GB1593169A - Causticfree process for the production of monochloro-di(monalkylamino)-s-triazines - Google Patents

Description

(54) A CAUSTIC-FREE PROCESS FOR THE PRODUCTION OF MONOCHLORO DI(MONOALKYLAMINO)-S-TRIAZINES (71) We, CIBA-GEIGY AG, a Swiss body corporate, of Basle, Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a new and improved procedure for the preparation of monochloro-di(monoalkylamino)-s-triazines of known herbicidal activity. The monochloro-diamino-s-triazines are obtained by the present procedure not only in high yield and excellent product quality, but also without giving rise to problems in effluent treatment and disposal. The term "alkyl" in the context of the monoalkylamines and monoalkylamino substituents mentioned herein means unsubstituted or alkoxy-substituted alkyl.

The herbicidal activity of various monochloro-diamino-s-triazines has been described, for example, in Gysin et al. U.S. Patent No. 2,891,855. One such monochloro-diamino-s-triazine, which is commercially useful as a herbicide, is 2 chloro-4-ethylamino-6-isopropylamino-s-triazine. This compound is commercially available as an atrazine herbicide. The aforesaid 2-chloro-4-ethylamino-6isopropylamino-s-triazine can, as described in the Gysin et al. patent referred to above, be prepared from cyanuric chloride and the corresponding organic amines.

The synthesis ordinarily proceeds via the formation of the 2,4-dichloro-6isopropylamino-s-triazine intermediate compound in accordance with the following reaction:

The 2,4-dichloro-6-isopropylamino-s-triazine compound is thereafter converted to the active compound, i.e. 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, referred to as atrazine, by reaction with monoethylamine, as follows:

The first step (equation A above) is accompanied by a number of undesirable side reactions, which may for example involve the hydrolysis of some of the chloro amino-s-triazines or the formation of various by-products, such as 2-chloro-4,6-bisisopropylamino-s-triazine. The undesired formation of the last mentioned material, where the preparation of the atrazine product is concerned, may proceed in accordance with the following reaction scheme:

In the preparation of 2-chloro-4,6-diamino-s-triazines and, by way of illustration, of the atrazine herbicide, i.e., 2-chloro-4-ethylamino-6isopropylamino-s-triazine, it will be appreciated that it is desirable to minimize the co-production of the by-product illustrated in equation C) and of other by-products, thereby avoiding difficulties in isolating the desired atrazine product when said product is produced on a large scale. It is also highly desirable to produce the 2chloro-4,6-diamino-s-triazines in high yield and purity without creating problems in effluent treatment and disposal because of the aqueous NaCI and other triazine byproducts contained in the aqueous effluent of the above described process of manufacture.

U.S. Patent No. 3,328,399 discloses a process for preparing amino-s-triazines without neutralizing the HCI formed in the reaction. However, this patent discloses only a method involving reacting cyanuric chloride with secondary amines in an anhydrous system and the HCI formed is distilled off from the reaction mixture.

Also, U.S. Patent No. 3,586,679 discloses a process for the production of dichloro-monoamino-s-triazines in an anhydrous medium.

In the present invention, monochloro-di-(monoalkylamino)-s-triazines are produced in high yield and purity, with a reduced consumption of energy and reactants, by a process which comprises: (I) a first stage, of reacting at a temperature of from 90 to 200"C and normal or elevated pressure, cyanuric chloride and a monoalkylamine hydrochloride in substantially stoichiometric amounts to form 2,4 dichloro-6-monoalkylamino-s-triazine and two moles of HCI gas, (II) a second stage, of reacting the solution obtained from stage (I) after cooling, at a temperature of from 40 to 100"C and lower than employed in stage (I), and at normal pressure, with a 100% or greater molar excess of a monoalkylamine, to form a monochloro-di-(monoalkylamino)-s triazine and monoalkylamine hydrochloride, in which the term "alkyl" means unsubstituted alkyl or alkoxy-substituted alkyl.

