CA1060037A - Method of preparing mercaptans - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Merraptans are prepared by reacting an organic chloride or bromide with a mixture of H2S and ammonia or an amine at a temperature of 0 to 175°C. under autogenous pressure. The reaction can be carried out in the presence of a polar solvent. For example, 3-chloroprop???rimethoxy-silane is mixed with H2S and ammonia in methanol and heated in a closed container at 100°C. for 18 hours.

Description

1060()37 One of tlle problems encountered during the preparation Or merca~tans by most Or the common commercial methods is the formation ol by-produced sulfides. This occurs both when H2S is added to unsaturated compounds and ~Ihen the hertofore employed alkali metal hydrosulfides are reacted with chlorides or bromides. The reason for the formation Or sulfi~es in the first process is because the mercaptan adds to a double bond more rapidly than the H2S. With respect to the hydrosulfide reaction, all alkali metal hydrosulfides contain alkali metal sulfides. These give rise to the organic sulfide by-product. Another method which has been employed for the production of mercaptans is shown in U.S. Patent No. 3,590,065. This involves the reaction of an organic halide with thiourea in the presence of ammonia. The products are the mercaptan and guanidine hydrochloride which is voluminous in character and imposes a serious disposal problem.
It is known from U.S. Patent No. 3,849,471 that mercaptoalkyl silicon compounds can be prepared by reacting chloroalkyl-substituted silicon compounds with H2S in the presence of ethylene diamine. This patent shows column 9, Example 13, runs 22 to 25 that amines such as tributyl amine, pyridine and diethylene triamine do not cause the reaction to go to any significant extent. It is, therefore, most unexpected that ammonia and the amines of this inventlon cause the reaction to proceed in excellent yields.
It is an ob~ect of this invention to provide a novel method for preparing mercaptans which5 under the right conditions, avoids the formation of any significant amount of sulfide and which at the same time uses inexpensive reagents.

. '' 1060(~37 Thus, this invention represents an advance in the art of preparing mercaptans which gives economic advantages over prior processes.
This invention relates to a method of producing mercaptans ~Jhich comprises reacting (A) a halide of the formula RXa wlth a mixture of (B) ammonia or a hydrocarbyl amine containing one ~J atom, no more than 6 carbon atoms and being free of aliphatic unsaturation and having a Ka of less than 1 x 10 9 in aqueous solution, and H2S, in the mole ratio of at least one mole of H2S and one mole of (B) per mole of halogen in (A) at a temperature of from 0 to 175C. under autogenous pressure whereby a compound of the formula R(SH)a is formed, in which process R is selected from the group consisting of aliphatic, cycloaliphatic or aralkyl hydrocarbon radicals free of aliphatic unsaturation, such hydrocarbon radicals substituted with alkoxy, keto, carboxyl, hydroxyl, -CooR3 or -ooCR3 in which R3 is a monovalent hydrocarbon radical free of aliphatic unsaturation, and silylated hydrocarbon radicals of the formula (R~tO)yR~ ySiR4~ or 0 dR " 'dSiR4- in which R " is an alkyl or an alkoxyalkyl radical of 1 to 6 carbon atoms, R " ' i5 a monovalent hydrocarbon radical free of aliphatic unsaturation, a haloaryl radical or RfCH2CH2- in which R~ is a perfluoroalkyl radical, R4 is a divalent or trivalent aliphatic, cycloaliphatic or aralkyl radical free of aliphatic unsaturation, y is l to 3, .
and d is 0 to 2, X is bromine or chlorine, and a is 1 to 3.
. It can be seen that the halide reactant (A) can contain 1, 2 or 3 halogen atoms and that these can be chlorine or bromine or a combination thereof. The halogen atom is attached to an allphatic or cycloaliphatic carbon atom and R

--2-- .

.~,,j .

~)6S)037 is free of aliphatic unsaturation. R then, can be any alkyl radical such as methyl, ethylj propyl, isopropyl, hexyl or octadecyl, or any cycloaliphatic hydrocarbon radical such as cyclopentyl, cyclobutyl, cyclohexyl or methylcyclohexyl~ or any aralkyl hydrocarbon radical such as benzyl, beta-phenylethyl,

