US3420833A

US3420833A - Vapor phase production of polychlorinated compounds

Info

Publication number: US3420833A
Application number: US666474A
Authority: US
Inventors: William H Taplin
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1967-09-08
Filing date: 1967-09-08
Publication date: 1969-01-07
Anticipated expiration: 1986-01-07

Description

United States Patent 11 Claims ABSTRACT OF THE DISCLOSURE Aromatic, heterocyclic nitrogen compounds such as pyridines, quinolines, dipyridyls and quinoxalines are chlorinated to produce aromatic, heterocyclic nitrogen compounds having at least three chlorine substituents by introducing said nitrogen compound as a vapor in a substantially inert diluent vapor into a reaction zone with rapid turbulent mixing with at least four moles of chlorine per mole of nitrogen compound. The reaction zone is maintained at a temperature in the range of from at least 400 C. to about 700 C.

This application is a continuation-in-part of my copending application Ser. No. 321,283, filed Nov. 4, 1963, now abandoned.

Background of the invention Although chlorination of aromatic heterocyclic nitrogen compounds such as pyridine, picolines, lutidines, collidines, ethylpyridines and quinolines have been carried out in the vapor phase to obtain chlorinated derivatives thereof, the reported processes have yielded such a spectrum of products as to render the method impractical as production methods. Moreover, the known methods are almost always accompanied by extensive tar formation as well as formation of undesirable degradation products, inclusive of products in which the side chain and/ or nucleus :have been destroyed. This has been particularly true when it has :been sought to introduce three or more chlorine atoms into the molecule. Formation of tars and degradation products is an obvious economic waste. Moreover, the presence of such undesirable products renders purification and isolation of the desired product difiicult. Not infrequently, the presence of undesirable by-produ cts hinders the formation of the desired products in such manner, as to necessitate isolation of an intermediate chlorination product which may thereafter be subjected to further chlorination. The limitations of such methods are obvious. It is clearly seen that there is a need for a method for producing chlorination products of aromatic nitrogen heterocycles with substantially no tar formation and without significant degradation products formation.

It is an object of the present invention to provide methods for the chlorination of aromatic heterocyclic nitrogen compounds to produce chlorinated aromatic heterocyclic nitrogen compounds whereby formation of substantial quantities of degradative by-products may be avoided and whereby tar formation is substantially completely avoided. It is another object of the present invention to provide methods whereby 'highly chlorinated heterocyclic nitrogen compounds may be prepared substantially as a single or major component of a reaction product composition or may be prepared in such amounts as to make recovery of products practicable as a production method. It is a further object of the present invention to selec- "ice tively produce a polychlorinated product or product composition. It is a further object of the present invention to produce chlorinated heterocyclic nitrogen compounds containing three or more chlorine atoms in good yields and with substantially no tar formation. Another object is a method for the production of a polychlorinated alkylpyridine compound while controlling lysis of the alkyl side chain and avoiding tar formation to which alkylpyridines are particularly susceptible. Other objects will become apparent from the following specification and claims.

Summary of the invention According to the present invention, it has been discovered that aromatic heterocyclic nitrogen compounds may be chlorinated to produce polychlorinated aromatic heterocyclic nitrogen compounds substantially free of tarry by-products in a method whereby vapors of an appropriate heterocyclic nitrogen compound and appropriate diluent are rapidly and turbulently mixed with an excess of gaseous chlorine. It has further been discovered that three or more chlorine atoms may be introduced into a heterocyclic compound while avoiding the formation of degradative byproducts in a method which comprises vaporizing an aromatic heterocyclic nitrogen reactant, mixing the resulting vapor with a vapor of an inert diluent, and rapidly mixing the resulting vapor mixture with an excess of gaseous chlorine at elevated temperatures.

The expression aromatic heterocyclic nitrogen compound or simply heterocyclic nitrogen compound as employed herein means a heterocyclic nitrogen compound containing at least one six-membered ring containing only nitrogen and carbon atoms as ring-forming atoms and having aromatic properties by virtue of conjugated double bonds in said ring and said expression is further inclusive of such ring compounds bearing one or a plurality of neutral substituents on the carbon atoms of said ring compound. The heterocyclic nitrogen compounds having one or two nitrogen atoms in the aromatic ring are preferred. Suitable neutral substituents are alkyl or alkenyl groups of from one to three carbon atoms, trifluoromethyl groups and cyano groups. In general, when aromatic heterocyclic nitrogen compounds hearing such neutral substituents are employed it is preferred that any one ring in such compound should bear no more than three alkyl groups and no more than two alkenyl, trifiuoromethyl or cyano groups.

Representative aromatic heterocyclic nitrogen compounds include pyridines, pyridazines, quinolines, quinoxalines and the like. More particularly, suitable substrates for the chlorination process of the present invention include pyridine, lower alkyl pyridines such as isomeric picolines, isomeric ethylpyridines, isomeric lutidines and isomeric collidines, alkenylpyridines such as 2-, 3- or 4- vinylpyridine, cyanopyridines such as 2-, 3- or 4-cyanopyridine, 2,6-dicyanopyridine, 3,5-dicyanopyridine, quinoline, isoquinoline, alkyl quinolines such as quinaldine, lepidine or kryptidine, 2-, 3- or 4-cyanoquinoline, pyridazine, 2,2- dipyridyl, 4,4'-dipyridyl, quinoxaline and the like.

The diluents suitable for carrying out the process of the present invention are materials substantially inert to the action of chlorine under the reaction conditions and include nitrogen, carbon dioxide, perfluorinated hydrocarbons, perfluorochlorohydrocarbons and water. Chlorohydrocarbons such as chloroform can also be employed provided suflicient excess chlorine is supplied to convert the diluent to a perchlorohydrocarbon in the reaction zone. The preferred diluents are volatile perchlorinated hydrocarbons such as tetrachloroethylene, hexachlorobutadiene and carbon tetrachloride.

