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1. (WO1979000172) PROCEDE DE PRODUCTION DE DIALKYL PHOSPHOROCHLOROTHIONATES PURS
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PROCESS FOR MANUFACTURING SUBSTANTIALLY
PURE DIALKYL PHOSPHOROCHLORIDOTHIONATES

BACKGROUND OF THE INVENTION
This invention relates to a process for
producing in high yields substantially pure phosphorochloridothionate (hereinafter "thionate").
The thionates produced by the process of this invention have the general formula:



wherein R1 and R2 are each alkyl substituents of 1 to
12 carbon atoms. The thionates are valuable intermediates in the manufacture of.pesticidal agents, flotation agents, plasticizers, lubricating oil additives, rubber curing compounds, flame retardants and many other useful
chemicals.
Various processes have been utilized for the production and purification of the aforementioned thionates for example:
(1) U.S. Patent 3,897,523 to Sorstokke;
(2) U.S. Patent 3,794,703 to Beck et al;
(3) U.S. Patent 3,502,750 to Anglaret;
(4) U.S. Patent 3,356,774 to Niermann et al;
(5) U.S. Patent 3,098,866 to Divine;
(6) U.S. Patent 3,089,800 to Chupp et al;
(7) U.S. Patent 2,900,406 to Vogel et al;

(8) U.S. Patent 2,715,136 to Toy et al;
(9) U.S. Patent 2,692,893 to Hechenbleikner;
(10) U.S. Patent 2,482,063 to Hechenbleikner;
(11) British Patent 646,188 to Hechenbleikner;
(12) British Patent 1,289,396 to Hercules, Inc; and (13) German Patent 1,801,432 to Knapsack, Ag.
The entire disclosures of all of the aforementioned references are incorporated herein by
reference.
Generally, commercial quantities of thionates are obtained by chlorinating an initial reactant composition with a chlorinating agent, the reactant composition containing at least one compound which is either:
(l) A bis(phosphorothioic) sulfide of the general formula:



wherein m is a whole number, preferably 2; or
(2) a thioic acid or salt thereof having the general formula:



wherein M is hydrogen, ammonium, an alkaline earth metal or an alkali metal. The chlorinating step produces a crude thionate reaction mixture which contains the thionate and impurities. The crude reaction mixture is usually purified.
The chlorinating agents which can be employed include chlorine, sulfur dichloride, sulfur monochloride, sulfuryl chloride and phosphorus pentachloride.

A process for producing a thionate by
chlorinating a bis (phosphorothioic) sulfide is more fully described in, for example, the aforementioned
U.S. Patent 2,482,063 to Hechenbleikner.
A process for producing a thionate by
chlorinating a thioic acid or salt thereof is more fully described in, for example, the aforementioned U.S. Patent 2,692,893 and British Patent 646,188 to Hechenbleikner.
As indicated the aforementioned processes produces by-product impurities. Illustrative of some of the processes employed to produce thionates are the by-product impurities produced therefrom are the
following, wherein M is as previously defined an0
wherein X is the grouping


ReacChlorinThion- By-Product
tant ating ate Impurities
Agent
(a ) 2XSM + 3Cl2 → 2 XCl + 2MCl + S2Cl2
(b ) 2XSM + 2Cl2 → 2 XCl + 2MCl + 2S
(c ) 2XSM + 2S2Cl2 → 2 XCl + 2MCl + 6S
(d ) 2XSM + 2SCl2 → 2 XCl + 2MCl + 2S
(e ) 2XSM + 6Scl2 → 2 XCl + 2MCl + 4S2Cl2
(f ) 2XSM, + 2SO2Cl2 → 2 XCl + 2MCl+2S+2SO2
(g ) 2XSM + Cl2 → (X)2S2 + 2MCl
(h ) 2XSM + S2CI2 → (X)2S4 + 2MCl
(i ) 2XSM + 2Cl2 → (X)2S2+2MCl+S2Cl2
(j ) 2XSM + SO2Cl2 → (X)2S2+2MCH-SO2
(k ) (x)2S 2 + 2Cl2 → 2 XCl + S2Cl2
(l ) (x)2S 2 + Cl2 → 2 XCl + 2S
(m) (x)2S 2 + S2Cl2 → 2 XCl + 4s
(n) (x)2S 2 + 4SCl2 → 2 XCl + 3S2Cl2
(o ) (x)2S 2 + SO2Cl2 → 2 XCl + 2S
(p ) (X)2S2 + 2SO2Cl2 → 2 XCl + S2Cl2+2SO2
(q) (x)2S 3 + S2Cl2 → 2 XCl + 5S
( r ) (x)2S 4 + S2Cl2 → 2 XCl + 6S

