CA1234157A - Process for producing 1,1,2,3-tetrachloropropene - Google Patents

Abstract

ABSTRACT

A process is disclosed for preparing 1,1,2,3-tetrachloropropene comprising contacting 1,1,1,2,3-pentachloropropane with a catalytic proportion of ferric chloride to effect dehydrochlorination of the 1,1,1,2,3-pentachloropropane to produce 1,1,2,3-tetrachloropropene.

Description

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This application is a divisional of copending Application Serial No. ~58,213 filed Jul~ 5, 1984.

Background of the Invention . _ , . .
This invention relates to the preparation of 1,1,2,3-tetrachloropropene and, more particularly, to a novel method for such preparation involving dehydro-chlorination of 1,1,1,2,3-pen-tachloropropane.
1,1,2,3-tetrachloropropene ("Tetra") is an important chemical intermediate useful, for example, in the preparation of the herbicide trichloroallyl diisopropyl thiocarbamate, commonly referred to as "triallate". Conventionally, Tetra is produced by dehydrochlorination oE 1,1,2,2,3-pentachloropropane that is produced in turn by chlorination of 1,2,3-trichloro-propene. While this process provides a generall~satisfactory technical route, the cost of producing the tetrachloropropene depends upon the cost of the trichloropropene raw material.
Smith U.S. patent 3,926,758 describes an alternative route to 1,1,2,3-tetrachloropropene in which 1,2,3-trichloropropane is chlorinated in an open ~essel exposed to u.v. light to produce a mix of chlorinated products containing 20~ to 60~ by weight unreacted 1,2,3-trichloropropane. The chlorinator effluent is separated into five fractions, one of which contains 1,1,1,2,3- and 1,1,2,2,3-pentachloropropanes.
Another fraction containing 1,1,2,3-tetrachloropropane is dehydrochlorinated and then rechlorinated to produce a further fraction containing 1,1,1,2,3- and 1,1,2,2,3-pentachloropropanes. These two pentachloropropanefractions are mixed and subjected to de-~) ~L~39t~5~7

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hydrochlorination to provide a mix of 1,1,2,3- and 2,3,3,3 tetrachloropropenes which is fed to an isomerizer packed with siliceous granules in which the 2,3,3,3-isomer is converted to the 1,1,2,3-isomer.
U.S.S.R. Inventor's Certificate 899,523 describes a somewhat modified process in which 1,2,3-trichloropropane is chlorinated to produce tetrachloro-propanPs; 1,1,2,3 and 1,2,2,3-tetrachloropropanes are extracted from the reaction mixture and further chlori-nated in the presence of dimethylformamide as an initiator to produce pentachloropropanes; 1,1,1,2,3-and 1,1,2,2,3-pentachloropropanes are extracted from the pentachloropropane mixture and dehydrochlorinated to produce a mixture of 1,1,2,3- and 2,3,3,3-tetra-chloropropenes; and the iatter mixture is boiled in the presence of aluminum oxide (at-tapulgite) to isomerize the 2,3,3,3- to the 1,1,2,3- isomer. An overall yield of ~8.19% is reported. The reference describes as prior art a process very close to that o Smith.
An earlier reference by Haszeldine, "Fluoro-olefins. Part II. Synthesis and Reaction of Some

3,3,3-Trihalogenopropenes" Journal of the Chemical Society [1953] pp. 3371-3378, describes a plethora of reactions of products derived from 1,1,1,3-tetra-chloropropane. The reference describes preparation of this intermediate by reaction of carbon tetra-chloride with ethylene in the presence of benzoyl peroxide. Among the numerous syntheses carried out by Haszeldine with 1,1,1,3-tetrachloropropane as the starting material are: dehydrochlorination of this starting material with 10% ethanolic potassium hydroxide to produce a mixture of 3,3,3 and 1,1,3-trichloropropene; isomerization of 3,3,3-trichloro-:. .

.