The first reaction stage (I) can be illustrated as follows:

fl Cl C C N N N + 2HCl (gas) I II II C1-C C-C1 + alkyl-NH3.ClCl- C-NH-alkyl N Examples of preferred monoalkylamines are: methylamine, ethylamine, npropylamine, isopropylamine 1,2-dimethyl-n-propylamine, 1 -methyl-2-methoxy- ethylamine. Stage I is performed at a reaction temperature between 90 and 2000 C, preferably between 120 and 1500C, at normal or elevated pressure, e.g. I to 10 atmospheres, and preferably in an inert solvent or diluent, which will ordinarily be organic.

Suitable solvent or diluents for this process stage are aromatic hydrocarbons, for example, toluene, o-xylene, m-xylene, p-xylene or a mixture thereof, or chlorinated aliphatic or aromatic hydrocarbons, e.g. tetrachloroethylene or monochlorobenzene.

The second stage substitution of the dichloro-alkyl-amino-s-triazine intermediate is carried out at a reduced temperature between 40 and 100"C, preferably between 50 and 80"C, and at normal pressure. In this step, the further alkylamine substitution is carried out by adding a 100% or greater molar excess of monoalkylamine (preferably a 100% molar excess, i.e. an excess of 1 mole) in anhydrous gaseous or liquid form or as aqueous solution, e.g., as an approximately 70% solution in water. One mole of monoalkyamine acts thereby as an acid acceptor, forming one mole each of the active monochloro-diamino-s-triazine (e.g.

2-chloro-4-ethyl-amino-6-isopropylamino-s-triazineoatrazine) and monoalkylamine hydrochloride, which is dissolved in the lower aqueous layer and removed by drawing off this layer. This reaction step can be illustrated as follows:

II Cl /C\N I NH-alkyl I C1-C < + C-NH-alkyl + 2 moles of monoalkylamine dissolved in water reduced temperature C1 C N alkyl-HN-C9 > C-btE-alkyl + monoalkylamine hydrochloride N The monoalkylamine hydrochloride formed, if anhydrous instead of aqueous monoalkylamine is used, may also be removed as a melt at a temperature sufficiently high so that the alkylamine hydrochloride is at or above its melting point, (e.g., at about 110 C or greater in the case of monoethylamine hydrochloride), but provision must be made to minimize formation of tris (alkylamino)-s-triazine compounds, e.g., by rapid heating with the use of, e.g., a coalescer or decanter, to separate the monoalkylamine hydrochloride, followed by rapid cooling. The by-product monoalkylamine hydrochloride may further be removed as a soluble extract in a polyhydroxy or polyether solvent selected from, e.g., ethylene glycol, glycerine, diethylene glycol or polyethylene glycol.

While the above reaction can be carried out using 2 moles of anhydrous monoalkylamine, which may be the same or different from the monoalkylamine used for step I, an undersirable side-reaction occurs at a significant rate between the active monochloro-diamino-s-triazine and anhydrous monoalkylamine of monoalkylamine hydrochloride, resulting in the formation of tris-(alkylamino)-striazine compounds, which are yield-losing and undesirable products in the effluent.

Therefore, it is preferable that water be added to have a partially aqueous monoalkylamine solution so that the formation of tris-(alkylamino)-s-triazine compounds in the side-reaction is much lower and results in only approximately 0.2 to 0.8% or less of these by-products.

It is also of great significance that the small amount of tris-(alkylamino)-striazines as impurity is found in the monoalkylamine hydrochloride/water layers and in successive aqueous extractions.

The organic solvent layer containing up to 25% of monochloro-diamino-striazine (active product) may be freed of solvent by steam stripping to leave a water/monochloro-diamino-s-triazine slurry from which the monochloro-diaminos-triazine product is isolated by filtration (for subsequent grinding and formulation). Alternatively, the bulk of the monochloro-diamino-s-triazine may be removed from the organic solvent layer by cooling to crystallize the active product, which is filtered off to leave a more dilute organic solution. This latter may be further treated to recover additional monochloro-diamino-s-triazine or it may eventually be recycled to the first or second stage of the reactor system.

In the case of the production of 2-chloro-4-ethylamino-6-isopropylamino-striazine (atrazine), the monoethylamine hydrochloride contained in the aqueous layer may be recovered by an "exchange" in several stages of fractionation with isopropylamine. Maintaining an excess of isopropylamine during the exchange, as well as removing the lower boiling monoethylamine (boiling point 16.6"C) from the isopropylamine (boiling point 33 to 340C), facilitates this fractionation.