/^_ R
' OM For example, in a typical type (k) reaction
bis (O,O-diethyl phosphorothioic) disulfide is reacted
with chlorine to produce O,O-diethyl chlorothiophosphate as follows:



This reaction produces sulfur monochloride as a by-product impurity.
In a typical type (a) reaction, O,O-diethyl
dithiophosphoric acid is reacted with chlorine to produce O,O-diethyl chlorothiophosphate as follows:



This reaction produces sulfur monochloride and hydrogen chloride as by-product impurities.
Additional impurities may, for example be
introduced if the thionate is produced in a two
step process. A typical two step process involves
treating alcohol with a phosphorus sulfur compound
to produce a crude thioic acid composition:


OMPI wherein, for example, R is an alkyl substituent having from 1 to 12 carbon atoms. The crude thioic acid
reaction mixture is difficult to purify. It is
generally used as the initial reactant composition which is directly chlorinated to produce a crude thionate reaction mixture. The crude thionate reaction mixture produced from this two step process, not only has the by-product impurities produced from the chlorination step, but additionally may have contained therein hydrogen sulfide, unreacted alcohol, or the chlorinated products thereof.
Thus, as can be seen from the foregoing, the crude thionate reaction mixture may have contained therein various quantities of by-product impurities such as
MCI, S2Cl2, S, SO2, (X)2S2, H2S unreacted alcohol, the chlorinated products of H2S and unreacted alcohol,
unreacted XSM and unreacted chlorinating agent from which the thionate must be separated. A substantial portion of the impurities in the crude thionate reaction mixture is usually sulfur monochloride.
In addition, there are a variety of side
reaction impurities which are formed to varying extents depending upon the reaction conditions and the
reactants, i.e. the type and amount of chlorinating.
agent as well as the purity of the bis(phosphorothioic) sulfide or thioic acid or salt thereof subjected to chlorination, which further contaminate the crude
thionate reaction mixture.
For example, the crude thionate
reaction mixture may be additionally contaminated with side reaction impurities some of which satisfy the
structure:


wherein n is O or l, and R is R1 or R2. For example, these side reaction impurities may include one or more compounds having the groups



wherein the unsatisfied valences are satisfied by R1 and/or R2.
The need for improving the quality of the crude thionate reaction mixture is readily apparent in subsequent processes employing the same and in the products derived therefrom. Unless a substantially pure thionate is employed, the efficiency of processes employed in preparing derivatives is substantially lowered. For example, the impurity



(wherein the unsatisfied valence is satisfied by R1 or R2), which may be obtained in substantial amounts from the chlorination process, contains twice as many reactive groups (i.e. chlorine substituents) as the desired thionate. Additionally, this impurity contains the
group which reacts to products which do not