2-phenylpropyl, beta-xenylethyl, gamma-naphthylpropyl and the like. Typical halides then are ethylc~loride, 1,3-propylene- r dibromide-1,2,3-trichloropropane and 1-chloro-3-bromocyclo-hexane.
In addition, the reactant (A) can be substituted with one or more of the defined substituents so that (A) can be a haloether such as chloromethylmethylether, chloroethyl-ethylether, bis-chloromethylether, chlorobutylmethylether, chloromethylphenylether or chloromethylbenzylether; or halo~enated ketones such as bromomethylmethyl ketone, chloro~ethylethyl ketone, chloromethylphenyl ketone, chloroethylbenzyl ketone or bis-chloroethyl ketone;
halogenated carboxylic acids such as chloroacetic acid, -~
alpha-chloropropionic acid, beta-bromopropionic acid, gamma-chlorobutyric acid or chlorocyclohexylcarboxylic acid.
It should be understood, of course, that the products formed by the reaction of a halogenated acid produces the corresponding ammonium or amine salt~ The free acid can be obtained by reacting this salt with a strong acid such as hydrochloric, nitric, etc. In addition, (A) can be a halo alcohol such as beta-chloroethanol, beta-chloropropanol or bromohexanol. (A) can be an ester of a halogenated ~-carboxylic acid which ester contains the group -COOR3 in which R3 iS a mono~alent hydrocarbon radical such as methyl, ethyl, isopropyl, butyl, phenyl, cyclohexyl or , .
- .
.

10~60037 benzyl or (A) can be a carboxylic acid ester of a halo alcohol which ester contains the group -ooCR3 in which R3 is as above described.
In addition, (A) can be a silane of the formula (Rl'O)yR'l' ySiR4~ or a siloxane of the formula 03-dR " 'dSiR4-in which silanes and siloxanes R'' is any alk~l radical suchas methyl, ethyl, isopropyl, butyl or hexyl or any alkoxyalkyl radicals such as -OCH2CH20CH3 or O(CH2CH20)2C2H5 and R " ' is any monovalent hydrocarbon radical free of aliphatic unsaturation such as methyl, ethyl, isopropyl, butyl, phenyl~
xenyl, naphthyl, benzyl, beta-phenylethyl, 2~phenylpropyl or cyclohexyl; any haloaryl radical such as chlorophenyl, dichlorophenyl, chloroxenyl or chloroanthracyl or ~luorinated hydrocarbon radicals of the formula RfCHzCH2-in which Rf is any perfluoroalkyl radical such as perfluoromethyl, perfluoroethyl, perfluorobutyl, perfluoro-isobutyl or perfluorooctyl. The divalent radical R4 between the halogen and the silicon can be any divalent aliphatic hydrocarbon radical such as methylene3 dimethylene, trimethylene, isobutylene or ocatdecamethylene or any cyclo-alkyiene radical such as cyclohexylene, methylcyclohexylene, cyclopentylene or cyclobutylene or any araIkylene radical ln whlch the silicon is attached to the aromatic ring, such Me as benzyleneg -C6H~CH2CHz-~ -C~H4CHCH2-, o~ -CH2CH2C6H4CH2-.
R~ can also be trivalent or tetravalent radicals of the ~bove type ln which case a has a value of 2 or 3 respectively.
The slloxanes employed as reactants can be homopolymers or copolymers and they can have either 1, 2 or

3 organic radicals substituted on the silicon atom. Also _4_ ~060~3'7 these slloxanes can contaln ;ome sllicon-bonded hydroxyl groups and some copolymerized organosiloxane un~ts, which are free of reactive halogenated units of the formula R'~'zSiO4-z in which R " ' is aS above defined and z i9 0 to 3, such as, for example, dimethylsiloxane units, phenylmethyl-- siloxane units, trimethylsiloxane units, trifluoropropyl-methylsiloxane units, diphenylsiloxane units, monophenyl-siloxane units, monomethylsiloxane units or sio2 units. Of course, in these copolymers there should be at least one siloxane unit having the defined ~R9~a substituents. SucA
copolymers are considered within the process Or this invention.
Reactant (B) employed in this invention can be ammonia or any hydrocarbon amine containing one ~ atom and no more than 6 carbon atoms which is free of aliphatic unsaturation and has a Ka of less than 1 x 10 9. This means that the amines are those in which the nitrogen is attached to aliphatic or cycloaliphatic carbon atoms, Specific examples of such amines are primary amines such as methyl amine, butyl amine, isopropyl amine, cyclohexyl amine and cyclopentyl amine;
secondary amines such as dimethyl amine, dipropyl amine and methylbutyl amine and tertiary amines such as trimethyl amine, triethyl amine or ethyldimethyl amine. The total number of carbcn atoms in the amine should be no more than 6.
The mole ratio of (B) to H2S is not critical since either can be in large excess over the other. However, for best results there ~hould be at least one mole of H2S and one mole of (B) per mole of halogen in (A).
The reaction of this invention is best carried out at a temperature from 0 to 175C. under autogenous pressure.
The optimum temperature to be employed with any particular type of reagent varies, but in general~ the higher the _ ~-r ~ r~

