CA1092115A - Caustic-free process for the production of monochlorodiamino-s-triazines - Google Patents

Abstract

A CAUSTIC-FREE PROCESS FOR THE PRODUCTION OF
MONOCHLORO-DIAMINO-S-TRIAZINES

Abstract of the Disclosure A new and improved process is provided for preparing monochloro-diamino-s-triazines which are useful as herbicides.
The process comprises reacting in A first stage cyanuric chloride and a selected primary alkylamine at elevated temperature to give a dichloro-monoalyl-amino-s-triazine and reacting in a second stage this dichloro-monoalkylamino-s-triazine with an excess of a primary alkylamine which may be introduced as a pure liquid, as gas or as a solution in water. The process gives consistent yields in excess of 97% of monochloro-diamino-s-triazines. Because of the anhydrous conditions in the new caustic-free process and the feasibility of recycling the excess of monoalkylamines employed, no serious effluent problems arise.

Description

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The present inven~ion relates to a new and improved procedure for the preparation of monochloro-diamino-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 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-txiazine, which is commercially usefuI 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-6-isopropylamino-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-6-isopropylamino-s-triazine intermediate compound in accor-dance With the foll~wing reaction:
A) CN' ~ Cl+ /C~N~2 I N~O~ -NH-C~ I NaC1 + ~2 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:

~ - 2 -.~ ., Cl Cl ~ ~ NH C~ 3 + C H N~ M OH ~ ~ C\ CH3 ~N CH3 2 5 2 C2H5HN~ NH-C~ ~ NaCl ~H O

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 ~r the formation of various by-products, such as,.2~chloro-4,6-bis-isopropylamino-s-triazine. The un--desired formation of the last mentioned material, where the preparation of the atrazine product is concerned, may proceed in accordance with the following reaction scheme:

C~
Cl CH3 CH3\ ~1 ~N CH3 CH3 ~ .

CH ~ N ~N ~ NH C~ ~ NaCl+~20 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-6-isopropylamino-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 ZllS

highly desirable to produce the 2-chloro-4,6-diamino-s-triazines in high yield and purity wi.thout creating problems in effluent treatment and disposal because of the aqueous NaCl and other triazine by-products contained in the aqueQus effluent of the above described process of manu-facture.
U.5. Patent No. 3,328,399 discloses a process for preparing amino-s-triazines without neutralizing the HCl formed in the reaction. However, this patent discloses only a method involving reacting cyanuric chloride with secondary amines in an anhydrous system and the HCl formed is distilled off from the reaction mixture.

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

According to the present invention monochloro-diamino-s-triazines are produced i.n high yield and purity, with a reduced consumption of energy and reactants, by a process which comprises:
a) reacting at elevated temperature and normal or elevated pressure, and in an inert organic solvent, cyanuric chloride and a monoalkylamine hydrochloride in substantially stoichiometric amounts to form.2,4-dichloro-6-alkylamino-s-triazine and two moles of hydrogen chloride gas, b) reacting the solution of step a) at less elevated temperature and normal pressure with 100% or greater excess of a monoalkylamine to form a monochloro-diamino-s-triazine and mono-alkylamine hydrochloride.

...,l .. . i 1~)9Z~L15 The process according to the present invention proceeds according to the following reaction scheme:

Cl N ~ N
Il ¦ elevated temp.
Cl ~ /r Cl ~ alkyl-NH2-HCl N solvent N
Cl ~ /~ NH-alkyl + 2HCl (gas~

II

N ~
Ci ~ ~ H-alkyl + 2 alkyl-NH elevated temp.