have the desirable properties of the corresponding thionate derivatives.
Many attempts have been made to remove the impurities from crude thionate reaction mixtures in order to produce a purer thionate product, for example:
SOLVENT EXTRACTION TREATMENT
Extraction of the crude thionate reaction mixture with an organic solvent has been utilized to remove impurities. This method is not satisfactory from a commercial standpoint due to the similar
solubility characteristics of the thionate and the associated impurities. Satisfactory separation of
the desired thionate product from the impurities by this technique requires several extractions which
result in losses of the thionate.
WATER CONTACTING/HYDROLYSIS
Separation of sulfur monochloride, from a crude thionate reaction mixture or a distilled crude thionate reaction mixture, can be accomplished by
water hydrolysis. Water hydrolysis can be performed by slowly admixing the crude thionate reaction mixture with water. The sulfur monochloride is hydrolyzed to water soluble acids, i.e. hydrochloric and thiosulfurous, and other products.
Hydrolysis of the sulfur monochloride in the thionate reaction mixture, however produces free
sulfur. The sulfur may take a number of forms including crystals, colloidal particles, or syrupy, plastic semisolids. Particularly in commercial operations, such material causes considerable difficulty in the
separation and recovery of the organic layer containing the thionate.
Additionally, water contacting/hydrolysis treatment does not substantially remove all impurities,
including all of the sulfur monochloride.
DISTILLATION
Removal of impurities, including non-sulfur containing phosphorus compounds, has been attempted by fractional distillation. The method is not satisfactory from a commercial standpoint due to the close proximity of the boiling points of the impurities and the thionate.
A satisfactory separation of the thionate from the impurities by distillation is not possible unless repeated several times. Thionate yields may be reduced by reaction of sulfur monochloride with the thionate
at high distillation temperatures. Additionally,
at elevated temperatures other side reactions can occur which cause the formation of sulfur which can cause
fouling of the distillation apparatus.
THIOIC ACID TREATMENT
Another method for purifying crude thionate reaction mixtures is admixing and reacting a dialkyl
phosphorodithioic acid with the crude thionate reaction mixture to react with some of the impurities to form
additional thionate. The method is not completely
satisfactory since the reaction mixture contains a
substantial amount of impurities which do not react
with the thioic acid. Additionally, the yield of
thionate based on the total quantity of thioic acid
used is low because the thioic acid which is not
converted to thionate is not recovered. This method of treatment is described in detail in the aforementioned
Beck reference.
None of the aforementioned methods for
treating a crude thionate reaction mixture or known
combinations thereof have been wholly satisfactory in producing high yields of substantially pure thionate.
It is therefore an object of the present
invention to provide a method for the production in.
high yields of a substantially pure thionate.
Further objects and advantages inherent in the present invention will become apparent to those skilled in the art from the following disclosure.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is a process for
producing dialkyl phosphorochloridothionate compounds of the formula :

wherein R1 and R2 are each alkyl substituents of 1 to 12 carbon atoms.
The process is comprised of the following process steps:
(a) chlorinating with a chlorinating agent an initial reactant composition containing at least one compound selected from the group consisting of:
(i) a bis (phosphorothioic) sulfide of the formula:



(ii) a first thioic acid or salt thereof of the formula:



wherein M1 is selected from the group consisting of hydrogen, ammonium, an alkaline earth metal and an alkali metal, to produce a crude thionate reaction mixture containing the thionate and a quantity of
impurities;
(b) distilling the crude thionate reaction mixture to produce an initial thionate distillate
containing the thionate and a lesser quantity of
impurities;
(c) admixing and reacting with the initial thionate distillate a second thioic acid or salt thereof of the general formula:



OM wherein M2 is selected from the group consisting of hydrogen, ammonium, alkaline earth and an alkali metal, to react with at least some of the impurities to produce a semi-pure thionate reaction mixture;
(d) contacting the semi-pure thionate reaction mixture with water to produce an organic phase and a water phase; and
(e) distilling the organic phase to produce a final distillate of substantially pure thionate and a residue fraction.
Unexpectedly, there is substantially, no sulfur precipitation during the contacting step (d).
Preferably, the process further comprises recycling the residue fraction for use as all or part of the initial reactant composition and repeating at least steps (a) and (b), i.e. chlorinating the initial reactant composition and distilling the crude thionate reaction mixture produce therefrom.
It is particularly preferred that the process further comprise recycling the residue fraction for use as all or part of the initial reactant composition and repeating process steps (a) through (e) to produce a final thionate distillate of substantially pure thionate yield.
It is particularly preferred that the process be carried out in a continuous manner.
DETAILED DESCRIPTION OF THE INVENTION
By the use of the term "yields" or "percent yield" it is meant the fraction or percent which the actual quantity of thionate produced is to the
theoretical quantity of thionate that would be produced if all of the bis (phosphorothioic) sulfide or first thioic acid and second thioic acid were converted to thionate.