In carrying out the process of the present invention, mixed vapors of a heterocyclic nitrogen compound and an appropriate diluent are rapidly and turbulently mixed with an excess over the stoichiometric amount of gaseous chlorine during a brief contact time at temperatures of from at least 400 C. to about 700 C. It is critical and essential for the production of the desired products and avoidance of extensive degradation and tar formation that there be rapid and turbulent mixing of the reactants. It is further essential that the process be carried out in a manner that the heterocyclic compound be contacted with excess chlorine. Generally, there should be at least 30 percent excess of chlorine over the stoichiometric requirement for the desired polychlorinated heterocyclic nitrogen compound, that is, at least 4 moles of chlorine per mole of aromatic heterocyclic nitrogen compound in the reaction. The preferred ratios provide up to a 100 percent excess over the stoichiometric requirement of chlorine. it is among the advantages of the present process that when the reactants and diluents are mixed in the specified manner an exothermic, homogeneous reaction ensues. Thus, in an adiabatic reactor, the reaction proceeds to good yields of desired products without the use of heterogeneous or actinic catalysis or external heating.

Preferred conditions for carrying out the reaction are determined by the product or products desired. Thus, desirable ratios of chlorine to hererocyclic nitrogen compound, ratios of diluent to heterocyclic nitrogen compound, residence time and reaction temperature may depend on the reactant, i.e., whether pyridine, quinoline or alkylpyridine or the like and the degree of chlorination of the product and of the starting materials. Chlorine, itself, may be a neutral substituent on a partially chlorinated heterocyclic nitrogen compound and such partially chlorinated compounds may be further chlorinated in the present process. This embodiment of the invention is of particular importance from the standpoint of enabling recycle of incompletely chlorinated products from the process when the same is operated as a continuous process. Further, it has been found that by operating with large excesses of chlorine under the more stringent temperature conditions chlorinolysis of certain of the products may be accomplished. Thus, for example, pentachloropyridine can be produced by chlorinolysis of an alkyl group from an alkylpyridine or by chlorinolysis of the cyano group from a cyanopyridine. Thus the presence of partially chlorinated recycle product in the feed may somewhat reduce the degree of excess of chlorine required in the feed while the desire to accomplish chlorinolysis of substituents or to employ a chlorine-consuming diluent will generally require increase in the ratio of chlorine to starting materials.

In the chlorination of pyridine to produce polychloropyridines containing 3 or more chlorine substituents, the

chlorine to pyridine mole ratio may vary from about 4:1 to about :1. The higher chlorine to pyridine ratio is employed for the preparation of the more highly chlorinated product. Thus, when pyridine is to be chlorinated to produce pentachloropyridine as the major or sole product, the preferred chlorine to pyridine mole ratio is from about 8:1 to about 10:1. In the chlorination of alkylpyridines, the clorine to alkylpyridine ratio may vary from 4:1 to 18:1 or higher. In the chlorination of quinoline, pyridazine, isoquinoline, .dipyridyls and the like the ratio of chlorine to heterocyclic nitrogen compound may vary from 4:1 to 40:1 or higher.

In all the heterocyclic nitrogen compounds, suitable mole ratio of diluent to the heterocyclic nitrogen compound is from about 3:1 to about 54:1.

The nature of the product is also determined by the reaction temperature. The preferred temperature range depends not only on the heterocyclic nitrogen compound but also on the particular chlorinated product or products desired. When the heterocyclic nitrogen compound is pyridine, the temperature required to introduce three or more chlorine atoms in good yields is at least 400 C. and may be as high as about 700 C. The preferred range is from about 420 C. to 450 C. for the less highly chlorinated products and from about 500 C. to about 690 C. for the more highly chlorinated products. When the heterocyclic nitrogen is an alkylpyridine, the operable range is from 400 C. to about 600 C. with the preferred range being from 400 C. for the less highly chlorinated alkylpyridines to about 450 C. for the more highly chlorinated alkylpyridines when the chloroalkyl group is to be retained on the ring. However, for chlorinolysis of the alkyl groups temperatures of 500 C. or higher are preferred. When the heterocyclic nitrogen compound is quinoline, the operable range is from 400 C. to about 650 C. with the preferred range being from about 400 C. to about 600 C.

When operating with any particular heterocyclic nitrogen compound one or a few range-finding determinations suffice for choice of the proper temperature for obtaining desirable yields of a particular product. Thus, for example, with cyanopyridines as starting materials, reaction temperatures of from above 400 C. to around 500 C. yield minor proportions of trichloro and tetrachloro products with a major proportion of dichlorocyanopyridines. For obtaining good yields of trichlorocyanopyridines reaction temperatures of from about 540 C. to about 580 C. are preferred. Similarly to obtain gOOd yields of tetrachlorocyanopyridines reaction temperatures of from about 600 C. to about 630 C. are employed while operation with cy-anopyridines at temperatures above 650 C. leads to increasing chlorinolysis with formation of pentachloropyridine product. For polychlorination of compounds such as dip-yridyls, pyridazine and isoquinoline reaction temperatures of from about 550 C. to about 600 C. are preferred.

Although the exact residence time is not critical, the reactants should not be permitted to remain in contact for a prolonged period. The contact period or residence time depends on the temperature within the operable ranges of temperature for particular products. Thus, lowering the temperature ten degrees may double the permissible residence time but will ultimately be limited by the operable range for obtaining a particular product. Residence time generally will not exceed 5 to 6 minutes. The preferred time for contact is from about 5 to 35 seconds at temperatures up to about 600 C. At higher temperatures residence times of only 1 to 2 seconds suffice.

Operating pressures are not critical and may vary from subatmospheric to somewhat superatmospheric. Atmospheric pressure is satisfactory and is preferred.

