Process for Preparing mono- and di-alkylmercaptophosphorothionochloridates
[ Apr. 22, 1975 PROCESS FoR PREPARING MONO- AND DI-ALKYLMERCAPTOPHOSPHOROTH- IONOCHLORIDATES [75] Inventors: Eugene H. Uhing, Ridgewood. N.J.;  
 Arthur D. F. Toy, Stamford. Conn.  
 [73] Assignee: Stauifer Chemical Company,  
 Westport, Conn.  
 [22] Filed: Oct. 15, 1973 [2]] Appl. No.: 406,746  
 [52] US. Cl. 260/981; 260/960; 260/986 [5 1] Int. Cl. C07f 9/20 [58] Field of Search 260/981. 986  
 [56] References Cited UNITED STATES PATENTS 2.405.482 8/1946 Zimmcr ct al. 260/981 X 2,836,534 5/1958 Birum 260/98l X Primary Examiner-Lorraine A. Weinberger Assistant E.\&#39;aminerRichard L. Raymond [57] ABSTRACT This invention provides a process for the preparation of monoand di-alkylmercapto phosphorothionochloridates. In this reaction an alkyl chloride and phosphorus pentasulfide are reacted at an effective temperature in the range of from about 160 to about 300 C. depending upon the particular alkyl halide employed. As an embodiment of this invention a method is set forth for the production of monoalkylmercapto phosphorothionodichloridate.  
 28 Claims, No Drawings PROCESS FOR PREPARING MONO- AND DI-ALKYLMERCAPTOPHOSPHOROTHIONO- CHLORIDATES This invention relates to a process for the manufacture of monoand di-alkylmercapto phosphorothionochloridates.  
  The alkylmercapto phosphorothionochloridates find particular utility as intermediates for compounds which exhibit biocidal properties, particularly insecticidal and herbicidal properties.  
  In the past, a number of processes have been proposed to prepare compounds similar to those prepared by the processes of this invention. For example:  
 (1) P(S)Cl RSH (RS)P(S)C1 (2) RSPCl s Rs-P(s)c12 (3) P(S)Br 2 Hg-C- CH-CH BrP(S (s-cn -cn-cn 2 These prior art processes are described in detail in Methoden Der Organishen Chemie Band XII/ 1, Teil 1 pages 682-683 and 739-740 (1963) published by Georg Thieme Verlug, Stuttgart, Germany. These processes have been found to some extent to be deficient in that the product is limited to the dichloride or the monochloride, the yields are too low or the trialkyl mercapto analog is formed.  
  The present process is believed to provide greater control over product formation and improved yields.  
  In accordance with the present invention, it has been found that the monoand di-alkylmercapto phosphorothionochloridates are prepared by the reaction of a corresponding alkylchloride and phosphorus penta- Sulfide (P4810).  
  This reaction can be represented by the following equation 1:  
 In the equation above, R is lower alkyl, aralkyl or cyclohexyl. By the term lower alkyl it is intended to include both n-alkyl and secondary alkyl. Preferably the lower alkyl group contains from 1-8 carbon atoms inclusive and preferably from 1-4 carbon atoms. Representative of rare methyl, ethyl, n-propyl, isopropyl,-nbutyl, cyclohexyl and benzyl.  
  The reactants employed in the process of this invention can be employed in stoichiometric amounts, although excess of either reactant can be used if desired. It is generally preferred to employ the alkyl chloride in excess.  
  The temperature at which the reactions of this invention are conducted are between about 160 and 300C. depending upon the particular alkyl chloride employed. The specific reaction temperature employed depends to a certain extent on the reactants employed and the time in which the reaction is to be run. However, the reaction temperature is critical and should generally be maintained within the range of 200 to 300C. Certain alkyl chlorides such as isopropyl chloride will react below 200C. The lower range can be easily determined by those skilled in the art. Above about 300C. the reaction products begin to degrade.  
 This limit is also easily determined by those skilled in the art.  