The term "alkyl substituent", means a mono-valent radical derived from a branched or straight chain saturated hydrocarbon by removal of one hydrogen atom and having the general formula wherein n is a whole


number.
The term "ammonium", means the monovalent
radical -NH4.
The term "alkaline earth metal" means the
elements magnesium, calcium, strontium, barium and radium.
The term "alkali metal" means the elements
lithium, sodium, potassium, rubidium, cesium and
francium. Particularly preferred alkali metals are
sodium and potassium.
As indicated previously, the chlorinating
agents can be chlorine, sulfur dichloride, sulfur
monochloride, sulfuryl chloride and phosphorus pentachloride. A particularly preferred chlorinating agent is chlorine.
Preferably R1 and R2 are the same alkyl
substituents. It is particularly preferred that R1 and R2 be the same alkyl substituents, each being an alkyl substituent of 1 to 8 carbon atoms.
It is preferred that the thioic acid or salt thereof be the same as the second thioic acid or salt thereof, and particularly preferred that M1 and M2 both be hydrogen, i.e. the first thioic acid is the same as the second thioic acid.
It is also preferred that the mole ratio of the quantity of the second thioic acid or salt thereof to the quantity of impurity in the initial thionate
distillate is at least about 0.5:1, and preferably no greater than about 2:1. A mole ratio of about 1:1
is particularly preferred.
It has been found that at mole ratios of less than about 0.5=1 sulfur precipitation begins to occur during the contacting step (d).

A mole ratio of greater than about 2:1 becomes economically impractical and unnecessary, although the invention is operative.
Sulfur monochloride as indicated previously is a substantial portion of the total impurities in the crude thionate reaction mixture and is carried over to the initial thionate distillate; therefore the ratio of the quantity of the second thioic acid or salt
thereof to the quantity of sulfur monochloride impurity in the initial thionate distillate should preferably be at least about 0.5:1 and preferably no greater than about 2:1. A mole ratio of about 1:1 is particularly preferred.
A particularly preferred embodiment of the process of this invention is a process for producing in high yields a substantially pure thionate compound of the general formula:



wherein R3 is an alkyl substituent of 1 to 8 carbon atoms. The process is comprised of the following process steps:
(a) chlorinating with chlorine an initial reactant composition containing at least one compound selected from the group consisting of:
(i) a bis (phosphorothioic) sulfide of the formula:



(ii) a thioic acid of the general
formula:


to produce a crude thionate reaction mixture containing the thionate and sulfur monochloride;
(b) distilling the crude thionate reaction mixture to produce an initial thionate distillate containing the thionate and sulfur monochloride;
(c) admixing and reacting with the initial thionate distillate a quantity of the thioic acid sufficient to react with at least some of the sulfur monochloride to produce a semi-pure thionate reaction mixture;
(d) contacting the semi-pure thionate reaction mixture with water to produce an organic phase and a water phase;
(e) distilling the organic phase to produce a final thionate distillate of substantially pure thionate and a residue fraction;
(f) recycling the residue fraction for use as the initial reactant composition and repeating at least steps (a) and (b).
Again, it is particularly preferred that the process further comprise of repeating process steps (c) through (e) to produce a final thionate distillate of substantially pure thionate at high yields.
It is also particularly preferred that the process be a continuous process.
It is preferred that the mole ratio of the quantity of thioic acid admixed and reacted with the initial thionate distillate to the quantity of sulfur monochloride contained therein be at least about 0.5:1 and preferably no greater than about 2:1. A mole ratio of about 1:1 is particularly preferred.
The process of this invention is particularly suited for producing in high yields, substantially pure dimethyl and diethyl phosphorochloridothionate.
More specifically, chlorinating the initial reactant composition is accomplished by known methods in the art, for example as described in the aforementioned Hechenbleikner references.
Suitable inert organic solvents may be employed in the process. Such solvents include carbon tetrachloride, chloroform, benzene, toluene, xylene, chlorobenzene, tetrachloroethane, methylene chloride, ethylene dichloride and the like. It is preferred however that no solvent be used during the chlorination.
The chlorination is preferably carried out at a temperature within the range of from about 0° to 80°C. However, temperatures outside this range may be employed depending upon the type of reactants utilized. Cooling means may be necessary, since the reaction is somewhat exothermic, particularly in the early stages.
It has unexpectedly been found that lower
chlorination temperatures may be utilized, i.e. about
40°C. and below, without causing sulfur precipitation during the contacting step (d) while still maintaining high yields of substantially pure thionate product.
Distillation of the crude thionate reaction mixture (step (b)) and the organic phase (step (e)) are accomplished by known methods in the art. The distillation is generally carried out under reduced pressure.
Distillation of the crude thionate reaction mixture substantially separates the impurities from
the crude thionate reaction mixture to produce an
initial thionate distillate containing the thionate and a lesser quantity of impurities. As indicated previously, a substantial portion of the impurities in the initial thionate distillate is sulfur monochloride. The
residue from the distillation consists of higher
boiling impurities.
Distillation of the organic phase, produced by contacting the semi-pure thionate reaction mixture with water, separates impurities and water from the
thionate to produce a final thionate distillate of substantially pure thionate. The residue fraction containing higher boiling impurities can be recycled to the chlorination step (a). A substantial portion of the residue fraction will be the bis(phosphorothioic) sulfide of formula (2).
More particularly, the crude thionate reaction mixture or the organic phase is subjected to distillation to remove low boiling materials which are characteristic of the particular chlorinating reaction (step (a)) or admixing and reacting (step (c)), i.e. hydrogen chloride, hydrogen sulfide, sulfur dioxide, alkyl chlorides, inert organic solvents, and the like, which boil below the boiling point of the desired thionate. Subsequently, the thionate distillate is produced by distilling the remainder under reduced pressure.
Distillation may be accomplished by a wiped film evaporator, wherein a vaporous fraction containing the thionate is formed and separated from a residue fraction containing relatively non-volatile material. The vaporous fraction is emitted from the evaporator to a condenser. The residue is discharged from the evaporator as a liquid.
The residue from distilling step (b) and residue fraction from distilling step (e) may be transferred to, for example, a by-product recovery system where the residue material may be converted to useful products such as phosphoric acid and sulfur.
Optionally, the residue fraction from distilling step (e) may be recycled to be utilized as the initial reactant composition for chlorinating wherein the
bis(phosphorothioic) sulfide and/or thioic acid is converted to thionate.
Distillation of the crude thionate reaction mixture produces an initial thionate distillate which is then admixed and reacted with a thioic acid or salt thereof (step (c)).

The process step of admixing and reacting the initial thionate distillate with a quantity of a thioic acid or salt thereof is preferably accomplished by adding the thioic acid or salt thereof to the initial thionate distillate and mixing for a period of at least one minute at a temperature of about 10°C. to about 80°C.
It is essential that the alkyl substituents of the second thioic acid or salt thereof correspond to the alkyl substituents of the thionate being produced. Thus, for example, if the process is being utilized to produce dimethyl phosphorochloridothionate, dimethyl phosphorodithioic acid or its salt thereof is utilized. Likewise, if the process is leing utilized to produce diethyl phosphorochloridothionate, diethyl phosphorodithioic acid or its salts thereof is utilized.
A sufficient quantity of thioic acid or salt thereof is added to react with at least some of the impurities in the initial thionate distillate to produce a semi-pure thionate reaction mixture.
Unexpectedly, it has been found that upon subsequently contacting the semi-pure thionate reaction mixture with water, the sulfur precipitate which
usually accompanies such contacting is eliminated.
Generally, the second thioic acid or salt thereof may be added to the initial thionate distillate in a quantity such that the mole ratio of the second thioic acid or salt thereof to the quantity of
impurities in the initial thionate distillate is at least about 0.5:1 and preferably no greater than about 2:1. It is particularly preferred that the mole ratio be about 1:1.