III M onoethylamine hydrochloride+Isopropylamine It Monoethylamine+lsopropylamine hydrochloride (gas) (recycled to first step) The exchange may be accomplished either with the aqueous monoethylamine hydrochloride extract or with monoethylamine hydrochloride which remains after azeotropic drying with the organic solvent layer. Advantages appear to exist in carrying out the exchange on the aqueous extract because of the homogeneity of the medium. Thereby, the isopropylamine hydrochloride (after fractionation) in the water layer may be treated to remove its tris-(alkylamino)-s-triazine impurities (which are concentrated here and in successive aqueous extracts rather than appearing in the atrazine filtrate which remains after removal of the organic solvent). An alternative is to remove the tris-(alkylamino)-s-triazine impurities prior to amine exchange. The separation of tris-(alkylamino)-s-triazine impurities from isopropylamine hydrochloride/water solution and from successive aqueous extracts may be achieved by several methods known in the art, e.g. extraction with a solvent (CH2C12, CHCl1, CClA, toluene or xylene) or by filtration after an interval of time to allow the tris-(alkylamino)-s-triazines to precipitate, or by absorption on activated material (e.g. carbon). The final, purified isopropylamine hydrochloride/water layer is then dried by removing the water as an azeotrope in an organic solvent to leave a slurry of isopropylamine hydrochloride in the organic solvent which is recycled to the feed of the first step (I) reactor. The fractionated purified monoethylamine may be compressed and stored and then absorbed in water to form the desired concentration of monoethylamine/water for feeding to the second stage (II) reaction above. Direct absorption of the anhydrous monoethylamine in water is another possible means of recycling the monoethylamine.

It is to be noted that the total summation of reactions, I, II and III above is one in which no caustic is consumed: cyanuric chloride+isopropylamine+monoethylamine < 2 r2 - chloro - 4 - ethylamino - 6 - isopropylamino-s-triazine+2 HCI (gas).

Thus, this invention provides a non-caustic-consuming process for manufacturing monochloro-di(monoalkylamino)-s-triazine herbicides, which has, as by-product, hydrogen chloride gas. The gaseous hydrogen chloride has economic value as a chemical intermediate per se, or it may be used in a number of processes for the economic production of chlorine gas. In addition, the process of this invention makes it possible to manufacture for example 2-chloro-4-ethylamino6-isopropylamino-s-triazine, with a very large reduction in the amount of total effluent, which includes such by-products as hydroxy-triazines and tris (alkylamino)-s-triazines, which would be very expensive to remove completely from the whole effluent. A lower total energy consumption might be expected on account of the reduction in the present high consumption of electricity for the intense cooling needed to lower reactor temperatures as in the cyanuric chloride/toluene:caustic/water reaction system. The total yields of monochlorodi(monoalkylamino)-s-triazine range from 97.5 to 99.5% (based on cyanuric chloride) of product containing, e.g., 97 to 99% of 2-chloro-4-ethylamino-6isopropylamino-s-triazine, as well as the low "active" by-product formation of 0.5 to 1% of 2-chloro-4,6-bis(isopropylamino)-s-triazine and 0.5 to 1.5% of 2-chloro 4,6-bis(ethylamino) s triazine, and the ?formation of inactive by-products (or effluent impurities) is from 0 to 0.1 of hydroxy-triazines and 0.2 to 0.8% of tris (alkylamino)-s-triazines (much of this undesirable by-product can be recovered in more concentrated solution for disposal by additional aqueous extractions after removal of the monoethylamine hydrochloride layer).

It can thus, on balance, be demonstrated that the very high conversion of cyanuric chloride to a marketable product makes the caustic-free process for the manufacture of amino-s-triazines economically very advantageous. In addition, effluent treatment costs are very substantially lower compared with those for an aqueous caustic/toluene reaction system.

The following examples illustrate the process of the invention. All the amines and amino groups are mono-substituted by alkyl.