Cl (aqu. solution) ~ N
alkyl-NH ~ /~ NH-alkyl + alkyl-NH2-HCl Examples of preerred monoalkylamines are:
methylamine, ethylamine, n-propylamine, isopropylamine, 1,2-dimethyl-n-propylamine, 1-methyl-2-methoxy-ethylamine.
The process step I is preferably performed at a reaction temperature between about 90 and 200C, more preferably :~1 .~ .. i ~39Z~L5 between 120 and 150C, at normal or elevated pressure, e.g., 1 to 10 atmosphere. Suitable inert organic solvents for this process step are aromatic hydrocarbons, for example, toluene, o-xylene, m-xylene, p-xylene or a mixture thereof, or chlorinated aliphatic or aromatic hydrocarbons, such as, tetrachloroethylene or monochlorobenzene.
The second step substitution o~ the dichloro-alkyl-amino-s-triazine intermediate is preferably carried out at a temperature between about 40 and 100C, more prefer-ably between 50 and 80C, and at normal pressure. In this step, the ~urther alkylamine substitution is carried out by adding an excess of monoalkylamine Ipreferably 1 mole) in anhydrous gaseous or liquid form or as aqueous solution, e.g., as an approximately 70% solution in water. One mole of monoalkylamine acts thereby as an acid acceptor, forming one mole each of the active monochloro-diamino-s-triaaine (e.g. 2-chloro-~-ethylamino-6-isopropylamino-s-triazine ~ > atrazine) and monoalkylamine hydrochloride, which is dissolved in the lower aqueous layer and removed by drawing off this layer.

The monoalkylamine hydrochloride formed, if anhydrous instead ofaqueous 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 110C or greater in the case of monoethylamine hydrochloride), but provision must be made to minimize formation of tris-(alkylamino)-s-triazine compounds, e.g.l by rapid heating with the use of, e.g., a coalescer or decanter, to separate the monoalkyl-amine hydrochloride, followed by rapid cooling. The by-product monoalkylamine hydrochloride may further be removed . ..

1(39Zl~S

as a soluble extract in polyhydroxy or polyether solvents 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 monoalkyIamine used for step I, an undesirable side-reaction occurs at a significant rate between the active monochloro-diamino-s-triazine and anhydrous monoalkylamine or monalkylamine hydrachloride, resuIting in the formation of tris-~alkylamino~-s-triazine 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-tr.iazine compounds in the side-reaction is much lower and results in only approximately 0.2 to 0.8% or less of these by-products.

1~2~5 : ' It is also of great significance that the small amount of tris-talkylamino)-s-triazines as impurity is found in the monoallcylamine hydrochloride/water layers and in successive aqueous extractions.
S The organic solvent layer containing ~lp to 25% of monochloro-diamino-s-triazine (active product) may be freed of solvent by steam stripping to leave a water/
monochloro-diamino-s-triazine slurry from which the mono-chloro-diamino-s-triazine product is isolated by filtration tfor subse~uent 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 -15 ~urther treated to recover additional monochloro-diamino-.
s-triazine or it may eventually be recycled to the first cr second stage of the reactor system.
In ~he case o~ the production of 2-chloro-4-ethylamino~6-isopropylamino~s-triazine ~atrazine), the monoathylamine hydrochloride contained in the aqueous layer may be recovered by an l'exchange" in several stages of fractionation wi~h isopropylamine. Maintaining an excess of isopropylamine during the exchange, as well as removing the lower boiling monoethylamine (boiling point 16.6C) from the isopropylamine ~boiling point 33 to 34JC), facilitates thls fractionation.

.. ... .

~8--Z~15 This exchange proceeds according to the ~ollowing reaction scheme:
III
CH3\ ~ CH /CH NH2~HCl-~C2H5-MH (~as) The exchange may be accomplished either with the aqueous monoethylamine hydrochloride extract or with mono-ethylamine hydrochloride whi~h remains after azeotropic drying with the organic solvent layer. Advantages appear to exist in carr~ing out the exchange while still containing water because o the homogeneity of the medium. Thereby, the isopropylamine hydrochloride tafter fractionation) in the water layer may be treated to remove its tris-(alkyl-amino)-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 i tris-(alkylamino)-s-triazine impurities from i~oprop~-lamine hydrochloride/water solution and from successive aqueous extracts may be achieved by several methods known in the art, such as, extraction with a solvent (CH2C12, CHC13, CC14, toluene or xylene, etc.) or by filtration after an inter~al of time to allow the tris-(alkylamino)-s-triazines t~ precipitate, or by absorption on activated material ~e.g., carbon). The final, purified _ g _ .