The quantity and type of impurities in the
initial thionate distillate can be readily determined by methods well known in the art, i.e. KI method for determining sulfur monochloride (see, for example,
"Studies in the Chemical Behavior of Some Compounds of Sulfur", Proceedings of the Indian Academy of Science, 1953, Pages 17-22).
It has been found that sulfur monochloride is the predominant impurity contained in the initial
thionate distillate. The quantity of sulfur monochloride may be used to determine the quantity of second thioic acid or salt thereof required. The mole ratio of the thioic acid or salt thereof to the sulfur
monochloride in the initial thionate distillate should be at least about 0.5:1 and preferably no greater than 2:1. It is particularly preferred that the mole ratio be 1:1.
Generally, the length of time for which the thioic acid or salt thereof is admixed with the initial thionate distillate depends upon various factors, i.e.
batch size, mixing procedure, impurities, temperature and the like.
It has been found however, that a period of about 1 minute to about 1 hour is sufficient for the thioic acid or salt thereof to react with at least
some of the impurities.
The addition of the thioic acid or salt thereof to the initial thionate distillate may be accomplished at from about 10°C. to about 80°C. It is preferred
however that the temperature be from about 20°C. to
about 45°C
The admixing and reacting of the thioic acid or salts thereof with the initial thionate distillate produces a semi-pure thionate reaction mixture which is then contacted with water [step (d)] reaction mixture with water is both a hydrolysis process and a liquid-liquid extraction process.
The contacting step comprises contacting the semi-pure thionate reaction mixture with water and thereafter separating the organic and aqueous phases. The temperature of contacting with water can vary widely, e.g. 5°C. to 75°C., but is preferably conducted in the range of from about 10°C. to about 50°C. The time of contacting and the amount of water utilized can also vary depending upon the amount of impurities, the improvement in quality or up-grading desired, the available equipment, the rate and type of contacting (e.g., simple shaking, bubbling water up through the composition, counter-current or concurrent flow,
mechanical agitation, the temperature of contacting, and the like). In other words, the time or duration of contact between the water and the semi-pure thionate reaction mixture and the amount of water utilized will be dictated by the designs of the manufacturer. In general, the time for contacting should be as short as required to achieve the desired degree of upgrading.
In general, the amount of water utilized will be in the range of 0.1 to 10 volumes of water for each volume of semi-pure thionate reaction mixture. In a one-stage contact operation about 0.25 to about 2.5 volumes of water for each volume of semi-pure thionate reaction mixture constitute a satisfactory ratio.
The water in- which some of the impurities are soluble forms an aqueous phase and the thionate is contained in an organic phase. The two phases are separated and the water phase transferred to, for example, a by-product recovery system. The organic phase is then distilled [step (e)].
The distilling of the organic phase is, as previously described, accomplished by methods well known in the art.

In order to produce substantially pure thionate in high yields it is particularly preferred that the residue fraction from the distilling step (e ) be recycled for use as the initial reactant composition in the
chlorinating step and subsequently performing at least the step of distilling. Preferably the distillate from this distilling step is subjected to the admixing and reacting step, the contacting step and the distilling step.
The initial reactant composition used in the chlorinating step may not only consist of the recycled residue fraction from step (e) but may consist of an additional makeup quantity of bis(phosphorothioic)
sulfide or thioic acid or salt thereof.
In a continuous type operation the residue fraction from distilling step (e) may be continuously recycled for use as the initial reactant composition and a makeup quantity of bis(phosphorothioic) sulfide or thioic acid or salt thereof continuously added thereto.
As indicated previously, it has unexpectedly been found that the addition of the second thioic acid or salt thereof to the initial thionate distillate not only increases the final yield of thionate when the residue fraction is recycled, but also eliminates the sulfur precipitate which usually accompanies the water contacting/hydrolysis treatment.
Further, the process of this invention is an improvement over the prior art processes in that the whole or a part of the chlorination step can be
completed at lower temperatures, i.e., 40°C. and below without sulfur precipitation in the contacting step (d), decreased purities or decreased yields. Lower temperatures favor the formation of sulfur monochloride, and reduced sulfur precipitation during chlorination, but do not favor the formation of other by-product impurities.
Chlorinating at low temperatures (thus producing increased quantities of sulfur monochloride) in combination with only thioic acid treatment would necessitate the use of large quantities of thioic acid to