Example 1 a) A 2-liter, 3-neck bottom outlet reactor was equipped with thermometer, mechanical stirrer and Dean-Stark trap, with a N2 sweep over the condenser. Into the flask was charged isopropylamine hydrochloride (63.11 g; 0.65 mole) and 1000 ml of xylene. The mixture was then refluxed for 30 minutes to ensure dryness. The mixture was cooled to approximately 65 to 700C, then cyanuric chloride (119.86 g; 0.65 mole) was added, and an additional 225 ml of xylene. The Dean-Stark trap was replaced with a reflux condenser with a nitrogen sweep vented to a hood or NaOH trap. The reaction mixture was then heated to reflux, and it was observed that HCI began to evolve at approximately 1050C, with the maior portion of this evolution of HC1 occurring at 130 to 1400C. The mixture was kept at reflux until HCI evolution had ceased and the mixture was clear (about 2 to 2.5 hours). Care was taken to react the hydrochloride completely from the reactor walls and stirrer shaft.

b) The reaction mixture was then cooled to 650C and ethylamine (83.57 g of 70% aqueous solution; 1.30 mole) was added dropwise in the course of 30 minutes at 65 to 700 C. The reaction mixture was then stirred for 30 minutes, then heated to form a two-phase solution. The lower aqueous phase was drawn off, then the xylene was removed by steam stripping. The solid product was collected by filtration and dried under vacuum for 12 hours at 600C. Yield: 138.37 g of product containing 97.6% of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, 0.90% of 2-chloro-4,6 bis(isopropylamino)-s-triazine, 0.95% of 2-chloro-4,6-bis(ethylamino)-s-triazine and 0.79% of 2,4-dichloro-6-isopropylamino-s-triazine. Tris(alkylamino)- and -hydroxytriazines were present in an amount of less than 0.05% each. The isolated yield of herbicides was 98.15%.

c) The aqueous monoethylamine hydrochloride extract was extracted once with chloroform, then dried by azeotropic distillation with toluene. The salt was then cooled, filtered and dried to yield 51.50 g of monoethylamine hydrochloride with a melting point of 108 to 1 100C. Yield=97.3%.

Example 2 (Illustration of the Removal of mea.HC1 as a Melt only) A 2-liter, 3-neck bottom outlet reactor equipped with mechanical stirrer, reflux condenser and thermometer was charged with cyanuric chloride (184.4 grams, 1.0 mole) and one liter of xylene. The mixture was cooled to OOC and isopropylamine (59.1 grams, 1.0 mole) was added dropwise maintaining a temperature below 0 C. When the addition was complete, the mixture was refluxed for 2 hours with evolution of HCI.

The resultant solution was cooled to 550 and anhydrous ethylamine (90.0 grams, 2.0 moles) was added dropwise between 55--70"C. When the addition was complete, the mixture was heated to 1200C, and the lower layer of molten ethylamine hydrochloride drawn off. The xylene was then removed by steam stripping, and the product collected by filtration and dried. The yield was 209.93 grams of a product containing 96.4% atrazine, 1.59% propazine, and 1.17% simazine. The isolated yield of herbicide was 96.4% on cyanuric chloride.

79.84 grams of ethylamine hydrochloride was recovered for a yield of 98.9%.

Example 3 A 2-liter 3-neck bottom outlet reactor was equipped with thermometer, mechanical stirrer and Dean-Stark trap, with a N2 sweep over the condenser. Into the flask was charged isopropylamine hydrochloride (62.11 grams, 0.65 m) and 1000 ml of xylene. The mixture was refluxed for 30 minutes with azeotropic removal of water to ensure dryness. The mixture was cooled to approximately 65--70"C, then cyanuric chloride (119.86 gr., 0.65 m) was charged, with an additional 225 ml of xylene. The Dean-Stark trap was replaced with a reflux condenser with a nitrogen sweep vented to a hood. The reaction mixture was then heated to reflux and maintained at reflux until HCI evolution ceased and the mixture was clear, about 2 to 2.5 hours.