In carrying out the reaction, the appropriate heterocyclic nitrogen compound and diluent are first introduced into an evaporator to produce the vaporized heterocyclic nitrogen compound in an inert diluent vapor. The evaporator is maintained at a temperature at which rapid vaporization occurs, usually in the range of from about C. to about 300 C., preferably from about C. to about 280 C. although somewhat higher temperatures may be required with high-boiling starting materials. Any vaporizing device may be employed as evaporator but a wiped film evaporator has been found convenient. For efficient operation it is necessary that the rate of introduction and/ or temperature of the evaporator be maintained so as to completely vaporize the reactant heterocyclic nitrogen compound and maintain the compound in the vaporized state. It has been noted that incomplete vaporization results in decreased yield of the desired chlorinated heterocyclic nitrogen compound. The mixed vapors which are produced are conducted from the evaporator and rapidly and turbulently mixed with the gaseous chlorine. Preferably, the mixing occurs at a point just prior to the point of entry to the reactor, and the resulting gaseous mixture is conducted at a rapid rate in a turbulent flow into the hot reactor where, in the vapor phase, a reaction takes place in the temperature range of from at least 400 C. to about 700 C. with the formation of the desired polychloroheterocyclic nitrogen compound. In one pre ferred embodiment the mixing of reactants is accomplished in a nozzle which injects the mixture into the reactor. Alternatively, the mixed vapors of heterocyclic nitrogen compound and diluent and the gaseous chlorine may be simultaneously but separately introduced into the reactor, but in such case, the gaseous chlorine must be jetted in at a point close to the point of introduction of the heterocyclic nitrogen compound in such manner to ensure very rapid mixing and turbulent flow of the reactants. The turbulence must be such as to provide a Reynolds number of at least 800. The preferred Reynolds number is about 2000. Generally, an inlet vapor velocity of about 40 to 100 feet per second is considered desirable. The reactor should be properly insulated to permit reaction to take place under adiabatic conditions. The vapors passing from the reactor are cooled or quenched to separate (a) a liquid mixture comprising polychlorinated heterocyclic nitrogen products, diluent and unreacted or partially reacted heterocyclic nitrogen compounds from (b) a gaseous mixture comprising chlorine and hydrogen chloride by-product. Depending on the product sought by the reaction, the liquid may be fractionally distilled to recover the desired products in substantially pure form of may be cooled to precipitate the product which is then recovered by filtration and the filtrate recycled to the evaporator preheater for further reaction. The gas mix ture may be scrubbed according to conventional procedures to separate chlorine from hydrogen chloride. The former may be dried and recycled while the latter may be recovered as hydrochloric acid. The product whether recovered by distillation or by precipitation and filtration may be further purified, if desired, by methods wellknown to the skilled in the art.

Any suitable reactor may be employed and, since the reaction is exothermic, strong heating is required only at the initiation of the reaction. Thereafter heat input is only necessary to compensate for heat loss to the environment. The inlets, outlets and interior surfaces of the reactor must be of materials such as are known to resist corrosion by chlorine and hydrogen chloride at high temperatures. Thus, for example, such surfaces may be lined with nickel, carbon, silica or glass. In practice, it has been found that thermally resistant, high-silica glass such as Vycor brand is satisfactory for small reactors. In large scale apparatus, it is convenient to employ a shell of nickel lined with fused silica or a suitable refractory such as carbon. To accomplish the essential rapid, turbulent mixing and introduction of the reactants into the reaction zone, the reactor may be fitted with a mixing nozzle, as described above, for introducing the reactants with substantially simultaneous mixing. Alternatively, the organic reactant plus diluent and the chlorine may be introduced into the reactor by separate but closely adjacent orifices adjusted so that the chlorine is jetted into the incoming stream of organic reactant plus diluent. In a further embodiment wherein the heterocyclic nitrogen compound, diluent and chlorine are introduced into the reactor with mixing immediately prior to such introduction, the mixing and introduction are carried out in a tube or the like of a diameter which is small in relation to the diameter of the reactor whereby turbulence at the entrance is achieved at relatively low Reynolds numbers in accordance with known principles. In a preferred form of apparatus the reactor proper is in the form of a cylinder having a length of 4 to 6 times the diameter. Conventional accessories, such as flowmeters on the inputs and condensors, cooling tubes or a quench tower for the exist gases, are employed.

In a preferred method for carrying out the process according to the present invention, a mixture of an appropriate heterocyclic nitrogen compound and perchlorohydrocarbon diluent is introduced into a wiped film evaporator where the reactant and diluent are vaporized, the vapors are rapidly mixed with gaseous chlorine and introduced into an adiabatic reactor at high turbulence whereupon a reaction takes place in the temperature range of from at least 400 C. to about 650 C. to produce the desired polychloroheterocyclic nitrogen compounds in the vaporous mixture, the mixture conducted from the reactor, condensed, and the product recovered from the liquid condensate by conventional procedures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples illustrate the invention but are not to be construed as limiting:

Example 1 Pyridine, at a rate of 109 grams (1.38 moles) per hour and carbon tetrachloride at a rate of 690 grams (4.48 moles) per hour were metered into a wiped film evaporator maintained at about 280 C. to vaporize the pyridine and carbon tetrachloride and the resulting mixed vapors conducted from the evaporator into the reactor while chlorine gas was metered into the gas flow at a rate of 910 grams (12.8 moles) per hour. The gases were rapidly mixed and passed through a reactor of 10 liter capacity where a reaction took place at a reactor temperature of about 560 C. and a residence time of about 21 seconds to produce a pentachloropyridine compound. The gaseous reaction mixture was recovered in a receiver which was fitted with a 2-inch jacketed sieve tray column at the exit end to condense and separate the liquid from gases. The liquid thus recovered was cooled to precipitate the highly chlorinated products and the remaining carbon tetrachloride solution of approximately percent carbon tetrachloride content and containing minor amounts of chlorinated pyridines and tetrachloroethylene formed from the carbon tetrachloride, was recycled as additional diluent at a rate of about 955 grams per hour and the chlorination process continued for 19.5 hours to obtain a pentachloropyridine product at a rate of 333 grams (1.31 moles) per hour and a tetrachloropyridine product at a rate of 8.5 grams (0.04 mole) per hour. 14.65 pounds of the two products were obtained. There was substantially no tar formation. The pentachloropyridine product was recovered from the reaction mixture by cooling to precipitate the product as a solid and thereafter filtering off the solid. Recrystallization of the product from carbon tetrachloride produced a pentachloropyridine product of 99 percent purity as determined by vapor phase chromatographic analysis through a column calibrated against authentic pentachloropyridine. The structure of the product was also confirmed by infrared spectral analysis.