  The reaction of this invention can be run at atmospheric or super-atmospheric pressures. The choice of pressure is determined primarily by the reactants. When high boiling chlorinated alkyls are reacted, atmospheric pressure can be employed. When low boiling materials are used, it is necessary to employ superatmospheric pressure. For ease of reaction control it is preferred to employ autogenous pressure. Autogenous pressures as high as about 3000 psig can occur during the reaction.  
  As can be seen from reaction 1 above, both the rnonoand dichloride product is formed. It is an embodiment of this invention to direct the product almost in its entirety to the dichloride derivative through the incorporation of thiophosphorus trichloride in the reaction mixture in accordance with the reaction Mechanism 2 as set forth below:  
  Alternatively, the conversion to the dichloride can be accomplished after the product has been formed according to reaction (1) by reacting-the monochloride product with PSCl The PSCl can be reacted with the separated monochloride product or can be added to the reaction mixture. The reaction proceeds according to reaction mechanism (3) set forth below:  
 (RS) P(S)Cl PSCl 2RSP(S)C1 EXAMPLE 1 Reaction with Methyl Chloride In a 300 ml. stainless steel autoclave was placed 66 grams of P 5 (molecular weight 444; 0.15 mole). To this was added 45 grams of methyl chloride (molecular weight 50.01; 0.9 mole). The autoclave was heated at 200C. for 4 /2 hours and at 215C. for 2 hours. The pressure dropped sharply after 2% hours of heating. A pour out yield of 109 grams was obtained. Analysis of the reaction mixture by gas liquid chromatography showed the following composition:  
 Component Area PCl; 2.6 PSCl 2.2 Cl-I;,SP(S)Cl 43.1 )P(S)C1 45.1 4.8  
 EXAMPLES 24 Reaction with Methyl Chloride The reaction of Example 1 was repeated varying the temperature and the time of reaction with the results set forth in Table 1 below:  
 TABLE 1 Gas (&#39;hromatograph Assay of Crude Product &#39;7&#39; Example &#39;lcmpfC. Time-(hrs. P(&#39;l PSCL, I II 111 2 190 13 No Significant Reaction Producl (IL,S1(S|(&#39;I., Product 11 HHJSHIISK&#39;I Product lll ((IGSHPS As the reaction temperature increases it will be noted EXAMPLE 8 t t o d b hat he yield f eslred products tend to e lower The 25 Reaction with Ethyl Chlonde decrease in yield is believed to be due to the reaction of methyl chloride with product already formed to form methyl thioether. It is also believed that the products have relatively low thermal stability and form byproducts such as methylphosphonothioic dichloride (CH P(S)Cl and dimethylphosphinothioic chloride [(CH P(S)C1]. In addition to the loss in yield represented by their formation, the byproducts can subsequently enter into exchange reactions with the primary products thereby further decreasing the yield.  
  The 300 ml. stainless steel autoclave was charged with 58 grams of ethyl chloride (0.9 mole) and 67 grams of phosphorus pentasulfide (0.15 mole). Thereaction mixture was heated to a temperature of 200C. and maintained at this temperature for 13 /2 hours. After the reaction period the reaction mixture was cooled and the product of the reaction recovered. The recovered product contained 51 grams of unreacted ethyl chloride and 3 grams of a liquid product. The re- It was also noted during the experiments set forth as sults indicated that the reaction temperature was not Examples 2-7 that at the lowest reaction temperature high enough. of 200C. there was an induction eriod of several hours before any reaction occurred indicated by the EXAMPLE 9 sharp pressure drop which occurs when the gaseous Example 8 was repeated except the reaction was conmethyl chloride reacts with the solid phosphorus pentaducted at a temperature of 230C. for 13% hours. After sulfide. cooling, 8 grams of unreacted ethyl chloride was Purification of the products set forth in Table 1 revented from the autoclave, 110 grams of a black viscover a purified yield of about 90 percent of the prodcous liquid product was recovered. Analysis by gas ucts in the crude mixture. Analysis of the preferred chromatography showed the crude product to contain products (1 and 11) obtained through the reaction of 21 percent of Product 1V and 42 percent of Product V. methyl chloride and phosphorus pentasulfide at a tem- Five byproducts were present in the 5-10 percent perature of 200 to 215C. is shown below. range.  