The reaction mixture was then cooled to 700C and anhydrous ethylamine (58.5 grams, 1.30 mole) was added dropwise between 60 and 70"C. When the addition was complete, 95 grams of glycerine was added. The mixture was then heated to 95"C, and the lower glycerine layer drawn off. The xylene was then steam-distilled, and the product collected by filtration and dried. The yield was 138.0 grams of a solid containing 96.6% atrazine, 1.67% propazine, 0% simazine. The isolated yield of herbicide was 96.8%. 146.32 grams of glycerine-ethylamine hydrochloride solution was obtained, corresponding to a yield of 97% of monoethylamine hydrochloride.

The following active monochloro-di(monoalkylamino)-s-triazines are produced in an analogous manner with the exception that the amine hydrochloride is not removed prior to removal of the organic solvent: 2-Chloro-4,6-bis(isopropylamino)-s-triazine, commercially available as pror azine herbicide, using either isopropylamine hydrochloride or free isopropylamine in step a) and two equivalents of isopropylamine in step b)to form isopropylamine hydrochloride as a by-product.

Yield=99.7%. 2-Chloro-4,6-bis(ethylamino)-s-triazine, commercially available as simazine herbicide, using either monoethylamine hydrochloride or anhydrous monoethylamine in step a).

Yield=98.8% The invention has been illustrated by way of a few preferred embodiments. It is to be understood, however, that such modifications and variations as would be obvious to persons skilled in the art are within the scope of the appended claims.

WHAT WE CLAIM IS: 1. A process for the preparation of a monochloro-di(monoalkylamino)-striazine which comprises: (I) a first stage, of reacting at a temperature of from 90 to 2000C and normal or elevated pressure, cyanuric chloride and a monoalkylamine hydrochloride in substantially stoichiometric amount to form 2,4 dichloro-6-monoalkylamino-s-triazine and two moles of HCI gas, (II) a second stage, of reacting the solution obtained from state (I) after cooling, at a temperature of from 40 to 1000C and lower than employed in stage (I), and at normal pressure, with a 100% or greater molar excess of a monoalkylamine, to form a monochloro di(monoalkylamino)-s-triazine and monoalkylamine hydrochloride, in which the term "alkyl" means unsubstituted alkyl or alkoxy-substituted alkyl.

2. A process according to claim 1, wherein the reaction of stage (I) is performed in an aromatic hydrocarbon, chlorinated aliphatic hydrocarbon or chlorinated aromatic hydrocarbon solvent and at a pressure of 1 to 10 atmospheres.

3. A process according to claim 2, wherein the reaction of stage (I) is performed at a temperature between 120 and 150"C, in toluene, o-xylene, mxylene, p-xylene, or a mixture thereof, monochlorobenzene or tetrachloroethylene and the reaction of stage (II) is performed at a temperature of 50 to 80"C.

4. A process according to Claim 1, 2 or 3 wherein the 100 > or greater excess of alkylamine in stage II is in aqueous solution.

5. The process according to Claim 4, wherein the monoalkylamine hydrochloride by-product is removed by drawing off the aqueous layer wherein it is dissolved.

6. A process according to Claim 1, 2 or 3 wherein the 100% or greater excess of alkylamine in stage II is charged in anhydrous gaseous or liquid form.

7. A process according to Claim 6, wherein the monoalkylamine hydrochoride by-product is removed as a molten liquid at a temperature at least as high as its melting point, with rapid heating to melt temperature and rapid cooling after drawing off the melt.

8. A process according to Claim 6 wherein the monoalkylamine hydrochloride by-product is removed as a soluble extract in a polyhydroxy or polyether solvent selected from ethylene glycol, glycerine, diethylene glycol or polyethylene glycol.

9. A process according to any preceding claim wherein the monoalkylamines are selected from methylamine, ethylamine, n-propylamine, isopropylamine, 1,2dimethyl-n-propylamine, I-methyl-2-methoxyethylamine.

10. A process according to claim 9, wherein the monoalkylamine of State I is ethylamine or isopropylamine and the monoalkylamine of Stage 11 is ethylamine or isopropylamine.