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propene to l,1,3-trichloropropene using a variety of allylic rearrangement catalysts including antimony fluoride, concentrated hydrochloric acid, concentrated sul~uric acid, aluminum chloride, ferric chloride, ethanolic KOH and anhydrous hydrogen fluoridei chloro-ination OI 1, 1, 3-trichloropropene in the presence of light to produce 1,1,1,2,3-pentachloropropane; chlori-nation of 3,3,3-trichloropropene to produce 1,1,1,2,3-pentachloropropane; dehydrochlorination of 1,1,1,2,3-pentachloropropane with ethanolic potassium hydroxideto produce a mixture of 2,3,3,3-tetrachloropropene and 1,1,2,3-tetrachloropropene; separation of 2j3,3,3-tetrachloropropene from 1,1,2,3-tetrachloropropene by distillation; and isomerlzation of 2,3,3,3-tetrachloro-propene in the presence of aluminum chloride to produce1,1,2,3-tetrachloropropene in 51% yield. Alternatively, Haszeldine discloses thermal isomerization of 2,3,3,3-tetrachloropropene to 1,1,2,3-tetrachloropropene at 180C in 45% yield. Based on the yields reported by ~aszeldine for the above described series of steps, ; the overall yield obtained with his syntheses can be computed as 41.8% based on 1,1,1,3~tetrachloropropane, 10.4% based on carbon tetrachloride.
Asahara et al., "The Telomerization of Ethy-lene and Carbon Tetrachloride", Kogyo Kagaku Zasshi 1971, 74(43, 703-5 discloses telomerization of ethylene and carbon tetrachloride at 130C and at 60-70 x 105 Pa (60-70 atmospheres) pressure in the presence of a triethyl phosphite-ferric chloride hexahydrate catalyst to produce 1,1,1,3-tetrachloropropane. Takamiæawa et al.
U.S. 4,243,607 describes an improvement in the Asahara ~23'~1S7

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process whereby higher yields of l,1,1,3-tetrachloro-propane are obtained by utilizing a catalyst system comprising a nitrile in addition to an iron salt and a trialkyl phosphite.
Japanese Kokai 74-66613 describes a process for producing 1,1,3-trichloropropene by dehydrochlorina-tion of 1,1,1,3-tetrachloropropane using anhydrous FeC13 as a catalyst. Reaction is carried out using 0.2 to 0.6 g FeC13 per mole of 1,1,1,3-tetrachloro-propane at a temperature of 80C to 100C.
A need has remained in the art for improved processes Eor the synthesis of 1,1,2,3-tetrachloropro-pene, especially processes which provide this product in high yield using relatively inexpensive starting materials and which can be operated at modest manu-facturing costs.
Summary of the Invention This invention relates to a process for producing 1,1,2,3-tetrachloropropene comprising contacting 1,1,1,2,3-pentachloropropane with a catalytic proportion of ferric chloride to effect dehydrochlor-ination of the 1,1,1,2,3-pentachloropropane to produce 1,1,2,3-tetrachloropropene.
In an optional embodiment, the process of this invention includes the feature wherein 1,1,1,3-tetra-chloropropane is dehydrochlorinated to produce a mixture of 1,1,3-trichloropropene and 3,3,3-trichloropropene, and prepara-tion of said 1,1,1,2,3-pen-tachloropropane by chlorinating at least one of the trichloropropenes obtained by said dehydrochlorination of 1,1,1,3-tetrachloropropane.
In the above process, the 1,1,1,2,3-penta-chloropropane may be prepared by chlorinating said mixture of trichloropropenes.

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A further optional feature is where the above mixture of 1,1,3-and 3,3,3-trichloropropenes is contacted with a catalyst, the 3,3,3-trichloropropene therein is isomerized to l,1,3-trichloropropene, and 1,1,1,2,3-pentachloropropane is prepared by chlorinating the trichloropropene after the isomerization.
In a still fur-ther optional feature, the above mixture of trichloropropenes is distilled to separate the 1,1,3-trichloropropene from 3,3,3-trichloropropene, and the preparation oE 1,1,1,2,3-pentachloropropane comprises chlorinating at least one of the trichloro-propene Eractions obtained by said distillation.
A still further preferred embodiment of this invention is where the 1,1,1,3-tetrachloropropane is dehydrochlorinated by contacting the 1,1,1~3-tetra-chloropropane with a base in the presence of a phase transfer catalyst at a temperature of between about 40C
and about 80C.
Another optional embodiment is where the 1,1,1,3-tetrachloropropane is prepared by reacting carbon tetrachloride and ethylene in the presence of an active source of metallic iron and a promoter for the reaction.
In the above process, the promoter may be selected from the group consisting of trialkyl phosphites and phosphorus (V) compounds containing a phosphoryl group.