Example 2 Pyridine was mixed with carbon tetrachloride and the mixture fed into an evaporator-preheater maintained at a temperature of about 280 C. to vaporize the mixture and to provide pyridine vapor at a rate of 0.60 mole per hour and carbon tetrachloride vapor at a rate of 22.3 moles per hour. The vaporized mixture was conducted from the evaporator, chlorine gas introduced into the mixed vapor stream at a rate of 6.5 moles per hour and the mixed gases immediately passed through a nozzle at a Reynolds number of about 2000 into a 5.35 liter adiabatic reactor whereupon a reaction took place at about 505 C. with the production of chlorinated pyridine compounds. The reaction was allowed to continue for two hours to obtain a chlorinated pyridine product composition as a yellow liquid containing 82.2 mole percent triand tetrachloropyridines. Vapor phase chromatographic analysis on the product composition showed it to contain 38.8 mole percent 2,4,6-trichloropyridine, 23.4 mole percent 2,3,4,6- tetrachloropyridine, 10 percent 2,3,6-trichloropyridine, 10 percent 2,3,5 ,6-tetrachloropyridine and minor proportions of pentachloropyridine and 2,6-dichloropyridine. In all vapor phase chromatographic (V.P.C.) analyses, the results were obtained through columns calibrated against authentic samples as standards.

7 Example 3 In a manner similar to that described in Example 2 with identical feed rates of pyridine, chlorine and carbon tetrachloride and identical reaction time but with the preheater temperature of about 260 C. and reactor temperature of about 525 C., an amber liquid product of chlorinated pyridines was obtained. The product contained 74.8 mole percent pentachloropyridine, 15.5 mole percent 2,3,4,6-tetrachloropyridine and minor proportions of 2,6-dichloropyridine, 2,4,6-trichloropyridine and 2,3,6- trichloropyridine as determined by V.P.C. analysis.

Example 4 In a manner similar to that described in Examples 2 and 3, but wherein the reactor temperature was about 480 C., a chlorinated pyridine product mixture was obtained as a light yellow liquid containing 71.2 mole percent triand tetrachloropyridines. The composition as determined by vapor phase chromatographic analysis contained 41.6 mole percent 2,4,6-trichloropyridine, 16.7 mole percent 2,3,6-trichloropyridine, 13.9 mole percent as a 1/3z2/3 mixture of 2,3,4,6 tetrachloropyridine and 2,3,5,6-tetrachloropyridine and 27.7 mole percent 2,6-dichloropyridine.

In a manner similar to that described in Examples 2 and 3, but wherein the reactor temperature was about 510520 C., a chlorinated pyridine product composition was obtained containing 67.7 mole percent triand tetrachloropyridines. The composition as determined by V.P.C. analysis contained 30.5 mole percent 2,3, 1,6-

tetrachloropyridine, 29.6 mole percent 2,4,6-trichloropyridine and 7.6 mole percent 2,3,6-trichloropyridine. In addition, there was 23.7 mole percent pentachloropyridine with the remainder being 2,6-dichloropyridine.

In a manner similar to that above described, good yields of triand tetrachloropyridines are obtained by turbulently contacting pyridine vapor diluted with water vapor with excess chlorine at temperatures of about 500 C.

Example 5 In a similar manner, (it-picoline was mixed with carbon tetrachloride and the mixture fed into an evaporatorpreheater maintained at a temperature of about 260 C. to vaporize the mixture and to provide a-picoline vapor at a rate of 0.38 mole per hour and carbon tetrachloride vapor at a rate of 20.7 moles per hour. The vapor mixture was conducted from the evaporator, chlorine gas introduced into the mixed vapor stream at a rate of 6. 5 moles per hour and the mixed gases passed through a nozzle at a Reynolds number greater than 300 into an adiabatic reactor whereupon a reaction took place therein at about 412 C. with the production of a polychloropicoline composition as a colorless liquid containing 96.7 mole percent trito pentachloropicolines with the tetrachloropicoline predominating. The composition as determined by V.P.C. analysis showed that the product contained 62.5 mole percent 2 chloro-6-(trichloromethyl) pyridine, 31.6 mole percent 2-(trichloromethyl)pyridine and 2.6 mole percent 4,6 dichloro-Z-(trichloromethyl) pyridine.

Example 6 In a similar manner, a-picoline was mixed with carbon tetrachloride and the mixture fed into an evaporatorpreheater maintained at a temperature of about 270 C. to vaporize the mixture and to provide a-picoline vapor at a rate of 0.50 mole per hour and carbon tetrachloride vapor at a rate of 17.6 moles per hour. The vapor mixture was conducted from the evaporator, chlorine gas introduced into the vapor stream at a rate of 2.0 moles per hour and the mixed gases immediately introduced into the reactor through a nozzle at high turbulence into an adiabatic reactor whereupon a reaction took place therein at about 480 C. with the production of a polychloropicoline composition containing 87.4 mole percent trito pentachloropicolines with the tetrachloropicoline predominating. The composition was determined by V.P.C. analysis as containing 60.5 mole percent 2-chloro- 6 (trichloromethyl)pyridine, 20.0 mole percent 2,4-dichloro-6-(trichloromethyl)pyridine and 6.9 mole percent 2,5-dichloro-6-(trichloromethyl)pyridine.