 Compound Found Calcld. Found CH SP(S)Cl-, 17.05 35.7 39.4 17.1 35.4 39.2 1.6126 ((HHSLZHSKI 15.210 50.4 19.3 16.1 50.0 18.5 1.6470  
 The H-nmr spectra confirms the structures as shown. The crude product was distilled at a temperature of Furthermore. the presence of (CH S) PS was con- 70160C. at 7600.05mm Hg. pressure to yield 63.5 firmed by H-nmr spectra identical to that reported in grams of distilled product. This material was redistilled the literature. Boiling points were determined for the to give 15 grams of Product 1V having a boiling point two products as follows: of 30C. at 0.05 mm Hg. and n of 1.5893.  
 Product 1 CH SP(S)Cl 25-30C. at 0.1 mm Hg Product IV C H SP(S)Cl Product 11 (CH S) P(S)Cl 75-78C. at 0.1 mm Analysis Found: P, 15.5; S, 32.4; C1, 36.9.  
 Hg Calcd: P, 15.9; S, 32.8; CI, 36.4.  
  In Examples 1-7 above the reaction was conducted at autogenous pressure in a 300 ml. stainless steel autoclave rated for 5,000 lbs. per square inch pressure.  
  16 grams of Product V which had a boiling-point of 92C. at 0.01 mm Hg. an n of 1.6096 were also recovered.  
 Product V (C H S) P(S)Cl Analysis Found: P, 14.7; S, 43.4; C1, 17.3. Calcd: P. 14.1; S, 43.7;C1, 16.1.  
 EXAMPLE Reaction with 2-Ch1oropropane 70 grams of 2-chloropropane (0.9 mole) and 66.6 grams of P 5 (0.15 mole) were charged to the 300 ml. stainless steel autoclave of Example 1. The autoclave was heated to a temperature of 200C. for a period of hours. After cooling the vent gas was analyzed and found to contain 0.2 mole HCl. There remained 120 grams of a dark liquid. Gas chromatograph analysis of the dark liquid indicated 10 different products were present. It was concluded that the reaction temperature was too high or the reaction time too long.  
 EXAMPLE 1 1 Example 10 was repeated except that the reaction mixture was maintained at 160C. for 18 hours. The reaction mixture was found to contain 43 grams of unreacted 2-chloropropane. It was concluded that the temperature was too low or the reaction time too short. Example 10 was repeated except that the temperature was maintained at 190C. for a period of 19 hours. Gas chromatograph analysis indicated the reaction mixture contained 6.7 percent unrcacted 2-chloropropane; 13 percent isopropylmercapto phosphorothionodichloridate; 18 percent diisopropylmercapto phosphorothionochloridate and 7 other products present in the 5-20 percent range. 1  
 EXAMPLE 12 Example 10 was repeated except that 70 grams (0.9 mole) of 2-chloropropane was reacted with 66.6 grams (0.15 mole) of P 8 at a temperature of 170C. for a period of 58 hours. After cooling, 79 grams ofa liquidsolid product mixture was obtained from the autoclave. After filtering to remove the solids, the yield of liquid was 62 grams. Gas chromatographic analysis of the liquid showed it contained 20 percent 2chloropropane; 13 percent isopropylmercapto phosphorothionodichloridate; 18 percent di-isopropylmercapto phosphorothionochloridate and 23 percent high boiling point material. The crude product was distilled to yield 8 grams of isopropylmercapto phosphorothionodichloridate which had a boiling point of 34C. at 0.1 mm Hg. and n,,&#34; 1.5682.  
 Analysis for C,-,H S P(S)Cl Found: P, 14.5; S, 30.1; CI, 34.2.  
 Calcd: P, 14.6; S, 30.5; CI, 34.0.  
  1 1 grams of di-isopropylmercapto phosphorothiont chloridate was also recovered from the crude product. This material had a boiling point of 67C. at 0.1 mm Hg. and n,, of 1.5774.  
 Analysis for (C H S) P(S)C1- Found: P, 12.6; S, 38.7;C1, 15.1.  
 Calcd: P. 12.5; S. 38.7; CI, 14.3.  