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Description of the Preferred Embodiments In accordance with the present invention, novel processes have been discovered by which 1,1,2,3-tetrachloropropene (Tetra) can be produced with significantly lower manufacturing costs than have been attainable with previously known commercial processes.
Moreover, the processes of this invention provide improved efficiency and yields as compared to other known prior art processes based on 1,1,1,3-tetra-chloropropane. 1,1,2,3-tetrachloropropene produced in accordance with the processes of the invention is of high quality, suitable for use in manufacture of herbicides, pharmaceuticals and other end products.
The 1,1,2,3-tetrachloropropene (Tetra) itselE
can be prepared in a four step synthesis from 1,1,1,3-tetrachloropropane that is in turn produced by a reaction of ethylene and carbon tetrachloride.
In the preparation of the 1,1,1 t 3-te-tra-chloropropane, ethylene is reacted with carbon tetrachloride in the presence of both a source of metallic iron that is effective as an activator for the reaction, and a promoter for the reaction. According to a preferred embodiment, a reaction system is prepared comprising a liquid phase in contact with the source of metallic iron, the liquid phase comprising carbon tetrachloride and a promoter compatible therewith.
Preferably, the promoter comprises a phosphorus (V) compound containing a phosphoryl group such as, for example, an alkyl phosphate, alkyl phosphonate, phosphoryl chloride, or phosphorus pentoxide. Trialkyl phosphates such as , ~;~3~7

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triethyl phosphate and tributyl phosphate are most preferred. Other particular phosphorus (v) compounds which can be used as the promoter for the reaction include dimethyl methylphosphonate, die-thyl methylphos-phonate, phenyl ethylphosphonate, phenyl butyl phosphate,dimethyl phenyl phosphate, and the like. Alterna-tively, but less preferably, a trialkyl phosphite such as triethyl phosphite or tributyl phosphite may be used as the phos-phorus compound promoter for the reaction between ethylene and carbon te-trachloride. It has been found that higher productivity and yields are obtained with a trialkyl : phosphate promoter as compared to trialkyl phosphite.
Quality of the product is also generally~ better, and the reaction conditions less corrosive to process equipment.
A source of metallic iron effective as an activator for the reaction is necessary, along with the phosphorus promoter compound, to effect reaction of carbon tetrachloride with ethylene to produce the 1,1,1,3-te-trachloropropane with high selectivity, high yield and high productivity. Because the reaction is approximatel~ first order with respect to the contact surface between the liquid phase and the source of metallic iron, it is preferred that iron sources having relatively large surface areas be used. Various sources of metallic iron can be used in the reaction, with carbon steel and wrought iron being preferred. Carbon steels are particularly advantageous. Cast iron is also suitable. Useful forms of the iron source include , iron bars, rods, screens, filings, powder, sheets, wire, ;~ 30 tubes, steel wool, and the like.

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In order to maximize the selectivity o~ the reaction, it is further preferred that the liquid phase contain ferric chloride at the outset of the reaction.
This can be achieved by either adding ferric chloride to the system or generating it ln situ by heating the carbon tetrachloride in the presence of metallic iron and the promoter, preferably at about reaction temperature, prior to intxoduction of ethylene. Although the invention defined in the appended claims is not limited to a particular theory, it is believed that carbon tetra-chloride is split into a trichloromethyl free radical and a chloride ion ligand by a redox transfer with ferrous ion, thereby producing a ferric ion to which the ligand is attached. It is further believed that the metallic iron serves as a source of ferrous ions that participate in the postulated redox transfer with carbon tetrachloride, and that the promoter is instru-mental in the oxidation and dissolution of the metallic iron. Dissolution of metallic iron results in the formation of ferrous ions, either directly or by reduction of ferric ions in the liquid phase. Reaction of ethylene with the trichloromethyl radical produces a trichloropropyl radical that in turn condenses with the chloride ion ligand in a further redox transfer in which ferric ion is reduced to ferrous. Although ferric ion is thus produced in the course of the reaction by oxida-tion of ~errous ion, an initial concentration of ferric ion is useful in minimizing the formation of undesired by-products during the early stages of the reaction.
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Where a phosphorus (V) compound is used as the promoter, it is also preferred that the ferric chloride be substantially anhydrous and that the reaction system be maintained substantially free of water throughout the S reaction. In such systems, the presence of appreciable proportions of water significantly retards the reaction rate. However, where the promoter is a phosphite such as triethyl phosphite or tributyl phosphite, the presence of modest amounts of water is not disadvantageous. In fact, minor proportions of water, up to an amount stoichiometricly equivalent to the phosphite compound, may be useful in increasiny the reaction rate. This may be due to the conversion of phosphites to phosphates and/or phosphonates, and the attendant formation of HCl in the case of phosphate formation, by reaction with carbon tetrachloride.
In carrying out the first step of the synthesis, ethylene is introduced into the carbon tetrachloride li~uid phase containing the phosphorus compound, and preferably ferric chloride, in ~he presence of a source of metallic iron at a temperature of 50C to lSQC, preferably 70C to 130C. As noted, the ferric chloride may be initially added as such or generated ln situ by heating the CCl4-promoter-Fe metal sys-tem prior to introduction of ethylene. Ethylene pressure is not narrowly critical. Typically, ethylene can be intro-duced at a gauge pressure of between about l x 105 Pa and abou-t 14 x 105 Pa (about 1 and about 14 atmospheres).
It has fur-ther been found desirable to have a relatively high ratio of ferric iron concentration to ethylene partial pressure. However, it is also important to maintain a molar excess of phosphorus compound with ~3~57