~16~037 temperature, the less sulfide produced. The pressure, of course, will vary with the temperature and the volati;ity of the reactants. If desired, external pressure can be applied to the system, but this is unnecessary because the autogenous pressure is sufficient for excellent yields.
In many cases, it is advantageous to employ a polar solvent in the reaction. ~xamples of operative polar solvents are water, alcohols such as methanol, ethanol, isopropanol or butanol; ethers such as dioxane, the dimethyl ether of ethylene glycol or the monomethyl ether of ethylene glycol;
nitriles such as acetonitrile or propionitrile;
N,N-disubstituted amides such as dimethyl acetamide or diethyl formamide and sulfur compounds such as dimethyl sulfoxide. Obviously, the polar solvent should be non-acidic.
The following examples are illustrative only and should not be construed as limiting the invention which is properly delineated ln the appended claims. In the examples, the following abbreviations are used: Me for methyl, Et for ethyl, Pr for propyl and Ph for phenyl.
Example_l Trimethyl amine (37 g., o.637 moles), hydrogen sulfide (14.1 g., 0.415 moles) and (MeO)3Si(CH2)3Cl (72 g., o.36 moles) were heated at 100C. in a 300 ml. stainless steel autoclave. After 17 hours, a sample was withdrawn and analyzed by ~lc. Chloropropyltrlmethoxysilane was not detected by glc. The ma~or product was (MeO)3Si(CH2)3SH
(97 percent glc area) with small amounts of [(MeO)3Si(CHz)3]2S2 and [(MeO)~Si(CHz)3]2S.

.

~0~;0037 Exa~ple 2 A solution o~ equal ~olumes of triethyl amine and methanol were saturated wlth hydrogen sulfide at room temperature and atmospheric pressure. The H2S was present in excess of 1 mole H2S per mole of amine. 3.49 g. of n-hexyl chloride was added to 15 ml. of the above solution and the mixture was heated in a sealed container at 75C.
After 6 hours, the product was 99.1 percent n-hexyl mercaptan and 0.9 percent n-hexyl sulfide.
Example 3 78.4 g. of ammonia and 171 g. of hydrogen sulfide were added to a three liter stainless steel autoclave. 100 ml.
of methanol were pumped into the vessel followed by 819 g. of n-dodecyl chloride. This was followed by 20 ml. of methanol to flush out the pump. The sealed container was heated at 125C. and after 22 hours gas liquid chromotography analysis showed that the product was 98.7 percent n-dodecyl mercaptan and 0.~ percent unreacted dodecyl chloride.
Example 4 3.3 g. of am~onia was added to 31.7 ml. of methanol and then the solution was saturated with hydrogen sulfide.
While continuing the hydrogen sulfide addition, 19 ml. of benzyl chloride was added and the mixture maintained at 0C.
After one hour, gas liquid chromotography indicated that the product was 92 percent benzyl mercaptan and 8 percent benzyl sulfide~
Example 5 A mixture of a saturated hydrogen sulfide solution of 12.6 g. of benzyl chloride, 8.4~g. of n butyl amine, and 20 ml. of isopropanol was reacted at room temperature. After .

.. , . , . ' . ~ ' ~(~6003~7 15 to 30 n-inute~, ~as liquid chromotography analysis showed that tlle reaction was 90 p~rcent complete ~nd the distribution of materials was 10 percent unreacted benzyl chloride, 82 percent benzyl mercaptan and 6 percent ben~yl sulfide.
Example 6 A solution of 10.9 g. of 1,2-dibromoethane, 13.5 g. of dipropyl amine and 10 ml. of methanol was saturated with H2S and reacted at room temperature. Analysis of the product by gas liquid chromotography showed it to be 1,2-ethane dithiol. No by-products were found.
Example 7 98 g. of ammonia, 211 g. of hydrogen sulfide and 990 g. of 3-chloropropyltrimethoxysilane were heated at 100C. in a closed container. After 5.7 hours, the reaction was 81 percent complete and the product was 3-mercaptopropyl-trlmethoxysilane.Example 8 A mixture of 95.9 g. of ammonia, 192.2 g. of hydrogen sulfide, 970 g. of 3-chloropropyltrimethoxysilane and 150 ml. of methanol were heated in a closed container at 100C. for 18.5 hours. The initial pressure was 195 p.s.i.g.
(15.7 kg/cm2). After 18.5 hours, the pressure was 85 p.s.i.g.
(5.95 kg/cm2). The mixture was cooled and filtered free of ammonium chloride. The ammonium chloride was washed twice with 200 ml. portions of hexane. The original filtrate and the hexane were combined and distilled. The product was shown by gas liquid chromotography analysis to be 96.2 percent 3-mercaptopropyltrimethoxysilane, 3.2 percent unreacted chloropropyltrimethoxysilane and 0.5 percent of an unidentified impurity originally present in the chloropropyl trlmethoxysilane. In other words, no sulfide was detected.