react with the sulfur monochloride. Such large
quantities of thioic acid would be essentially wasted without a method of recycling the reacted or unreacted thioic acid.
Chlorinating at low temperatures in combination with only the water contacting/hydrolysis
treatment would result in the precipitation of copious quantities of sulfur due to the reaction of the sulfur monochloride with water.
Surprisingly and unexpectedly admixing and reacting the thioic acid or salt thereof with the
initial thionate distillate results in the conversion of the sulfur monochloride impurity to a bis (phosphorothioic) sulfide which does not cause precipitation of sulfur upon contacting with water and can be recycled for chlorination to the desired thionate.
Thus, as can be seen from the foregoing, the process of this invention is particularly advantageous over prior art processes in that thionate yields and purity are increased under more favorable process
reaction conditions.
The following are non-limiting examples of the process of this invention which will give a more complete understanding of the invention and its
advantages.

EXAMPLE 1
DIMETHYL PHOSPHOROCHLORIDOTHIONATE
A 5°0 ml flask was charged with 158 grams
(1 mole) of dimethyl phosphorodithioic acid. The thioic acid was heated to 60°C. and 77 grams (1.08 mole) of chlorine were bubbled into the mixture for a period of two hours to produce a crude thionate reaction mixture.
The crude thionate reaction mixture was distilled in a wiped film evaporator at a skin temperature of
90-95°C. under 5 mm vacuum. The initial thionate
distillate produced (135.7 grams) was analyzed, by the KI titration method, and found to contain 6.9% by
weight sulfur monochloride (.070 moles).
To a stirred solution of 134 grams of the
initial thionate distillate, 13.0 grams of dimethyl phosphorodithioic acid (.082 moles) were added slowly, while maintaining the temperature below 45°C.
The resultant semi-pure thionate reaction
mixture was stirred for 15 minutes, then added slowly with agitation to 105 ml. distilled water. The organic layer was separated and redistilled to produce a final thionate distillate. The distillate, 102.1 grams, was analyzed and found to be more than 99% dimethyl
phosphorochloridothionate. The residue fraction, 19.5 grams was a brown oil.
A 500 ml flask was then charged with 158 grams (1 mole) of dimethyl phosphorodithioic acid and 16.2 grams of the brown residue fraction. While this
solution was stirred at 60°C. to 65°C, 81.3 grams
(1.14 moles) of chlorine was bubbled into the mixture for a period of 2 hours to produce a crude thionate reaction mixture. Distillation of this crude thionate reaction mixture yielded 144 grams of an initial thionate distillate containing 6.0% S2Cl2 (.064 moles). T) 141,5 grams of this distillate was added 12.0 grams (.76 moles) of dimethyl phosphorodithioic acid. The resultant mixture was hydrolyzed with 120 grams of water and redistilled. The final thionate distillate 113.0 grams was analyzed and found to be more than 99% dimethyl phosphorochloridothionate. The residue, 16.7 grams was retained for further recycling.

EXAMPLE 2
DIETHYL PHOSPHOROCHLORIDOTHIONATE
A 5°0 ml flask was charged with 186 grams
(1 mole) of diethyl phqsphorodithioic acid. The thioic acid was heated to 60ºC. and 77 grams (1.08 mole) chlorine was bubbled into the mixture for a period of two hours to produce a crude thionate reaction mixture.
The crude thionate reaction mixture was distilled as in Example 1 yielding l6l.6 grams of an
initial thionate distillate containing impure diethyl phosphorochloridothionate. The distillate contained 2.2% S2Cl2 (.026 moles). To a stirring solution of 159 grams of the distillate at ambient temperature was added 9.5 grams of diethyl phosphorodithioic acid (.051 moles).
The resultant mixture was added slowly to 126 grams of water. After separation of the two phases, the organic phase was distilled yielding 138.0 grams of greater than 99% pure diethyl phosphorochloridothionate. The residue fraction was 13.1 grams of a brown oil.
Another 186 grams of diethyl phosphorodithioic acid was added to 11.4 grams of the residue fraction and the mixture was chlorinated as above, with 8l grams of chlorine (1.14 moles). Distillation yielded 170.8 grams of an initial thionate distillate. The initial thionate distillate contained 2.1% S2Cl2 (.027 moles). Addition of 9.9 grams of diethyl phosphorodithioic acid (.053 moles) followed by water washing and distillation resulted in 145.5 grams of greater than 99% pure diethyl phosphorochloridothionate and 13.1 grams of recyclable residue. Overall yield based on chlorinated thioic acid was 74.4%.