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respect to ferric ion, since otherwis~ the reaction may stop. This is believed to result from the formation of a reaction product or 1:1 complex of phosphorus compound and iron ion. Although such reaction product or complex may still be active as a source of ferric ion for limiting the formation of n > 2 telomerization products, it appears to be lnactive as a promoter for initiating the reaction. Preferably, therefore, the reactor charge should initially contain between about 0.1 mole % and about 5 mole % of the phosphorous compound and between 0 and aDout 2 mole % ferric chloride based on carbon tetrachloride.
Progress of the reaction depends on maintaining a supply of both free phosphorus compound and metallic iron throughout the reac~ion period. In order to assure the continued availability of phosphorus compound and metallic iron, it is, therefore, necessary to control not only the initial phosphorus compound and ferric chloride content, but also the overall quantity of metallic iron avail~ble for dissolution and also the area of contact between the liquid phase and the source of metallic iron. Intensity of agitation also affects this balance.
For any given system, those skilled in the art may readily arrive at an appropriate combination of these parameters. Preferably the system is operated with vigorous agitation and contains a quantity of lron sufficient to provide for several batches (or several multiples of residence time in a continuous system) without significant varia-tion in surface area. This system both provides high productivity and facilitates maintenance of an effective supply of both phosphorus compound and metallic iron.

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The preparation of the starting materials can be according to the copending application of Scott S.
Woodard, Serial No. 45B,213.
In the process where the reaction of ethylene and carbon tetrachloride is catalyzed or promoted by a phosphorus (V) compound such as a trialkyl phosphate, in most instances the liquid product is substantially a single phase material containing a high proportion of 1,1,1,3-tetrachloropropane and can often be fed directly to the next step of the synthesis without further separation or purification. In the second step, the 1,1,1,3-tetrachloropropane is dehydrochlorinated by contacting it with a base, preEerably an aqueous caustic solution, in the presence of a phase transfer catalyst.
Preferably, the strength of the caustic solution is between about 15% and about 50~ by weight. Phase transfer catalysts useful in this reaction are known to the art. For example, various quaternary ammonium and qua-ternary phosphonium salts can be used to promote this dehydrochlorination step. The dehydrochlorination is preferably carried out by slowly adding the caustic solution to 1~1,1,3-tetrachloropropane containing the phase transfer catalyst while agitating the reaction mixture at a temperature oE 40C to 80C, preferably 50C to 75C. AEter addition of the caustic solution is complete, the mixture is stirred for an additional period at reaction temperature and then cooled. The aqueous phase is separated and discarded. The organic phase containing a mixture of 1,1,3- and 3,3,3-trichloro-propene may then be used directly in the next step of thesynthesis.

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In the next synthesis step, the trichloropro-pene mixture is chlorinated, preferably in the presence of ultraviolet light to produce 1,1,1,2,3-pentachloropro-pane. Chlorine gas may be introduced either above the liquid surface or through a dip plpe and sparger.
Chlorination temperature is not critical but may typically range from -10C to +80C, preferably 0C to 65C. Preferably the isomeric mixture of 1,1,3- and 3,3,3-trichloropropenes is chlorinated directly to produce 1,1,1,2,3-pentachloropropane. Alternatively, the trichloropropene isomers can be separated prior to chlorination of one or both of them, or the 3,3,3,-isomer component thereof first converted to the 1,1,3-isomer by contact with a Lewis acid allylic rearrange-ment catalyst. If FeC13 is used for the rearrangement reaction, it should be removed prior to chlorinationr as by distilling the isomerized material or extracting ~- the FeC13.
1,1,1,2,3-pentachloropropane is converted to an isomeric mixture of 2,3,3,3- and 1,l,Z,3-tetrachloropro-pene by dehydrochlorination with a base, preferably an agueous caustic solution, in -the presence of a phase transfer catalyst. Generally, the catalyst and caustic strengths used in this step may be approximately the same as those used in the dehydrochlorination of 1,1,1,3-tetrachloropropane. As in the earlier dehydrochlorina-tion step, caustic solution is added slowly to the penta-chloropropane containing the phase transfer catalyst.
However, the temperature used in this step may be somewhat higher than in the second step, i.e., in the range of 70C
to 110C, preferably 80C to 100C. After all caustic is added, the reaction mixture is cooled, the phases separated ,~

