Note: Descriptions are shown in the official language in which they were submitted.
2060049
HOECHST AgTIENGESELLSCHAFT HOE 91/F 901 Dr.GL-nu
Werk Gendorf
Process for the preparation of dialkylaminopropanediol
Description
The invention relates to a process for the preparation of
dialkylaminopropanediol by reaction of monohalopropane-
diol with excess dialkylamine in the presence of water.
Such a process is described in US Patent 2,147,226,monochloropropanediol (glycerol monochlorohydrin) and
dimethylamine being employed as starting compounds. The
equation below using said starting compounds is intended
to illustrate the reactions
CH2-Cl CH2-NtCH3)2
CX-O~ + ICH~)2NH C~-OH ~ XCl
CH2-OH CK2-OH
According to ~S Patent 2,147,226, the dimethylamine is
employed in an amount of up to 1.5 mol per mole of
glycerol monochlorohydrin. The reaction, which occur~ in
an exothermic manner, is carried out at a temperature of
20 to 50C and in the presence of a relatively large
amount of water (in the exemplary embodiments, the
dimethylamine is employed in the form of a 24.5% strength
aqueous solution, i.e. 75.5% by weight of water, relative
to the mixture of dimethylamine and water). The hydro-
chloric acid liberated during the reaction is bound by an
alkali metal hydroxide which is likewise employed in the
form of an aqueous solution. This process is thus carried
out using a low concentration of dimethylamine and
consequently using a large amount of water. This repre-
sents a substantial deficiency of this process. A further
disadvantage is that the reaction time is relatively long
and the yield of dimethylaminopropanediol, relative to
glycerol monochlorohydrin, is low in spite of this. A
yield of 98% of theory admittedly results from the single
2060043
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example. However, it was not possible to confirm this
high value by reworking the example.
In said US Patent 2,147,226, prior art is mentioned at
the start according to which dimethylaminopropanediol has
been prepared in the laboratory by heating glycerol
monochlorohydrin and dimethylamine to 100C in a closed
tube. Undesired by-products are formed at this relatively
high temperature. Compared with this anhydrous manner of
preparation, that of said US patent i6 thus more
advantageous.
The invention is accordingly based on the object of
improving the process known from US Patent 2,147,226 and
based on a low reaction temperature, in particular with
respect to amount of water, reaction time and yield.
The process according to the invention comprises employ-
ing the dialkylamine in an amount of at least 2.5 mol per
mole of monohalopropanediol, preferably in an amount of
3 to 6 mol per mole of monohalopropanediol, and carrying
out the reaction in the presence of 25 to 70% by weight
of water, preferably 30 to 60% by weight of water,
relative to the mixture of dialkylamine and water, and at
a temperature of 20 to 80C, preferably 30 to 60C, and
recovering the desired dialkylaminopropanediol from the
reaction product.
In the process according to the invention, the reaction
of the dialkylamine and the halopropanediol is thus
carried out in the presence of a very specific amount of
water. Thus, reaction at the given temperature in the
case of less than 25% of water, relative to the mixture
of dialkylamine and water, simply comes to a stop after
a reaction time of greater or lesser length. Using more
than 70~ by weight of water, a relatively short reaction
time is in fact achieved, but the space-time yield is
impaired. The amount of water (the aqueous medium) thus
represents a critical quantity of the process according
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to the invention and i8, as stated above, 25 to 70% by
weight, preferably 30 to 60~ by weight, percentages by
weight relative to the sum of dialkylamine and water
employed.
Additionally, in the proces6 according to the invention
the dialkylamine is employed in an amount of at least
2.5 mol per mole of halopropanediol. Undesired by-pro-
ducts are formed even at a relatively low molar ratio.
The upper amount of dialkylamine can vary within a wide
range. As a rule, not more than 6 mol of dialkylamine
will be employed per mole of halopropanediol. The amount
of dialkylamine is therefore preferably 3 to 6 mol of
dialkylamine per mole of monohalopropanediol.
The reaction temperature suited to the stated amount of
water and amount of dialkylamine to achieve the desired
effect is 20 to 80C. Below 20C, the reaction time is
already relatively long and above 80C the formation of
by-products can occur. The preferred reaction temperature
is therefore 30 to 60C.
As far as the binding of the hydrohalic acid formed in
the reaction is concerned, the amine compounds present
are used for this. The hydrohalic acid is thus bound in
the process according to the invention by the amine
present in the system itself and not by alkali metal
hydroxides (i.e. extraneous basic compounds), as in the
prior art.
To carry out the process according to the invention, the
dialkylamine and the halopropanediol are brought into
contact in the stated molar ratio and in the stated
amount of water and at the stated reaction temperature.