 EXAMPLE 13 Reaction with l-Chloropropane .70 grams of l-chloropropane (0.9 mole) and 66.6 grams of P 3 (0.15 mole) were charged to the 300 milliliter stainless steel autoclave used in Example 1.  
 The mixture was heated at a temperature of 200C. for a period of 19 hours. No pressure drop was observed. The reaction mixture was then heated to 250C. for a period of 18 hours and a slight pressure increase was observed. The autoclave was vented. 104 grams of a black viscous product remained in the autoclave. The crude product was distilled to give 33 grams of a mixture of compounds.  
 EXAMPLE 14 Reaction with Benzyl Chloride To a 250 ml. 3 neck pyrex flask fitted with a reflux condenser, thermometer and stirrer was charged 57 grams of benzyl chloride (0.45 mole) and 33.3 grams of P S ,(0.075 mole). The reaction mixture was kept under a nitrogen atmosphere and heated to a temperature of 160-175C. with stirring for 3 hours. All solid P 8 had disappeared at this time. The reaction mixture was heated for 2 additional hours at a temperature of 165C. The reaction product was recovered directly. Gas chromatograph analysis showed almost all the henzyl chloride had reacted. The crude product was distilled to yield 27.0 grams of a liquid having a boiling range of 1 15145C. at 0.1 mm Hg. H-nmr analysis indicated that both the monobenzyldichloride product and the dibcnzylmonochloride product were present. 1t was determined that the boiling point of the products was above their thermal stability point and it was not possible to readily isolate the products by distillation.  
  Chlorobenzene, vinyl chloride, allyl chloride. 2-chloro-Z-methylpropane. neopentylchloride and dichloromethane were all reacted in a similar manner to that disclosed in the above examples. While in most instances the desired products were formed, complex reaction byproducts were also formed.  
 Effect of Adding PSCl When PSCl is added to the reaction mixture of alkyl chloride and phosphorus pcntasulfide the normal reaction product (RS) P(S)Cl is converted to RSP(S )(1 as shown in the equation below:  
  The conversion can also be effected after the initial reaction of the alkyl chloride and phosphorus pentasulfide by reacting PSCl with the reaction mixture or the isolated monochloride product. The conversion occurs at temperatures as low as C. but it is preferred to utilize temperatures above about to about 300C. The conversion of the monochloride product to the dichloride is represented by the equation set forth below:  
 (RS) P(S)Cl PSCl 2RSP(S)C1 1f the product desired is the dichloride, there is an obvious advantage to employing a one-step conversion instead of the two-step process. Since the reaction is an equilibrium system, it is desirable to add excess PSCl to drive the reaction to the dichloride product.  
 EXAMPLE 15 Reaction with Methyl Chloride Employing PSCl The 300 ml. stainless steel autoclave used in Example 1 was chargedwith 37.5 grams of methyl chloride (0.75  
 mole), 55.5 grams of P 8 (0.125 mole) and 63.5 grams PSCl (0.375 mole 50 percentexcess).  
 The reaction mixture was heated at a temperature of.  
 200C. for a period of 1 hour and at a temperature of 215C. for an additional period of 12 hours.  
 The weight of liquid reaction product recovered from the autoclave was 145 grams (charged weight was.  
 156.5 grams). Analysis by gas chromatograph showed the following compositions:  
 Compound Percentage PCl 7.3 PS0,, 1 1.9 CH;,SP(S)C1 69.4 (CH S) P(S)Cl 9.2 (CH S) PS 0.2  
 EXAMPLE. 16  
 Equilibrium Study PSCl (CH S) P(S)Cl 2 2 CH SP(S)C1 A 2.83 gram portion of (Cl-l S) P(S)Cl (0.155 mole) and 2.61 grams of PSCl (0.155 mole) were sealed in a glass carius tube. The sample was heated to 130C. for 233 hours after which no change occurred on further heating. Analysis of the product indicated it contained 0.50 grams of unreacted (Cl-l P(S)Cl and 4.65 grams of CH SP(S)CI Also remaining in the reaction mixture was about 0.4 grams of unreacted PSCl What is claimed is:  
  1. A process for the preparation of monoand dialkyl-; monoand dicyc1ohexyl-; and monoand dibenzyl-mercapto phosphorothionochloridates which comprises heating a mixture of a chloride selected from the group consisting of lower alkyl chlorides containing from about 1 to about 8 carbon atoms inclusive, cyclohexyl chloride or benzyl chloride and phosphorus pentasulfide at an effective temperature in the range from about 160 to about 300C., said effective temperature dependent upon the particular chloride employed, for a length of time sufficient to effect reaction.  