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and the aqueous phase discarded. The organic phase con-taining an isomeric mixture of 2,3,3,3- and 1,1,2,3-tetrachloropropene may be distilled prior to the isomeri-zation step.
To carry out the final step of the synthesis, the isomeric mixture of tetrachloropropenes is mixed with a Lewis acid allylic rearrangement catalyst which effects rearrangement of 2,3,3,3- to 1,1,2,3-tetrachloropropene.
However, if there is perceptible water in the isomeriza-tion mixture, as indicated, for example, by cloudiness or the presence of drops, or if a hydrated catalyst is used, the mixture is preferably subjected to azeotropic distilla-tion to remove residual water. Isomerization may proceed concomitantly with moisture removal, accelerating as the water content of the mixture declines.
Although other Lewis acid catalysts are known to be effective, it is particularly preferred that the isomerization reaction be carried out using substantially anhydrous ferric chloride as the catalyst.
It has been discovered that anhydrous ferric chloride catalyzes a very rapid allylic rearrangement of 2,3,3,3-tetrachloropropene to 1,1,2,3-tetrachloropropene without affecting the 1,1,2,3- isomer initially present or formed in the rearrangement reaction. Moreover, the catalytic proportion of ferric chloride needed for the step is quite low, for example, as low as 5 ppm. Higher concentrations promote more rapid reaction, but concen-trations above about 5% by weight do not serve a useful purpose. In fact, where the 1,1,2,3-tetrachloropropene : 30 is used for the preparation of triallate, relatively large proportions of FeCl3 in the 1,1,2,3-tetrachloropropene, ,.~

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for example 500 ppm or more, may lead to formation of ferric hydroxide which must be separated from the triallate. For this reason, FeC13 concentra-tion for catalyzing the rearrangement is preferably limited -to 5 ppm to ~00 ppm. Also, because tlle rearrangement is higllly exothermic, catalyst dosage and ini-tial reaction temperature should be adjus-ted to avoid an excessive temperature rise. Temperature increases of 80C or higher can be experienced. For -this reason, a diluent may also be desirable, for example, a heel of product from a prior batch.
I-t has further been found that the l,l,2,3-tetrachloropropene produced in the isomerization s-tep can be utilized directly wi-thout further purification in the synthesis of the llerbicide trialla-t~. Triallate is produced by reaction of 1,1,2,3-te-trachloroprope~e with diisopropylamille, car~onyl sul~ide and a base.
In the process of this invention, 1,1,1,2,3-pentachloropropane is converted directly to 1,1,2,3-tetrachloropropene by dehydrochlorination utilizingferric chloride as a dehydrochlorination cataly~t. In this embodiment of the invention, the 1,1,1,2,3-pentachloropropane is contacted with a catalytic proportion of ferric chloride. Preferably the dehydro-chlorination reaction is carried out at a temperature ofbetween about 70C and about 200C. The proportion oE
Eerric chloride utilized in the reaction is preferably between about 0.05% and about 2 r~ by weight oE the 1,1,1,2,3~pentachloropropane. When the dehydro-chlorination is carried out in this Eashion, hydrogenchloride gas is given oE~. This off gas may be either r ~.1 J

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absorbed in water or used directly in other operations.
Conversion to 1,1,2/3-tetrachloropropene is essentially ~uantitativeO Isomers of the desired product are either not formed or are immediately converted to the 1,1,2,3-isomer via an allylic rearrangement reaction ascatalyzed by the ferric chloride present.
Conversion of the 1,1,1,2,3-pentachloropropane is a simple operation realized at high productivity and yield; in the above process steps, each of the several steps of the processes can be run -to essentially complete conversion. However, some deterioration in yield is typically experienced at very high conversions in the dehydrochlorination of l,1,1,3-tetrachloropropane.
Typically, the incidence of by-product formation may increase to a significant level a-t conversions above 7~%.
In an alternative embodiment of the invention, therefore, conversion and/or by-product formation is monitored and addition of caustic solution terminated so as to limit the conversion to 80~ to 90~. The desired product can be separated from unreacted 1,1,1,3-tetrachloropane and the various by-products by fractional distillation following phase separation. Alternatively, the organics may be taken over by steam distillation without prior phase separation, and the takeover product fractionated.
Optionally~ the aqueous phase may be neutralized or acidified prior to steam distillation. In a still further embodiment, the trichloropropenes can be removed from the reaction as they are formed by fractional steam ; distillation. Any unreacted 1,1,1,3-tetrachloropropane can be recycled to the dehydrochlorination step.
The following examples illustrate the invention.