l~D~L15 isopropylamine hydrochloride/water layer is then dried by removing the water as an azeotrope in an or~anic solvent to leave a slurry of isopropylamine hydrochloride in the organic solven~ 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 - ~orm 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 o~ 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 oonsumed: cyanuric chloride ~ isopropylamine ~ monoethyl-~nine - --7 2-chLoro-4-ethylamino-6-isopropylamino-s-triazine + 2 HCl (gas).
Thus, this invention provides a non-caustic-consuming process for manufacturing monochloro-dialkylamino-s-triazine herbicides, which has, as by-product, hydrogen chioride gas. The gaseous hydrogen chloride has economic value as a chemical interrnediate per se, or it may be used in a nurnber 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-ethylamino-6-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 " .

9.'~ LS
from the whole effluent. A lower total energy consumption might be ex~ected on account of the reduction in the present high consumption of electricity fo~ the intense cooling needed to lower reactor temperatures as in the cyanuric chloride/toluene:caustic/water reaction system. The total yields of monochloro-dialkylamino-s-triazine range from 97.5 to 99.5~ (based on cyanuric chloride) of product containing, e.g., g7 to 99% of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, as well as the low "active"
by-product formation o 0.5 to 1% of 2-chloro-4,6-bisliso-propylamino)-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 effluen~ impurities) is from 0 to 0.1% of hydxoxy-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 mono-ethylamine hydrochloride layer).
It can thus, on balance, be demonstrated that the very high con~ersion 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 non-limitative examples will serve to illustrate the process of the invention.

3'~
.

Example 1 a) A 2-liter, 3~neck bottom outlet reactor was equipped with thermometer, mechanical stirrer and Dean-Stark trap, wi~h 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 ref~uxed for 30 minutes to ensure dryness. The mixture was ccoled to approximately 65 to 70C, 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 wa5 then heated to reflux, and it was ol~served that HCl began to evolve at approximately 105C, with the major portion of this evolution of HCl occuring at 130 to 140C. The mixture was kept at reflux until HCl evolution had ceased and the mixture was clear (about 2 to 2.5 hours). Case was taken to react the hydrochloride completely from the reactor walls and stirrer shaft.
-- h) The reaction mixture was then cooled ~o 65C and monoethylamine (83.57 g of 70% aqueous solution; 1.30 mole) was added dropwise in the course of 30 minutes at 65 to 70C.
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 60C. Yield: 138.37 ~ o~ product containing 97.6% of 2-chloro-4-ethylamino-6-isopropylamino-s-` -~2 S

triazine, 0.90% of 2-chloro-4,6~bis(isopropylamino)-s-tria-zine, 0.95% of 2-chloro-4,6-bis~ethylamino)-s-triazine and 0.79% of 2,4-dichloro-6-isopropylamino-s-triazine. Trialkyl-amino- and hydroxy-triazines 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 hydro-chloride with a melting point of 108 to 110C. Yield = 97.3%.
Example 2 (Illustration of the Remo~al of MEA-HCl as a Melt only) A 2-liter, 3-neck bottom ou~let 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 0C
and isopropylamine (59.1 grams, 1.0 mole) was added dropwise maintaining a temperature below 0C. When the addition was complete, the mixture was refluxed for 2 hours with evolution of ~Cl.
The resuItant solution was cooled to 55 and anhydrous monoethylamine (90.0 grams, 2.0 moles) was added dropwise between 55-70C. When the addition was complete, the mixtu~e was heated to 120C, and the lower layer of m~lten monoethyl~mine hydrochloride drawn off. The xylene was then removed by steam stripping, and the product collected by filtration and dried. T~e 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.

