Note: Descriptions are shown in the official language in which they were submitted.
~Q~ S
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 -
.~ .,
109211S
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.
-- 4 --
...,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
-- 6 --
. ..
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
" .
--10--
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.
-13-
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
- 14 -
~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.
