3,074,994 United States Patent Office Patented Jan. 22, 1963 2 vantage thereto, sub-atmospheric pressures are contem 3,074,994 lated. METHOD OF PREPARENG DCHLORDES p The process of the present invention may be carried PRIMARY PHOSPENE out in a batch, continuous or semi-continuous method. Martin Grayson, Norwalk, Conn., assignor to American 5 Usually agitation of the reactants provides better inter Cyanamid Company, New York, N.Y., a corporation mingling and more rapid reaction rates. of Maine The primary aliphatic phosphines contemplated herein No Drawing. Fied Apr. 7, 1960, Ser. No. 20,565 have from 1 to 20 carbon atoms in their alkyl moieties. 4. Claims, (C. 260-464) Insofar as substituents on the alkyl moieties are con cerned, cyano, halogen, lower alkoxy, carbethoxy, and The present invention relates to a novel method of 10 the like, are typical. This applies to cycloalkyl also. halogenating primary phosphines. More particularly, The present invention will best be understood in the the instant discovery concerns the reaction of phosgene light of the following examples, in which product yields with primary phosphines to provide the corresponding on the order of about 45 to about 70 percent by weight alkyl dichlorophosphines. are realized: In 1879 Michaelis and Dittler (Ber. 12, 338) reported 5 Example I that arylphosphines, namely phenylphosphine, could be CHC NC CH CEPH -- 2COCl. --> reacted at elevated temperatures with phosgene gas to -60° C. produce very desirable yields of the corresponding di 2CO - 2HCl -- NCCHCHP Cla chlorophenylphosphine. 20 Since then attempts to convert primary aliphatic and 2-cyanoethylphosphine. (24 grams, 0.25 mole) is added cycloaliphatic phosphines, substituted or unsubstituted, to to 102 grams (1.03 mole) of phosgene condensed into their corresponding dichloro-derivatives following the 350 milliliters of chloroform at a temperature of -60 Michaelis and Dittler process have not been successful. C. to -50° C. over a period of 2.5 hours. The mixture For example, repeating the Michaelis and Dittler process 25 - is warmed slowly (4 hours) to -20° C. and then to room using cyanoethylphosphine NCCH2CH2PH2 in lieu of temperature. After removing phosgene and solvent, the phenylphosphine provides yields of dichloro-2-cyanoethyl liquid product boils at 89 C. at 2.5 millimeters (Hg) phosphine NCCH2CH2PCl2 of only about 13 percent. pressure and weighs 22 grams. The reason for such low yields is not understood. Example II According to the present invention, however, it has 30 CCECEIC been found that primary alkylphosphines and primary CH3CE2 CEPH2 -- 2CO Cls - - - cycloalkylphosphines, substituted and unsubstituted, may -10° C. be reacted with liquid phosgene at temperatures in the 2CO -- 2HC -- CH3CHCHF Ci range of 8 C. to -80° C., preferably -10° C. to in-Propylphosphine (0.25 mole) is added to phosgene -60° C., to provide product yields 400 to 500 percent (0.55 mole) dissolved in 150 milliliters of ethylene di greater than those provided by the process taught by chloride at -10° C. over a period of one hour. The Michaelis and Dittler. product mixture is warmed to ambient temperature, According to a preferred embodiment, the alkylphos filtered to remove solid by-products, and dichloro-n-pro phine is added to the phosgene, the latter being dissolved pylphosphine is recovered by distillation. in an inert organic solvent, such as chloroform; the tem 40 perature of the resulting mixture is maintained at about Example III -40 C. to -60° C. until reaction ceases. While it is C6He CH3(CH2)7PH -- 20 O Cle ---> not necessary that the phosphine reactant be added to 200 C. the phosgene (COCl), it is essential that at almost any 2CO -- 2HCl -- CH3(CH2)P Cl given time during the reaction the phosgene reactant be in-Octylphosphine (1.0 mole) is added to phosgene present in at least stoichiometric amounts or, preferably, (3.0 mole) dissolved in 500 milliliters of benzene in a in at least a slight excess, relative to the phosphine one-liter glass-lined autoclave at 120° C. and autogenous reactant.Among the many inert organic solvents contemplated pressure over a period of one-half hour. The reaction herein, i.e., solvents which are inert with respect to the 50 mixture is agitated for an additional hour at 120° C., reactants and the reaction product under the conditions cooled to ambient temperature, and the product dichloro of the reaction, are ethers and various chlorinated hydro n-octylphosphine recovered by distillation. carbons in which, generally, both the phosgene and the Example IV phosphine reactant are soluble, thus providing a homo CHCI geneous reaction mixture. Typical solvents are chloro form, trichloroethylene, tetrahydrofuran, dioxane, and CICH, CH, CH, PH, + 2COCl, 0° C. the like. 2CO - 2.HCl -- CICH2CHCHP Cl A Wide variety of primary phosphine reactants is con 3-chloropropylphosphine