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Example 1 Carbon tetrachloride (273 g), triethyl phosphate (4.05 g), ferric chloride (1.03 g), and two mild steel rods having a total surface area of 26 cm2 were charged to a 300 ml Hastelloy C autoclave provided with an internal cooling coll. The autoclave was thereafter flushed twice with nitrogen and once with ethylene, pressurized with ethylene to about 4.1 x 105 Pa gauge ~4.1 atm gauge), and sealed. The mixture contained in the autoclave was stirred at 600 rpm and heated to 120C, at which temperature the pressure was observed to be approximately 8.3 x 105 Pa gauge (8.2 atm gauge). As a result cf the reaction of the carbon tetrachloride with the ethylene, the pressure in the clave dropped rapidly.
Within one minute of reaching 120C, the ethylene feed valve was reopened and the autoclave pressurized to about 9.8 x 105 Pa gauge (9.7 atm gauge) and maintained there for 150 minutes. The reactor was then cooled and vented. A product mixture (327 g) was obtained. No tars or solids were produced. However, a slight second phase did separate upon standing. The product mixture was analyzed and found to contain 95.1% by weight of 1,1,1,3-tetrachloropropane. Only 0.4% carbon tetra-chloride remained. The yield based on carbon tetra chloride initially present was 96.4%. The mild steel rods were weighed and it was determined that 0.54 g of iron had dissolved in the reaction mixture during the course of the reaction. A repeat of this reaction ; required 190 minutes to reach completion and the yield was 96.6%.

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Exam~le 2 Carbon tetrachloride (806 g), triethyl phosphite (8.8 g), acetonitrile (2.16 g), and ferric chloride hex-hydrate (1.~1 g) were charged to a one liter stainless steel autoclave equipped with a stirrer, cooling coil and condenser. The au-toclave was flushed wi-th nitrogen and then charged with ethylene to a gauge pressure of about 4.8 x 105 Pa gauge (4.8 atm gauge) while stirring the liquid charge. The liquid conten-ts of the autoclave were heated to 120C. As heating took place, the pressure rose to a peak of about 9.3 x 105 Pa gauge (9.2 atm gauge) and then began to drop as the temperature approached 120C.
When the temperature reachçd 120C, the autoclave was pressurized to about 9.8 x 105 Pa gauge (9.7 atm gauge) with ethylene and the reacting mixture maintained at - 120C and stirred for six hours at that ethylene pressure.
After six hours the reactor was cooled, then vented.
The liguid product collected from the autoclave weighed 952 g, of which 887 g was identified as 1,1,1,3-tetra-chloropropane (93.1% yield). No unreacted carbon tetra-chloride was detected in the product, indicating a 100%
conversion. Slight tar formation on the reactor cooling coils was noted.

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Example 3 Carbon tetrachloride (278 g), triethyl phos-phate (4.05 g) and two mild steel rods having a total surface area of 26 cm2 were charged to a 300 ml Hastelloy C autoclave. The autoclave was thereafter flushed twice with nitrogen, then once with ethylene, pressurized with ethylene to abou-t 3.4 x 105 Pa gauge (3.4 atm gauge), and sealed. The mixture contained in the autoclave was stirred and heated to 120C at which temperature the gauge pressure was observed to be approximately about 9.6 x 105 Pa gauge (9.S atm gauge). As a result o~
reaction of the carbon tetrachloride with ethylene, the pressure in the autoclave then dropped rapidly and, when the pressure dropped below about 6.9 x 105 Pa gauge (6.8 atm gauge), the ethylene feed valve was reopened, the autoclave repressurized to about 6.9 x 105 Pa gauge (6.8 atm gauge) and maintained at that pressure for a -total of four hours. The reactor was then cooled and vented. The product mixture (331 g) was analyzed and found to contain 93.5% by weight 1,1,1,3-tetrachloro-propane. Only 0.6% carbon tetrachloride remained. The yield based on the carbon tetrachloride initially present was 94.2%. The mild steel rods were weished and it was determined that 0.81 grams of iron had dissolved in the reacting mixture during the course of the reaction.

