest molecular weight Species 40 for the respective homologous series, C4 is the carbon ROHOHscH, -- R'NH2 - RCH2CH2SH -- CH&NHR lower limit. Thioesters having more than 20 carbon Ammonolysis atoms are not comprehended by the process of the present O O invention, because as a practical matter distillation cuts RCHCHsé CH, -- NH3 - RCH2CH2SH -- CH&NH, made in preparing feed stocks commonly are made at a 45 Co cut point, and because the reaction with higher molec The thioesters suitable in the process of the present ular weight thioesters is impracticably slow. invention are aliphatic thioesters having The amines suitable in the process of the present in 6 to 20 carbon atoms, preferably 6 to 14 carbon atoms, vention are primary and secondary aliphatic amines hav and having the general form ing less than six carbon atoms and having the general 50 form: RSCR RNHR where the RCO, or acid, portion of the molecule is where RandR' may be the same or different groups, derived from an aliphatic carboxylic acid, viz., acetic, or one may be hydrogen and the other an alkyl group. propionic or butyric acid, thus making R' contain one, 55 Examples of the above suitable amines include: two or three carbon atoms, respectively, and where R Methylamine in the RS, or mercaptan, portion of the molecule is an Ethyl organic radical containing a chain of at least 2 aliphatic n-Propyl amine carbon atoms linked to the sulfur of the thioacid, and Isopropyl amine which may contain one or more substituents that are inert 60 Butyl amine under the conditions of the reaction, including, for ex Methyl ethylamine ample, aryl-, alkyl-, alkoxy- and cycloalkyl-substituents. Methyl isopropylamine Examples of the above suitable thioesters include: Dimethyl amine n-Dodecylthioacetate Diethylamine Undecylthioacetate Decythioacetate Aromatic and tertiary amines are unsatisfactory in the Nonylthioacetate process of the present invention. As the molecular Weight Octylthioacetate of the amine increases, the reaction slows down to the ex Isobutylthioacetate tent that amines having six or more carbon atoms are un g-Phenylethylthioacetate 70 satisfactory. ?y-Phenylpropylthioacetate The process of the present invention may be conducted 8-Phenylbutylthioacetate with the thioester in liquid phase, or in vapor phase. 3,086,049 3 4. However, from a practical standpoint liquid phase is pref During the period of addition, the temperature rose from erable because of the difficulties attendant upon achieving 20° C. to 60° C. Upon completion of the reaction the re vapor phase operation and because of the increased equip action mixture was cooled to room temperature, at which ment size involved in such operation. temperature it consisted of two separate organic liquid The process generally is conducted at from about the phases, one substantially comprising N,N-dimethyl acet melting point of the thioester feed to about its boiling and one substantially comprising n-dodecyl mer point. The upper, or boiling point temperature limitation captain. The mercaptain and amide were recovered in is meaningful for the lower thioesters, for example those high yield by separation of the phases and water washing having up to about 12 carbon atoms, but becomes less of the mercaptain phase to remove traces of the amide. meaningful with higher molecular weight thioesters, the O boiling points of which rise rapidly with increasing molec Example 5 ular weight. The reaction is exothermic, and at higher Using the same procedure as in Examples 3 and 4, temperatures during continuous operation it may be found Co-Cao thioacetate was reacted with anhydrous methyl desirable to add the amine or ammonia more slowly. At amine. Rapid addition of the amine to the thioacetate hgiher temperatures undesirable side reactions tend to 5 caused an exotherm after which the temperature of the occur, including air oxidation where the reaction is not reaction flask was maintained at 80° C. for a period of conducted in an inert atmosphere. In view of the fore two hours. Upon cooling, phase separation occurred at going, a practical temperature range for conducting the 60-65 C. The separated mercaptain phase was freed reaction is from about 0° C. to 200° C., and preferably from the N-methylacetamide phase by water washing, from about 15 C. to 150 C. and the mercaptain and amide were recovered in high The process may be conducted with or without a sol yields. vent. If a solvent is used, it may be an inert solvent such Example 6 as pentane or hexane, with which temperature can be Equimolar amounts of aniline and n-dodecylthioacetate controlled by the attachment of a reflux condenser to the were heated at 80° C. for two hours. No reaction oc reactor; in this way heat of reaction can be removed. curred, thus indicating the inoperability of the aromatic The process may be conducted in either a batchwise amine in the present process. or continuous manner, subject to the need for adequate From the foregoing it may be seen