EXAMPLE 3
WATER WASHING OF DIMETHYL PHOSPHOROCHLORIDOTHIONATE (DMPCT) - SULFUR MONOCHLORIDE
MIXTURES
Three solutions of DMPCT containing 10% by weight S2Cl2 were prepared. One solution was water washed and redistilled without further treatment. The other two solutions were treated with dimethyl phosphorodithioic acid (DMPTA) as described in Example 1. The results presented in the table below demonstrate the increased DMPCT obtained in the treated samples and the elimination of sulfur precipitate in the water contacting step. There was no recycle of the residue fraction.
TABLE I

DMPTA ADDITION AND WATER-WASH
OF SpClp-DMPCT MIXTURES

BLANK RUN 2 RUN 3

Wt. Ratio DMPCT: S2Cl2 300 :33 300 :33 300 :33

Wt. of DMPTA Added None 78 g. 39 g. Mole Ratio DMPTA :S2Cl2 - 2 :1 1 :1

Wt. of Sulfur Precipitate 7.2 g . 0 0
Wt. of Final Thionate
Distillate 270 g. 277 g. 278 g .

Assay Final Thionate
Distillate (% DMPCT) 99% 99% 99%

Wt. Residue Fraction 21 g . 89 g. 57 g .

EXAMPLE 4
DIMETHYL PHOSPHOROCHLORIDOTHIONATE
A 500 ml flask was. charged with 158 grams
(1 mole) dimethyl phosphorodithioic acid. The thioic acid was heated to 60°C. and 56 grams (.788 moles) of chlorine was bubbled into the mixture for a period of 1.5 hours to produce a reaction mixture which was then cooled to 35°C. 26 grams (.366 moles) of chlorine was additionally bubbled into the mixture for a period of 0.5 hours to produce a crude thionate reaction mixture.
The crude thionate reaction mixture was
distilled through a wiped film evaporator at a skin temperature of 9°-95°C. under 5 mm Hg. vacuum. The initial thionate distillate produced was 162.8 grams and was analyzed by Ki titration method and found to contain 11.5% by weight sulfur monochloride (0.14 moles).
To a stirring solution of l6θ grams of the initial thionate distillate, 25 grams of dimethyl
phosphorodithioic acid (0.l6 moles) was added slowly, while maintaining the temperature below 45°C.
The resultant semi-pure thionate reaction mixture was stirred for 15 minutes, then added slowly with agitation to 150 ml distilled water. The organic layer was separated and distilled to produce a final thionate distillate. This distillate, 114.1 grams was analyzed and found to contain greater than 99% dimethyl phosphorochloridothionate. The residue fraction, 41.8 grams was a brown oil.
A 500 ml flask was then charged with 158 grams (1 mole) of thioic acid and 38 grams of the brown
residue fraction. While this solution was stirred at 60°C. to 65°C, 58 grams (.816 moles) of chlorine was bubbled into the mixture for a period of 1.5 hours to produce a reaction mixture which was then cooled to
35°C. 30.7 grams (.432 moles) of chlorine was additionally bubbled into the mixture for a period of 0.5 hours to produce a crude thionate reaction mixture. Distillation of this crude thionate reaction mixture yielded 179.5 grams of an initial thionate containing 11.6% S2Cl2 (.16 moles). To 178 grams of this distillate was added 29 grams (.18 moles) of dimethyl phosphorodithioic acid. The resultant mixture was hydrolyzed with 150 grams of water and distilled. The final thionate distillate, 121 grams, was analyzed and found to contain greater than 99% dimethyl phosphorochloridothionate. The residue, 53.8 grams was retained for further recycling.