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Exam~le 4 Carbon tetrachloride (265 g), triethyl phosphate (4.18 g), and two mild steel rods having a total surface area of 26 cm were charged to the autoclave described in Example 1. The autoclave was thereafter flushed three times with nitrogen and sealed. The mixture contained in the autoclave was stirred at 600 rpm and heated to 120C, at which point the pressure was approximately 3.2 x 105 Pa gauge (3.2 atm gauge). After the mixture had been heated at 120C for 37 minutes, the ethylene feed valve was opened and the autoclave pressurized to 6.9 x 105 Pa gauge (6.8 atm gauge) and maintained at that pressure for 280 minutes. After 208 minutes o ethylene addition, 1.07 g of additional triethyl phosphate was charged to the autoclave, resultins in an increased reaction rate at that point, thereby effecting substantially complete reaction after a ~otal of 280 minutes of ethylene addition. the reactor was cooled and vented. A product mixture (317 g), similar in nature to ~hat in Example 1, was obtained. No tars or solids were produced. The ;; product mixture upon analysis was found to contain 94.3%
by weight 1,1,1,3-tetrachloropropane. Only 0.4% carbon tetrachloride remained. The yield based on carbon tetrachloride initially present was 96.2%. The mild steel rods were weighed and it was determined that 0.95 g o~ iron had dissolved in the reaction mixture during the course of the reaction.
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Example 5 1,1,1,3-tetrachloropropane (149 g; approximately 100% pure) and a tetraalkyl quaternary ammonium halide sold under the trade designation Aliquat 336 by General Mills (0.5~ g) were charged to a 500 ml ACE reactor having side indents and provided with a thermometer, mechanical stirrer and addition funnel. The addition funnel was charged with 50% sodium hydroxide solution (66.5 g) that had been diluted to approximately 140 ml (approximately 20% caustic). The mixture in the reactor was stirred and heated on a steam bath to 65C. When the temperature reached 65C, slow addition of caustic solution was commenced and this addition was continued over a period of 70 minutes. During caustic addition, the reaction temperature was maintained at 67 + 2C. When addition of caustic was complete, the reaction mixture was stirred for an additional 36 minutes at 67C. Stirring was then stopped and the mixture cooled. The aqueous phase was removed and the product organic phase determined to ~eigh 120 g, of which 55.1 g (51.8% yield) was 3,3,3 trichloro-propene, 35.6 g (42.8% yield) was 1,1,3-trichloropropene, and 16.3 g was unreacted 1,1,1,3-tetrachloropropane (89.1%) conversion).
The organic phase obtained from the reaction was distilled to provide a mixture of 3,3,3- and 1,3,3-trichloropropene of about 98.8% purity and containing a ratio of approximately 55 parts 3,3,3-isomer to 45 parts 1,1,3-isomer.
';

1~3~5~' -21- 09-21(2224)A

Example 6 A portion of the mixture of 3,3,3- and 1,1,3-trichloropropene prepared in Example 3 (66.0 g) was charged to a three-necX 100 ml round bottom flask e~lipped with a magnetic stir bar, an ultra violet lamp and two gas ports. The flask was then placed on an ice bath and the isomer mixture cooled to 0C.
While the contents of the flask were stirred and irradiated with ultra violet light, chlorine was fed into the flask via one of the gas ports at such rate : that a small but detectable amount exited the other gas port. Exit flow was detected by use o~ a gas bubbler. The chlorine input port was above the liquid surface. At intervals the reaction mixture was sampled to determine completeness of chlorination. After 36 minutes, all of both of the trichloropropene isomers were consumed, yielding 1,1,1,2,3-pentachloropropane in essentially 100% conversion. 98.7 g of organics were collected rom the flask of which 93.8 g (96.8%
; 20 yield) was 1,1,1,2,3-pentachloropropane.

Example 7 A 500 ml ACE reactor with side indents, equipped with a mechanical stirrer, addition ~unnel and thermometer, was charged with 1,1,1,2,3-pentachloro-propane (145 g; 97.4% pure) and Aliquat 336 (0.31 g).
The addition funnel was charged with a 50% caustic solution (55.2 g) which had been diluted to a volume of approximately 130 ml. The mixture contained in the reactox was s-tirred and heated via a steam bath to a . .
.~

~;~3~

-22- 09-21(2224)A

temperature of 90C and held a-t 90 ~ 2C throughout the subsequent reaction. When the contents of the reactor reached 90C, slow addition of caustic solution was commenced and continued over a period of two and one-half hours and then held for another one-half hour. The reaction mixture was cooled down, stirring terminated and the organic and aqueous phases separated. 118 g of organics was collected, of which 115 g (98.0% yield) was an isomer mixture of 2,3,3,3- and 1,1,2,3-tetrachloro-propene. No 1,1,1,2,3-pentachloropropane was detected in the collected organic phase, indicating that the conversion was 100%.