  2. The process of claim 1 wherein said chloride is methyl chloride.  
  3. The process of claim 1 wherein the temperature is from 200 to 300C.  
  4. The process of claim 1 wherein said chloride is ethyl chloride. 7  
  5. The process of claim 1 wherein said chloride is 2- chloropropane.  
  6. The process of claim 1 wherein said chloride is lchloropropane.  
  7. The process of claim 1 wherein said chloride is benzyl chloride.  
  8. A process for preparing monoalkyl-; monocyclohexylor monobenzyl-mercapto phosphorothionochloridate which comprises heating a mixture of a chloride selected from the group consisting of alkyl chlorides containing from about 1 to about 8 carbon atoms inclusive, cyclohexyl chloride or benzyl chloride; phosphorus pentasulfide and thiophosphoryl chloride at an effective temperature in the range of from about 160 to about 300C. said effective temperature dependent upon the particular chloride employed for a length of time sufficient to effect reaction.  
  9. The process of claim 8 wherein said chloride employed is methyl chloride.  
  &#39;10. The process of claim 8 wherein the temperature is from about 200 to about 300C.  
  11. The process of claim 8 wherein said chloride is ethyl chloride.  
  12. The process of claim 8 wherein said chloride is 2-chloropropane.  
  13. The process of claim 8 wherein said chloride is l-chloropropane.  
  14. The process of claim 8 wherein said chloride is benzyl chloride.  
  15. A process for preparing monoalkyl-; monocyclohexylor monobenzylmercapto phosphorothionodichloridate wherein a mixture containing monoalkyl-, the alkyl group containing from about 1 to about 8 carbon atoms inclusive; monocyclohexylor monobenzylphosphorothionodichloridate and dialkyl-, each alkyl group containing from about 1 to about 8 carbon atoms inclusive; dicyclohexylor dibenzylphosphorothionochloridate is reacted with thiophosphoryl chloride at a temperature between about and about 300C for a sufficient length of time to form monoalkyl-; monocyclohexylor monobenzylmercapto phosphorothionodichloridate.  
  16. The process of claim 15 wherein the alkylmercapto group is methylmercapto.  
  17 The process of claim 15 wherein the temperature is from about to about 300C.  
  18. The process of claim 15 wherein the alkyl mercapto group is ethyl mercapto.  
  19. The process of claim 15 wherein the alkyl mercapto group is 2-propylmercapto.  
  20. The process of claim 15 wherein the alkyl mercapto group is l-propylmercapto.  
  21. The process of claim 15 wherein the mercapto group is benzyl mercapto.  
  22. A process for preparing monoalkyl-; monocyclohexylor monobenzylmercapto phosphorothionodichloridate which comprises heating a mixture containing dialkyl-, the alkyl group containing from about 1 to about8 carbon atoms inclusive; dicyclohexylor dibenzylphosphorothionochloridate and thiophosphoryl chloride at a temperature between about 100 and about 300C. for a sufficient length of time to form monoalkyl-; monocyclohexylor monobenzylmercapto phosphorothionodichloridate.  
  23. The process of claim 22 wherein the alkyl mercapto group is methyl mercapto.  
  24. The process of claim 22 wherein the temperature is from about 130 to about 300C.  
  25. The process of claim 22 wherein the alkyl mercapto group is ethyl mercapto.  
  26. The process of claim 22 wherein the alkyl mercapto group is 2-propylmercapto.  
  27. The process of claim 22 wherein the alkyl mercapto group is l-propylmercapto.  
  28. The process of claim 22 wherein the mercapto group is benzyl mercapto.