Example 7 In a manner similar to that described in Examples 5 and 6 but wherein the chlorine to a-picoline ratio was 13:1, the carbon tetrachloride to a-picoline ratio was about 42:1 and the reactor temperature was 400 C., a polychloropicoline product composition was obtained as a light yellow liquid containing 73.1 mole percent trito pentrachloropicolines with the trichloropicoline predominating. The composition as determined by V.P.C. analysis contained 38.2 mole percent Z-(trichloromethyl) pyridine, 35.6 mole percent 2-chloro-6-(trichloromethyl) pyridine and 1.3 mole percent 2,4-dichloro-6-(trichloromethyl)pyridine.

In a manner similar to that described in Examples 5 and 6 but wherein the chlorine to picoline ratio was 9:1, the carbon tetrachloride to picoline ratio was about 35:] and the reactor temperature was about 480 C., a polychloropicoline product composition was obtained as a light yellow liquid containing 78.7 mole percent trito hexachloropicolines with the pentachloropicoline predominating. The composition as determined by V.P.C. analysis contained 37.0 mole percent 2,4-dichloro-6-(trichloromethyl) pyridine, 27.5 mole percent 2 chloro-6- (trichloromethyl) pyridine, 9.5 mole percent 2,5-dichloro- 6-(trichloromethyl)pyridine and 4.7 mole percent 2,3,5- trichloro-6-(trichloromethyl)pyridine.

Example 8 In a manner similar to that previously described, picoline was mixed with carbon tetrachloride and the mixture fed into an evaporator-preheater maintained at a temperature of about 200 C. to vaporize the mixture and to provide 'y-picoline vapor at a rate of about 0.5 mole per hour and carbon tetrachloride vapor at a rate of about 17.5 mole per hour. The vaporized mixture was conducted from the evaporator, chlorine gas introduced into the vapor stream at a rate of about 2 moles per hour in a nozzle which introduced the mixed gases into the reactor at high turbulence whereupon a reaction took place therein at about 480 C. The reaction was allowed to continue for about 5.5 hours to obtain a polychloro-vpicoline product composition containing 76.0 mole percent 2,6-dichloro-4-(trichloromethyl)pyridine as determined by V.P.C. analysis. The 2,6-dichloro-4-(trichloromethyl)pyridine product was recovered from the reaction mixture by vaporizing oh? the diluent and cooling to precipitate the product as a crystalline solid. The solid was filtered and recrystallized from ethyl alcohol to obtain a purified 2,6-dichloro-4-(trichloromethyl)pyridine product. The melting point of 2,6-dichloro-4-(trichloromethyl)pyridine is 56-58 C.

Example 9 In a manner similar to that previously described, apicoline vapor diluted with Water vapor in a ratio of 5.95 moles of a-picoline to 155 moles of water and excess chlorine were rapidly mixed and introduced at high turbulence into a reactor maintained at 410 C. over a period of 2 hours and 25 minutes whereupon a reaction took place with the production of 1020 grams of polychloropicoline composition containing 88.7 mole percent trito tetrachloropicolines. The product as determined by V.P.C. analysis contained 52.0 mole percent 2-chloro- 6-(trichloromethyl)pyridine, 28 mole percent Z-(trichloromethyl)pyridine and 8.7 mole percent trichloropicoline.

9 Example 10 In a manner similar to that previously described, quinoline was mixed with carbon tetrachloride and the mixture fed into an evaporator-preheater maintained at a temperature of about 250 C. to vaporize the mixture and to provide quinoline vapor at a rate of about 118 grams (0.91 mole) per hour and carbon tetrachloride vapor at a rate of about 1810 grams (12 moles) per hour. The vaporized mixture was conducted from the evaporator, chlorine gas introduced into the vapor stream at a rate of about 11.2 moles per hour and the mixed gases introduced into a reactor at high turbulence whereupon a reaction took place at about 440 C. The reaction was allowed to continue for about 2.2 hours to obtain a polychloroquinoline product composition at a rate of 282 grams per hour containing 86.9 mole percent tri-, tetraand pentachloroquinolines as determined by V.P.C. and elemental analyses. The remainder of the product was dichloroquinoline. The mixture was fractionally distilled to recover a trichloroquinoline fraction of 90 percent trichloroquinolines by V.P.C. analysis boiling from 130 to 135 C. at 0.7 millimeter of mercury pressure, a tetrachloroquinoline fraction of 90 percent tetrachloroquinolines by V.P.C. analysis boiling from 146 to 150 C. at 0.7 millimeter of mercury pressure and a pentachloroquinoline fraction of 98 percent pentachloroquinolines by V.P.C. analysis boiling from 180 to 184 C. at 0.7 millimeter of mercury pressure.

Example 11 In a reaction carried out in a manner similar to that described in Example 10, good yields of tri-, tetraand pentachloroquinoline are obtained by turbulently contacting quinoline vapor diluted with tetrachloroethylene vapor with excess chlorine at temperatures of about 450 C.

In a similar reaction, good yields of tri-, tetraand pentachloroquinolines are obtained when the tetrachloroethylene vapor is substituted with water vapor.

Example 12 In a manner similar to that previously described, 154 grams (1.25 moles) of 2-ethylpyridine was mixed with 1186 grams (7.7 moles) of carbon tetrachloride and the mixture fed into an evaporator-preheater maintained at a temperature of about 250 C. to vaporize the mixture and to provide 2-ethylpyridine vapor and carbon tetrachloride vapor. The vaporized mixture was conducted from the evaporator, 6.2 moles of chlorine gas introduced into the vapor stream and the mixed gases introduced into a reactor at high turbulence wheerupon a reaction took place at about 420 C. The reaction was continued for 33 minutes to obtain 205 grams of a polychloro-2-ethylpyridine product composition, containing 37.0 mole percent of trichloro-2-ethylpyridines and 63.0 mole percent of tetrachloro-Z-ethylpyridines.