dissolved in chloroform is fed templated herein, and the following are typical: 2-cyano simultaneously to a mixing zone at 0° C. with a solution ethylphosphine, octylphosphine, 3-chloropropylphosphine, 60 of phosgene in chloroform at 0° C. The molar ratio of 3-ethoxypropylphosphine, 2-carbethoxyethylphosphine, n 3-chloropropylphosphine to phosgene is maintained at 1 octadecylphosphine, cyclohexylphosphine, 4-chlorocyclo to 2 and the product stream is fed continuously to a hexylphosphine, 3-ethoxycylohexylphosphine, 3-cyano Stripping device for removal of solvent. Crude dichloro cyclohexylphosphine, and the like. 3-chloropropylphosphine is recovered. Subsequent dis Although atmospheric pressures are generally contem 65 tillation of this crude product gives a pure material. plated herein, it has been found that super-atmospheric Example V pressures may be employed successfully. It will be noted, however, that at Super-atmospheric pressures proportion CHOCH2CHCH, PH + 2COCl. . CC. . ately higher temperatures may be employed, providing, -20° C. of course, the COCl remains in the liquid state. Ex 70 2CO -- 2HCl -- CHO CHCHCHP Cl ample III, infra, demonstrates this fact. 3-ethoxypropylphosphine (0.10 mole) is added to a Likewise, while there appears to be no apparent ad solution of 0.60 mole of phosgene in 100 milliliters of 3,074,994 4. carbon - tetrachloride. at -20° C. in two hours. The . Clearly, the instant discovery encompasses numerous mixture is permitted to warm to ambient temperature in modifications within the skill of the art. Consequently, a stream of dry nitrogen, filtered, and subjected to distill while the present invention has been described in detail lation to recover dichloro-3-ethoxypropylphosphine. with respect to specific embodiments thereof, it is not in Example VI tended that these details be construed as limitations upon CEO the scope of the invention, except insofar as they appear CHO, CCH, CH, PH2 + 2COCl, --> in the appended claims. -50° C. i claim: 2CO - 2ECi -- Cal-Is OCCH2CH2PCi2 1. A method of preparing chlorinated phosphines O which comprises bringing together into reactive contact A solution of 2-carbethoxyethylphosphine (0.25 mole) a member selected from the group consisting of a pri in 50 milliliters of tetrahydrofuran is added in two hours mary alkylphosphine having up to 20 carbon atoms, a to a solution of phosgene (1.0 mole) in 200 milliliters of substituted primary alkylphosphine having up to 20 car tetrahydrofuran at -50 C. After warming to ambient bon atoms, a primary cyclohexylphosphine, and a sub temperature, the solution is filtered and then distilled. stituted primary cyclohexylphosphine, and liquid phos Dichloro-2-carbethoxyethylphosphine is thus recovered. gene at a temperature in the range of 8 C. to -80 C. Example VII and recovering the resulting corresponding dichlorophos Example III, above, is repeated in every essential re phine selected from the group consisting of dichloro spect with the exception that n-octadecylphosphine is alkylphosphine, dichloro-alkylphosphine in which the used in lieu of n-octylphosphine and dichloro-n-octadecyl 20 alkyl moiety is substituted, dichloro-cyclohexylphosphine, phosphine recovered. and dichloro-cyclohexylphosphine in which the cycloalkyl moiety is substituted, said substituents on the alkyl and Example VIII cyclohexyl reactants and products being selected from Example I, above, is repeated in every essential respect the group consisting of cyano, chloro, lower alkoxy and only the phosphine reactant is replaced and the corre 25 carbethoxy. sponding product recovered: 2. The process of claim 1 wherein the primary phos phine is added to the liquid phosgene. 3. The process of claim 1 wherein the reactants are Reactant Product brought together in the presence of an organic solvent 30 inert with respect to the reactants and their correspond cyclohexylphosphine------dichlorocyclohexylphosphine. ing reaction products under the conditions of the reaction. 4-chlorocyclohexylphosphine-...-- districlorocyclohexylphosphine. 4. The process of claim 1 wherein the liquid phosgene 3-ethoxycyclohexylphosphine------disgrihoxycyclohexyl is present in at least stoichiometric amounts relative to 3-cyanocyclohexylphosphine-...--- dichloro-3-cyanocyclohexylphospinne. phosphine. the phosphine throughout substantially all of the reaction. 35 References Cited in the file of this patent The halogenated compounds of the present invention UNITED STATES PATENTS have direct utility as gasoline additives. For example, 2,437,796 Walling ------Mar. 16, 1948 up to about 10 milliliters of a mixture of any one of : these halogenated phosphines added to 1 gallon of gaso 40 OTHER REFERENCES line affords protection against misfiring, surface ignition, Michaelis: Ber. Deut. Chem., vol. 12, pp. 338-340 and the like. - (1897). (Copy of above in Patent Office Library.)