1~60037 Example 9 In an evacuated autoclave was charged 99 g. of ammonia and 198 g. of hydrogen sulfide and the autoclave was heated to 100C. 924 g. of 3-chloropropylmethyldimethoxy silane and 100 ml. of methanol were then pumped into the autoclave and heating was continued for 26.75 hours. After cooling, the autoclave was emptied and the contents filtered free of ammonium chlor~de. Gas liquid chromotography analysis Or the product indicated a yield of 97 percent with a 94.2 percent conversion of the chloride to the mercaptan.
Example 10 682.5 g. of a siloxane of the unit formula Cl(CH2)3SiMeO containing 1.41 percent by weight silicon-bonded hydroxyl groups, 100 ml. of methanol, 97.5 g. of ammonia and 195.5 g. of hydrogen sulfide were mixed and heated at 125C.
for 24 hours. The initial pressure in the autoc}ave at 125~C. was about 500 p.s.i.g. (35.15 kg/cm2). After 24 hours, the pressure was 195 p.s.i.g. (13.6 kg/cm2)r After 24 hours at 125C., the product was cooled and diluted with ether and filtered free of ammonium chloride. The product was devolatilized at 2 mm. pressure at 60C. for 4 hours~ The resulting product was 3-mercaptopropylmethylpolysiloxane having the following properties: n25 1.5038, d-~ 1.115, Rd 0.2655, Cal. Rd 0.2666. The yield of product was 95 percent.
Example 11 Equivalent results are obtained when cyclohexyl amine is substituted for the triethyl amine of Example 2.

.

_ g _ .
,., .~ .-, Example 12 Merca~tans are obtained when the following halides are reacted with a mixture of ammonia and H2S ln the mole ratio of 1:1 at 100C. under autogenous pressure.
Example 13 The experiment of Example 9 was repeated with NH3 (100 g., 5.88 m~), H2S (127.5 g., 3.75 m.) and methanol (100 ml.) at 100C. (MeO)2MeSi(CH2)3Cl ~593 g., 3.25 m.) ~Jas pumped into the autoclave followed by 100 ml. of methanol.
Periodic analyses indicated:

Time %Initial Hours(MeO)2MeSi(CH2)3Cl (MeO)2MeSi(CH2)3SH

0.5 13.1 85 1.5 5.8 92.1 2.5 2.6 94-7 This reaction was much faster than that of' Example 9.

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Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of producing mercaptans which comprises reacting (A) a halide of the formula RXa with a mixture of (B) ammonia or a hydrocarbyl amine containing one N atom, no more than 6 carbon atoms and being free of aliphatic unsaturation and having a Ka of less than 1 x 10-9 in aqueous solution, and H2S, in the mole ratio of at least one mole of H2S and one mole of (B) per mole of halogen in (A), at a temperature of from 0 to 175°C. under autogenous pressure whereby a compound of the formula R(SH)a is formed, in which process R is selected from the group consisting of aliphatic, cycloaliphatic or aralkyl hydrocarbon radicals free of aliphatic unsaturation, such hydrocarbon radicals substituted with alkoxy, keto, carboxy, hydroxyl, -COOR3 or -OOCR3 radicals in which R3 is a monovalent hydrocarbon radical free of aliphatic unsaturation, and silylated hydrocarbon radicals of the formula (R''O)yR'''3-ySiR4- or in which R'' is an alkyl or an alkoxyalkyl radical of 1 to 6 carbon atoms, R''' is a monovalent hydrocarbon radical free of aliphatic unsaturation, a haloaryl radical or RfCH2CH2- in which Rf is a perfluoroalkyl radical, R4 is a divalent or trivalent, aliphatic, cycloaliphatic or aralkyl hydrocarbon radical free of aliphatic unsaturation, y is 1 to 3, and d is 0 to 2, X is bromine or chlorine, and a is 1 to 3.

2. The process of claim 1 which is carried out in a non-acidic, polar solvent.