Example 13 In a manner similar to that previously described, 2,4- lutidine is mixed with tetrachloroethylene and the mixture fed into an evaporator-preheater maintained at a temperature of about 200 C. to vaporize the mixture and to provide 2,4-lutidine vapor at a rate of about 0.5 mole per hour and tetrachloroethylene vapor at a rate of about 18 moles per hour. The vaporized mixture is conducted from the evaporator, chlorine gas introduced into the vapor stream at a rate of about 3 moles per hour and the mixed gases introduced into a reactor at high turbulence whereupon a reaction takes place therein at about 450 C. to produce a polychlorolutidine composition.

Example 14 In a similar manner to that previously described, 7- collidine is mixed with tetrachloroethylene and the mixture fed to an evaporator-preheated maintained at a temperature of about 200 C. to vaporize the mixture and to provide 'y-collidine vapor at the rate of about 0.9 mole per hour and tetrachloroethylene at a rate of about 18 moles per hour. The vaporized mixture is conducted from the evaporator, chlorine gas introduced into the vapor stream at a rate of about 4.5 moles per hour and the mixed gases immediately introduced into an adiabatic reactor at high turbulence whereupon a reaction takes place therein at about 450 C. to produce a polychloro-ycollidine composition.

Example 15 A cylinder of Vycor high-silica glass of 3.5 inch diameter and about 18 inches in length was tapered to inlet and outlet tubes and fitted with electrical heating coils and efiicient insulation to serve as a reactor having a capacity of about 2.2 liters. The outlet was connected to a coolable collection vessel and the latter was vented through a reflux condenser to an acid-gas recovery system. The inlet tube ended in a nozzle projecting about 1 inch into the reactor and having an opening into the reactor 2.5 millimeters in diameter. Inside the nozzle was a smaller concentric tube for chlorine introduction ending 0.5 inch before said nozzle opening. The upstream end of the inlet tube connected to an electrically heated vaporizer-preheater tube for introduction of the organic reactant and diluent.

A solution consisting of 5 percent by weight of 4,4- dipyridyl, 34 percent by weight of chloroform and 61 percent by weight of carbon tetrachloride was metered into the vaporiZer-preheater at a rate of about 3.2 grams per minute while the vaporizer was heated so that the resulting vapor mixture passed to the inlet nozzle at a temperature of about 370 C. In the nozzle the dipyridyl and diluent vapor was rapidly mixed with chlorine as the reactant mixture was forced through the nozzle into the reactor at a velocity of about 44 feet per second. The chlorine was introduced at a rate to provide 26 moles of chlorine per mole of dipyridyl in the reaction mixture plus sufiicient excess to convert the chloroform in the feed to carbon tetrachloride. The reaction was carried out at a reactor temperature of 555 C. with a residence time in the reactor of about 30 seconds. The condensible product was collected in the collection vessel externally cooled with ice. The crude product was recrystallized from carbon tetrachloride to obtain the octachloro-4,4-dipyridyl product as a crystalline solid melting at 221-222 C. The structure of the product was confirmed by elemental analysis and mass spectrometry. A vapor phase chromatogram of the crude product showed that said product contained 98 mole percent of said octachloro compound.

Example 16 Using the apparatus and general procedure of Example 15, a solution of 7.5 percent by weight of 2,2'-dipyridyl in carbon tetrachloride was passed through the vaporizer at temperatures of from 275 to 290 C. The resulting vapor mixture was mixed in the nozzle with 41 moles of chlorine per mole of dipyridyl and passed into the reactor at a velocity of about 60 feet per second. The reaction was carried out at a reactor temperature of 555 C. with a residence time of 22 seconds to produce a crude product containing about 93 mole percent of octachloro-2,2-dipyridyl and about 4 mole percent of pentachloropyridine (by V.P.C.). The crude product was recrystallized from a mixture of benzene and thanol to obtain octachloro-2,2-dipyridy1 as a crystalline solid melting at 187 C. The identity of the major product was confirmed by elemental analysis and mass spectrometry.

Example 17 The apparatus and general procedure of Example 15 were employed with the following variables:

Feed: Solution of 5 percent by weight of 2,5-dicyanopyridine in chloroform.

Vaporizer temperature: About 380 C.

Molar ratio of C1 About 14.4 moles per mole of dicyanopyridine plus suflicient to convert chloroform to carbon tetrachloride.

Nozzle velocity: 46 feet per second.

Reactor temperature: 600 C.

Residence time: 29.2 seconds.

The crude product was found to contain 96 mole percent of 3,4,6-trichloro-2,S-dicyanopyridine. The latter, after recrystallization from a mixture of benzene and carbon tetrachloride, was found to melt at 199 -200 C.

Example 18 In similar fashion to Example 15, using a feed of percent quinoline in carbon tetrachloride, an input of 23 moles of chlorine per mole of quinoline, reactor temperature of 610 C. and residence time of about 24 seconds, there was obtained a high yield of heptachloroquinoline.

Similarly 2-cyanoquinoline in carbon tetrachloride was reacted with a large excess of chlorine to produce hexachloro-Z-cyanoquinoline.

Example 19 Using a Vycor glass reactor designed essentially like that of Example but having a reaction volume of 10 liters, 1.11 gram-moles of 3-cyanopyridine per hour was continuously fed into the vaporizer in the form of a 10 percent by weight solution in carbon tetrachloride. At the entrance nozzle the 3-cyanopyridine and CCL, vapors were rapidly and turbulently mixed with an input of chlorine at the rate of 13-gram-moles per hour and the resulting mixture injected into the reactor maintained at a temperature of 480 C. The reaction product was quenched in a cold collection vessel and a solid was observed to crystallize from the product condensate. The latter condensate was filtered and the solid product obtained as a filter cake was found to be substantially pure tetrachloro-3-cyanopyridine melting at 148149 C. The identity of this tetrachloro compound was confirmed by V.P.C. and by infra-red spectrography. It was obtained in a yield of 79 percent of theoretical.