Example 8 The organic phase produced in accordance with Example 5, comprising an approximately 55j45 mixture 2,3,3,3- and 1,1,2,3-tetrachloropropene and containing no visible water ~no cloudiness or drops), was mixed with 0.17% by weight anhydrous ferric chloride. This mixture was heated at 103C for 15 minutes. Quantitative isomerization of 2,3,3,3- to 1,1,2,3-tetrachloropropene was achieved.

~., ", ..

~3~57 -23~ 09-21(2224)A

Exam~le 9 A one liter round bottom flask equipped with a condenser and collectox was charged with a mixture containing approximately a 45/55 ratio of 1,1,2,3-tetrachloropropene to 2,3,3,3-tetrachloropropene and 2.3 ml of a 1% aqueous ferric chloride solution. The mixture was heated to reflux, and the water azeotroped into the collector. All organics collected were returned to the flask. Within minutes of reaching re1ux and removal of the water, quantitative isomerization took place converting all of the 2,3,3,3-tetrachlo~opropene into 1,1,2,3-tetrachloropropene.

Example 10 A dry 100 ml round bottom flask equipped with a condenser and magnetic stir bar was charged with 94.5 g of 1,1,1,2,3-pentachloropropane (92.4% pure) and 0.26 g of ferric chloride. The mi~ture was heated and stirred at 164C for 7 hours. HCl gas was evolved during the reaction and was absorbed directly into water. After -- 20 cooling dcwn, 79.3 g of product mixture was obtained.
This was analyzed and found to contain 93.5% by weight 1,1,2,3-tetrachloropropene and 0.58% by weight starting material. This corresponds to conversion of 99.5% and an essentially quantitative yield.

.

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-24- 09-21(2224)A

As various changes could be made in the above methods without departing from the scope of the invention, it is intended that all matter contained in the above description shall be in-terpreted as illustrative and not in a limiting sense.

.

Claims

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

1. A process for producing 1,1,2,3-tetrachloropropene comprising contacting 1,1,1,2,3-pentachloropropane with a catalytic proportion of ferric chloride to effect dehydrochlorination of the 1,1,1,2,3-pentachloropropane to produce 1,1,2,3-tetrachloropropene.
2. A process as set forth in Claim 1, wherein 1,1,1,3-tetrachloropropane is dehydrochlorinated to produce a mixture of 1,1,3-trichloropropene and 3,3,3-trichloropropene, and preparation of Raid 1,1,1,2,3-pentachloropropane comprises chlorinating at least one of the trichloropropenes obtained by said dehydrochlorination of 1,1,1,3-tetrachloropropane.
3. A process as set forth in Claim 2, wherein 1,1,1,2,3-pentachloropropane is prepared by chlorinating said mixture of trichloropropenes.
process as set forth in Claim 2, wherein said mixture of 1,1,3-and 3,3,3-trichloropropenes is contacted with a catalyst, the 3,3,3-trichlorcpropene therein is isomerized to 1,1,3-trichloropropene, and 1,1,1,2,3-pentachloropropane is prepared by chlorinating the trichloropropene after the isomerization.
4. A process as set forth in Claim 2, wherein said mixture of trichloropropenes is distilled to separate the 1,1,3-trichloropropene from 3,3,3-trichloropropene, and the preparation of 1,1,1,2,3-pentachloropropane comprises chlorinating at least one of the trichloropropene fractions obtained by said distillation.

6. A process as set forth in Claim 2, wherein said 1,1,1,3-tetrachloropropane is dehydrochlorinated by contacting the 1,1,1,3-tetrachloropropane with a base in the presence of a phase transfer catalyst at a temperature of between about 40°C and about 80°C.
7. A process as set forth in Claim 2, wherein said 1,1,1,3-tetrachloropropane is prepared by reacting carbon tetrachloride and ethylene in the presence of an active source of metallic iron and a promoter for the reaction.
8. A process as set forth in Claim 7, wherein said promoter is selected from the group consisting of trialkyl phosphites and phosphorus (V) compounds containing a phosphoryl group.