Z~l~

79,84 grams o~ monoethyLamine hydrochloride wasrecovered for a yield of 98.9%.

Example 3 A ~-liter 3~neck bottom outlet reactor was equipped with thermometer, mechanlcal stirrer and Dean-Stark trap, with a N2 sweep over the condenser. Into the flask was charged isopropylamine hy~rochloride (62.11 grams, 0.65m) and 1000 ml of xylene. The mixture was refluxed for 30 minutes with azeotropic removal of water to insure dryness.
The mixture was cooled to approximately 65-70C, then cyanuric chloride (119.86 gr., 0.65m) was charged, with an additional 225 ml of xylene. The Dean-Stark trap was re-placed 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 HCl evolution ceased and mixture was clear, about 2 to 2.5 hours.

The reaction mixture w~as then cooled to 70C and anhydrous monoethylamine (58.5 grams, 1.30 mole) was added dropwise between 60 and 70C. When the addition was complete, 95 grams of glycerine was added. The mixture was then heated to 95C, and the lower glycerine layer dra~n off. The xylene was then stPam-distilled, and the product collected by ~iltration and dried. The yield was 138.0 grams of a solid containing 96.6~ atrazine, 1.67~
propaæine, 0% simazine. The isolated yield of herbicide was 96.8%. 146.32 grams of glycerine-monoethylamine hydro-chloride solution was obtained, corresponding to a yield of 97~ of monoethylamine hydrochloride.
The following ac~ive monochloro-diamino-s-tria-zines are produced in an analogous manner with the ~092~L~S

exception that the amine hydrochlorlde is not removed prior to removal of the organic solvent:
2-Chloro-4,6-bis(isopropylamino)-s-triazine, commercially available as propazine 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 monoethyl-amine 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 s~iIled in the art are within the scope of the appended claims.

Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A two-stage process for the preparation of a mono-chloro-diamino-s-triazine which comprises:
(a) reacting at elevated temperature and normal or elevated pressure, and in an organic solvent, cyanuric chloride and an alkylamine hydrochloride in substantially stoichiometric amounts to form 2,4-dichloro-6-alkylamino-s-triazine and two moles of HCl gas, and (b) reacting the solution of step (a) at a less elevated temperature and normal pressure with a 100% or greater excess of an alkylamine to form a monochloro-diamino-s-triazine and monoalkylamine hydrochloride.

2. A process according to claim 1, wherein the reaction of step (a) is performed at a temperature between 90 and 200°C, in an aromatic hydrocarbon or chlorinated aliphatic hydrocarbon or chlorinated aromatic-hydrocarbon solvent and at normal pres-sure or at a pressure of 1 to 10 atmospheres, and the reaction of step (b) is performed at a temperature between 40 and 100°C.

3. A process according to claim 2, wherein the reaction of step (a) is performed at a temperature between 120 and 150°C, in a solvent selected from toluene, o-xylene, m-xylene, p-xylene, or a mixture thereof, or monochlorobenzene or tetrachloroethyl-ene and the reaction of step (b) is performed at a temperature of 50 to 80°C.

4. A process according to Claim 1, wherein the 100%
or greater excess of alkylamine in step b) 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, wherein the 100 or greater excess of alkylamine in step b) 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 polyhydroxy or polyether solvents selected from ethylene glycol, glycerine, diethylene glycol or polyethylene glycol.

9. A process according to cla:im 1, wherein the alkylamines of steps a) and b) are selected from methylamine, ethylamine, n-propylamine, isopropylamine, 1,2-dimethyl-n-prop.ylamine, 1-methyl-2-methoxyethylamine.

10. A process accoxding to claim 1, wherein the alkylamine of step a) is ethylamine or isopropylamine and the alkylamine of step b) is ethylamine or isopropylamine.

11. A process according to claim 1 for the preparation of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine.

12. A process according to claim 1 for the preparation of 2-chloro-4,6-bis(isopropylamino)-s-triazine or of 2-chloro-4,6-bis(ethylamino)-s-triazine.