Example Using a reactor designed similarly to that of Example 15 but having a volume of 5 liters, over a period of two hours 6.2 moles of Z-cyanopyridine dissolved in 72.1 moles of CCl.; was fed to the vaporizer maintained at a temperature of 180 C. and the resulting vapors rapidly and turbulently mixed with 26.3 moles of chlorine. The resulting mixture was injected immediately as formed into the reactor maintained at a temperature of 630 C. At this temperature, additional chlorine is produced in the reactor in the amount of over one mole of chlorine per 5 moles of carbon tetrachloride in the feed by the condensation of carbon tetrachloride with itself to produce tetrachloroethylene. The exiting vapors from the reactor were condensed and collected and the resulting product separated by conventional procedures such as evaporation of solvents and crystallization. The product was found by analysis to contain 0.19 mole of trichloro-Z-cyanopyridines, 4.86 moles of tetrachloro-Z- cyanopyridine and 0.88 mole of pentachloropyridine.

In similar fashion, one molar proportion of 3-chloropyridazine is vaporized with 14 molar proportions of CCl.;, the resulting mixture injected with 22 molar proportions of chlorine into the reactor at 600 C. for a residence time of about 11 seconds to produce tetrachloropyridazine.

Example 21 Using a reactor similar in design to that of Example 15 but having a volume of 1.35 liters, a solution of 10 percent by weight of 2-vinylpyridine in carbon tetrachloride was fed at the rate of about 3 grams per minute into a vaporizer maintained at a temperature of about 180 C. The resulting vapors were rapidly and turbulently mixed with chlorine introduced at the rate of 4.65 grams per minute and the resulting mixture immediately injected into the reactor maintained at a temperature of 595 C. for a residence time of 13.2 seconds. The exiting vapors were quenched and collected. V.P.C. analysis showed the product to contain 3.2 mole percent of nonachloro-2-ethylpyridine, 10.3 mole percent of pentachloropyridine and 83.6 mole percent of heptachloro-2- vinylpyridine. The identity of the products was confirmed by infra-red and mass spectroscopy and by elemental analysis.

Example 22 Using the apparatus and general procedure of Example 15 with a feed consisting of a 10 percent by weight solution of 2-chloro-6-trifluoromethylpyridine in carbon tetrachloride and employing 18 moles of chlorine per mole of pyridine compound, the chlorination was carried out at a temperature of 540 C. and a residence time of 16 seconds to produce a product containing by V.P.C. analysis about 55 mole percent of tetrachloro-2- trifiuoromethylpyridine and 15 mole percent of pentachloropyridine with the remainder consisting of chloro- Z-trifiuoromethylpyridines of lesser degrees of chlorination.

When this chlorination was repeated at reactor temperatures of 580 C. or higher, increased proportions of pentachloropyridine were obtained.

A chlorination was similarly carried out with a 10 percent by weight solution of isoquinoline in CCl as feed and employing 35 moles of chlorine per mole of isoquinoline, a reaction temperature of 600 C. and residence time of 25 seconds to produce a polychlorinated isoquinoline product containing 45 mole percent of heptachloroisoquinoline. In exactly similar fashion, quinoxaline is chlorinated to produce a substantial proportion of hexachloroquinoxaline.

Example 23 Pyridine was chlorinated in a commercial reactor having a nickel shell lined with carbon brick and equipped with external heating coils and insulation for operation as a high-temperature adiabatic reactor. Mixed vapors having a composition of from 12 to 13.5 pounds of tetrachloroethylene to 1 pound of pyridine were preheated and rapidly and turbulently mixed with chlorine in the proportions of 9 to 9.5 moles of chlorine per mole of pyridine. The mixing was accomplished in a nozzle and the resulting mixture injected at high velocity into the reactor for a residence time of about 2 seconds at a reaction temperature of 685-6 C. The exiting gases were quenched in a refluxing column with tetrachloroethylene. The crude product was Worked up by evaporation of solvent, crystallization and filtration to obtain the product as a crystalline solid consisting of pentachloropyridine of 98 percent purity and in a yield of 94 percent of theoretical.

The products of the present invention have numerous uses. Many of the polychloro-heterocyclic nitrogen compounds are useful as intermediates for the preparation of other chlorinated heterocyclic nitrogen compounds such as chloropyridyl sulfones useful as paint preservatives. Also, for example, heterocyclic nitrogen compounds which have chlorine substituted on the nucleus are useful as intermediates for the preparation of halohydroxyheterocyclic nitrogen compounds. For the preparation of such compounds, the chloro-heterocyclic nitrogen compound may be heated with 10 percent aqueous caustic at temperatures of from about to about C. for about 2 to 3 hours. 2,3,5-trichloro-4-pyridinol prepared from 2,3,4,5-tetrachloropyridine is an excellent herbicide. The chloro-heterocyclic nitrogen compounds which have alkyl side chains which have been chlorinated by the process of the present invention are useful as intermediates in the preparation of carbonyl compounds by hydrolysis of the chlorine in the side chain. Thus, for example, chlorination products having the trichloromethyl group may be heated with strong acid in the temperature range of from about 80 to about 180 C. for a period of from about 0.25 to 2 hours to obtain heterocyclic acid compounds such as chloropicolinic acids, pyridine-dicarboxylic acids, quinolinic acids, chloroquinolinic acids, etc.