11. A process according to claim 10, for the preparation of 2-chloro-4ethylamino-6-isopropylamino-s-triazine.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. solution was obtained, corresponding to a yield of 97% of monoethylamine hydrochloride. The following active monochloro-di(monoalkylamino)-s-triazines are produced in an analogous manner with the exception that the amine hydrochloride is not removed prior to removal of the organic solvent: 2-Chloro-4,6-bis(isopropylamino)-s-triazine, commercially available as pror azine herbicide, using either isopropylamine hydrochloride or free isopropylamine in step a) and two equivalents of isopropylamine in step b)to form isopropylamine hydrochloride as a by-product. Yield=99.7%. 2-Chloro-4,6-bis(ethylamino)-s-triazine, commercially available as simazine herbicide, using either monoethylamine hydrochloride or anhydrous monoethylamine in step a). Yield=98.8% The invention has been illustrated by way of a few preferred embodiments. It is to be understood, however, that such modifications and variations as would be obvious to persons skilled in the art are within the scope of the appended claims. WHAT WE CLAIM IS:

1. A process for the preparation of a monochloro-di(monoalkylamino)-striazine which comprises: (I) a first stage, of reacting at a temperature of from 90 to 2000C and normal or elevated pressure, cyanuric chloride and a monoalkylamine hydrochloride in substantially stoichiometric amount to form 2,4 dichloro-6-monoalkylamino-s-triazine and two moles of HCI gas, (II) a second stage, of reacting the solution obtained from state (I) after cooling, at a temperature of from 40 to 1000C and lower than employed in stage (I), and at normal pressure, with a 100% or greater molar excess of a monoalkylamine, to form a monochloro di(monoalkylamino)-s-triazine and monoalkylamine hydrochloride, in which the term "alkyl" means unsubstituted alkyl or alkoxy-substituted alkyl.

2. A process according to claim 1, wherein the reaction of stage (I) is performed in an aromatic hydrocarbon, chlorinated aliphatic hydrocarbon or chlorinated aromatic hydrocarbon solvent and at a pressure of 1 to 10 atmospheres.

3. A process according to claim 2, wherein the reaction of stage (I) is performed at a temperature between 120 and 150"C, in toluene, o-xylene, mxylene, p-xylene, or a mixture thereof, monochlorobenzene or tetrachloroethylene and the reaction of stage (II) is performed at a temperature of 50 to 80"C.

4. A process according to Claim 1, 2 or 3 wherein the 100 > or greater excess of alkylamine in stage II is in aqueous solution.

5. The process according to Claim 4, wherein the monoalkylamine hydrochloride by-product is removed by drawing off the aqueous layer wherein it is dissolved.

6. A process according to Claim 1, 2 or 3 wherein the 100% or greater excess of alkylamine in stage II is charged in anhydrous gaseous or liquid form.

7. A process according to Claim 6, wherein the monoalkylamine hydrochoride by-product is removed as a molten liquid at a temperature at least as high as its melting point, with rapid heating to melt temperature and rapid cooling after drawing off the melt.

8. A process according to Claim 6 wherein the monoalkylamine hydrochloride by-product is removed as a soluble extract in a polyhydroxy or polyether solvent selected from ethylene glycol, glycerine, diethylene glycol or polyethylene glycol.

9. A process according to any preceding claim wherein the monoalkylamines are selected from methylamine, ethylamine, n-propylamine, isopropylamine, 1,2dimethyl-n-propylamine, I-methyl-2-methoxyethylamine.

10. A process according to claim 9, wherein the monoalkylamine of State I is ethylamine or isopropylamine and the monoalkylamine of Stage 11 is ethylamine or isopropylamine.

11. A process according to claim 10, for the preparation of 2-chloro-4ethylamino-6-isopropylamino-s-triazine.

12. A process according to claim 10 for the preparation of 2-chloro-4,6

bis(isopropylamino)-s-triazine or of 2-chloro-4,6-bis(ethylamino)-s-triazine.

13. A process according to Claim I substantially as described in any one of Examples 1 to 3.

14. A monochloro-di(monoalkylamino)-s-triazine wherein "alkyl" is as defined in claim 1, when produced by the process of any of Claims I to 13.

15. 2 - Chloro - 4 - ethylamino - 6 - isopro-ylamino - s - triazine, 2 chloro - 4,6 - bis(isopropylamino) - s - triazine, or 2 - chloro 4,6 - bis(ethylamino) - s - triazine when produced by the process of any of claims 1 to 13.