that the process of temperature control with the various possible reactants, the present invention provides a highly effective route to because of the exothermicity of the reaction. two useful products from a thioester starting compound, The following examples will serve to further illustrate 30 and that the process is a distinct improvement over al the process of the present invention. coholysis and hydrolysis processes for producing mercap Example 1 tans from thioesters, particularly in that the reaction pro ceeds more quickly, yields are better, and an amide prod n-Dodecyl thioacetate was placed in a bomb connected luct is produced in addition to a mercaptan. to a tank of ammonia and was allowed to react with the No limitations are intended in connection with the ammonia in liquid phase at room temperature. The re process other than those appearing in the appended claims. action proceeded to completion, with controlled evolution I claim: of heat, in a few minutes. The reaction mixture was re 1. A process for producing a mercaptain and an amide moved from the bomb and was found to separate into from a water-insoluble thioester having from 6 to 20 two layers, one layer substantially comprising n-dodecyl 40 carbon atoms and having the formula: mercaptan, and the other layer substantially comprising O acetamide, a polar compound immiscible with the long RCHCHS-E-R chain alkyl mercaptan. The two layers were separated where R is an alkyl selected from the group consisting from each other with ease by water washing, because the of methyl, ethyl and propyl and where R is a member of acetamide is water-soluble and may be readily washed 45 the group consisting of alkyl of at least 2 carbon atoms, from the n-dodecyl mercaptain with water. carbocyclic aryl and cycloalkyl, which consists essentially Example 2 in forming a mixture consisting of said thioester and am n-Dodecyl thioacetate was reacted with sufficient methyl monia as the sole reactants, maintaining said reaction amine, added over a period of one hour, to completely mixture in a reaction zone at a temperature between about react with the thioester. During the period of the addition 50 0 to about 200 C., thereby forming a mercaptain phase the temperature rose from 20° C. to 60° C. Upon com and an amide phase, and recovering the mercaptain and pletion of the reaction the reaction mixture was cooled to the amide so obtained. room temperature, at which temperature it consisted of 2. A process for producing a mercaptain and an amide two Separate organic liquid phases, one substantially com from a water-insoluble thioester having from 6 to 20 prising N-methyl acetamide and one substantially com carbon atoms and having the formula: prising n-dodecyl mercaptan. The mercaptain and amide O were recovered in high yield by separation of the phases RCH-CHS-C-R and water washing of the mercaptain phase to remove where R is an alkyl selected from the group consisting traces of the amide. Negligible side reactions occur in of methyl, ethyl and propyl and where R is a member this low-temperature region, and yields with the various 60 of the group consisting of alkyl of at least 2 carbon atoms, thioester starting materials are essentially quantitative phenyl and cycloalkyl, which consists essentially of form without recycle or can be made so by recycle of any un ing a mixture consisting of said thioester in liquid phase converted ester. and amonnia as the sole reactants, maintaining said Example 3 mixture in a reaction Zone at a temperature between The procedure in Example 2 was repeated, with the only about 15 to about 150° C., thereby forming a mercaptain changes being the use of n-butylamine instead of methyl phase and an amide phase, and recovering the mercaptain amine, and the maintenance of the temperature at 80° C. and the amide so obtained. for 30 minutes by application of heat. The products were References Cited in the file of this patent n-dodecyl mercaptain and N-n-butyl acetamide. 70 UNITED STATES PATENTS Example 4 2,238,928 Cohn et al. ------Apr. 22, 1941 n-Dodecyl thioacetate was reacted in a stirred 500 ml, 2,709,164 Wieland ------May 24, 1955 3-neck flask with sufficient dimethyl amine, added over a 2,786,048 Schwyzer ------Mar. 19, 1957 period of one hour, to completely react with the thioester. 75 (Other references on following page)

3,088,049 5 6 OTHER REFERENCES published by John Wiley and Sons, Inc. (New York), pages 213-214 (1945). Conant: The Chemistry of Organic Compounds, pub Degering: An Outline of Organic Nitrogen Compounds, lished by The Macmillan Company (New York), pages published by University Lithoprinters (Ypsilanti, Mich.), 264-265 (1939). pages 397-399 (1950). Hackh's Chemical Dictionary: (3rd Ed.), published by Reid: Organic Chemistry of Bivalent Sulfur, Volume 1, the Blakiston Company (Philadelphia), page 30 (1944). page 29, published by Chemical Publishing Co., Inc. (New Lowy et al.: An Introduction to Organic Chemistry, York), 1958.