Certain of the products obtained by the process of the present invention are useful for the control of undesirable plants and weed seeds. Thus, in representative operations,

aqueous compositions containing one of 2,3,5,6-tetrachloropyridine and pentachloropyridine give good controls of vegetation such as wild oats when applied at a dosage of 50 pounds per acre to soil planted therewith.

Certain of the compounds are useful for the control of soil-dwelling pests. Thus, 2,4-dichloro-6-(trichloromethyl) pyridine gives complete controls of soil-dwelling fungi when the organisms are exposed to grow media containing said compound at a concentration of 1000 parts by weight per million parts by weight of medium.

The cyano-polyhalopyridines are fungicides and may be distributed in soil to control damping-off organisms. Further uses of polyalocyanopyriclines are shown in U.S. Patent 3,325,503. The polyhaloquinolines may be converted to their N-oxides which are useful as fruit fly repellants. Tetrachloro-Z-trifiuoromethylpyridinb has been found to have anthelmintic properties useful for the control of intestinal parasites. Perchloroquinoxaline and 3- cyano-perchloroquinoline have been found useful as fungicides while perchloro-4,4'-dipyridyl is an effective herbicide. Others of the polychlorinated heterocyclic nitrogen compounds are useful as nitrification inhibitors in soil.

A cursory and by no means exhaustive examination of the prior art shows numerous examples of knowledge of how to use products of the disclosed processes.

Burckhalter et al.: 70 J. Am. Chem. Soc. 1363-73 (1948).Polychloroquinolines, as for example tetrachloroquinolines are reacted with 4-acetamido-ot-diethyl- 'amino-o-cresol to produce antimalarial agents.

Hopff et al.: 47 Makromol. Chem. 93113 (1961).- Pyridine-dicarboxylic acids reacted with hexamethylenediamine gave polyamides suitable for use as synthetic fibers.

US. Patent 2,940,974, June 14, 1960.-Trichloroquinolines reacted with alkylenediamines gave derivatives having hypotensive activity.

French Patent 1,170,743, published January 16, 1959.- Polychloro-pyridines, -picolines, -quinolines, -isoquinolines, -pyrimidines, -pyridazines, -quinazolines, and -quinoxalines are used as plant growth control agents.

British Patent 927,974, published June 6, 1963.-- Polychlorinated heterocyclic compounds such as tetrachloroquinazoline are employed to make dyestuif intermediates.

German Patent 942,507, May 3, 1956.Polychloroquinazolines, for example trichloroquinazoline, are employed for treating freshly dyed fabrics to increase dyefastness.

US. Patent 3,044,930, July 17, 1962.N-oxides, prepared by known methods from polychloropyridines, -quinolines and isoquinolines, are employed to repel birds and rodents.

US. Patent 2,679,453, May 25, 1954.A variety of trichloromethyl-substituted pyridines are employed to control the growth of vegetation.

South African Patent 411/61, granted Oct. 11, 1961.- A variety of chlorinated trichloromethyl pyridines are employed to inhibit the nitrification of ammonium nitrogen in soil.

Belgian Patent 624,800, granted May 14, 1963.-Polychloro-methyl-pyridines are shown to be useful as nitrification inhibitors in soil, as herbicides, as nematocides, as insecticides and as fungicides.

Belgian Patent 502,840, granted Feb. 15, 1963.Polychloro-methylpyridines are reacted with ammonia or amines to produce 4-amino-polychloro-methylpyridines shown to be useful as herbicides and pesticides active against a variety of named pests.

Belgian Patent 502,841, granted Feb. 15, l963.- Amino compounds of Belgian 502,840 are reacted with strong acid to produce corresponding amino-chloropicolinic acids having outstanding herbicidal activity.

I claim:

1. A process for the production of polychlorinated aromatic heterocyclic nitrogen compounds having at least three chlorine substituents which comprises introducing into a reaction Zone with rapid, turbulent mixing, a vaporized aromatic heterocyclic nitrogen compound in a substantially inert diluent vapor and at least four molar proportions of chlorine per molar proportion of nitrogen compound while said reaction zone is maintained at a temperature in the range of from at least 400 C. to about 700 C.

2. A process is accordance with claim 1 wherein the diluent is :a perchlorinated hydrocarbon.

3. A process in accordance with claim 1 wherein the aromatic heterocyclic nitrogen compound is pyridine.

4. A process in accordance with claim 1 wherein the aromatic heterocyclic nitrogen compound is an alkylpyridine.

5. A process in accordance with claim 1 wherein the aromatic heterocyclic compound is a monocyanopyridine or a dicyanopyridine.

6. A process in accordance with claim 1 wherein the aromatic heterocyclic nitrogen compound is quinoline.

7. A process in accordance with claim 1 wherein the diluent is carbon tetrachloride or tetrachloroethylene.

8. A process according to claim 1 wherein the aromatic heterocyclic nitrogen compound is pyridine, alkylpyridine,

alkenylpyridine or cyanopyridine and the diluent is carbon tetrachloride or tetrachloroethylene.

9. A process according to claim 1 wherein the aromatic heterocyclic nitrogen compound is pyridine and the diluent is carbon tetrachloride.

10. A process according to claim 1 wherein the aromatic heterocyclic nitrogen compound is pyridine and the diluent is tetrachloroethylene.

11. A process according to claim 1 wherein the aromatic heterocyclic compound is cyanopyridine and the diluent is carbon tetrachloride.

References Cited UNITED STATES PATENTS 3,153,044 10/ 1964 Zaslowsky 260290 3,251,848 5/1966 Taplin 26029O 3,285,925 10/1966 Johnston et a1. 260294.9 3,317,549 5/1967 Johnston 260294.9 3,325,503 6/1967 Bimber 260-2949 ALTON D. ROLLINS, Primary Examiner.

D. DAUS, Assistant Examiner.

US. 01. X.R. 260-290, 294.9, 250, 296, 674, 295, 999, 233; 71-94