The manner of bringing into contact is not critical per
se. The following forms of implementation (1 to 4) are
preferred: (1) all of the dialkylamine, halopropandediol
and water are added to a reaction vessel and kept at the
temperature stated until all the halopropanediol has been
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reacted; (2) all of the dialkylamine and the water are
initially introduced. The mixture i8 brought to reaction
temperature, after which the halopropanediol is added
thereto as ~uch (in portions or continuously) at this
S temperature. After addition, the mixture i9 additionally
kept at reaction temperature for the subsequent reaction;
(3) all of the halopropanediol and the water are
initially introduced. The mixture i6 brought to reaction
temperature, after which the dialkylamine is added
thereto as such at this temperature. After the addition,
the mixture is additionally kept at reaction temperature
for the subsequent reaction (4) all of the
halopropanediol is initially introduced and brought to
reaction temperature, after which the dialkylamine and
the water are added thereto at this temperature,
separately from one another or together in the form of an
aqueous dialkylamine solution. After the addition, the
mixture is additionally kept at reaction temperature for
the subsequent reaction. The reaction between the
dialkylamine and halopropanediol is exothermic. In the
case of a low-boiling dialkylamine compound, such as
dimethylamine, which has a boiling point of 7C at normal
pressure, the reaction is carried out in a pressure
vessel, as more or less high vapor pressures have to be
taken into account at said reaction temperatures. The
reaction time is 2 to 10 hours and in particular depends
on the amount of water and reaction temperature chosen.
If it is desired to work up the reaction product obtained
by the process according to the invention and to recover
the dialkylaminopropanediol compound, this is preferably
carried out by the following method: the dialkylamine and
the water are first removed by distillation from the
reaction product, which is essentially composed of
dialkylaminopropanediol . HX (X = halogen), the dialkyl-
amine employed in excess and water, after which thedialkylaminopropanediol hydrohalide product is present in
high purity. To liberate the dialkylaminopropanediol, the
hydrohalide compound is treated for neutralization
206~049
purposes with about 1 molar equivalent of alkali metal
hydroxide, preferably potassium hydroxide or sodium
hydroxide, expediently in the form of a 30 to 60% by
weight aqueous solution, the temperature of the mixture
being kept at preferably 20 to 60C by cooling. The
dialkylaminopropanediol (expediently after filtering off
or centrifuging off the main paxt of the salt) can be
recovered simply by distillative working up of the
mixture of dialkylaminopropanediol, water and salt then
present. As the dialkylaminopropanediol is present in
high purity in said mixture, the distillative isolation
of the dialkylaminopropanediol iB often not necessary at
all. In this case, the relatively complicated steps,
filtration or centrifugation, if necessary washing, and
finally distillation, can be dispensed with. The above-
mentioned dialkylaminopropanediol hydrohalide which is
obtained in high purity is also already an advantageous
starting material for subsequent reactions.
The starting compounds of the reaction according to the
invention are monohalopropanediol and dialkylamine.
Dialkylamine in the context of the present invention is
understood as meaning the lower dialkylamines, preferably
dimethylamine and diethylamine. All these compounds are
known and commercially available. Said dialkylamines are
liquids having a boiling point of 7C (dimethylamine) and
50C (diethylamine) at normal pressure. The particularly
preferred dialkylamine is dimethylamine. As is known,
halopropanediol exists in two structural forms, in
particular as 3-halopropane-1,2-diol or as 2-halopropane-
1,3-diol, the first mentioned compound being much the
more frequent. The formulae below are intended to illu-
strate the two structures, where X i8 a halogen:
- 6 - 2060049
f~2-X ~a-~
CH-OH CH-X
l~2 ~ CHa-~
3-halopropane- 2-halopropane-
1,2-diol 1,3-diol.
The halopropanediols are also liquids. As chlorine is the
usual halogen, 3-chloropropane-1,2-diol, whose boiling
under normal pressure is 213C, i8 the preferred com-
pound. The dialkylaminopropanediol prepared by the
process according to the invention is therefore prefer-
ably a dimethylaminopropanediol, in particular 3-
dimethylaminopropane-1,2-diol.
The process according to the invention has a number of
advantages compared with the prior art. The reaction can
be carried out with a substantially higher concentration
of dialkylamine or, expressed in another way, with a
substantially lower water content. The reaction time is
additionally much shorter. A high space-time yield is
obtained because of the higher dialkylamine concentration
and the shorter reaction time. The chemical yield of
dialkylaminopropanediol, relative to glycerol monohalo-
hydrin employed, is also very high. As a rule, it is 91to 97%. A further advantage of the process according to
the invention is the high purity of the dialkylaminopro-
panediol obtained. It can frequently be reused without
distillative working up. In a distillative fine purifica-
tion, only very little residue is produced. Said advan-
tages also result when a crude halopropanediol is used as
starting material, i.e. for example a chloropropanediol
as is obtained by hydrolysis of epichlorohydrin, in
particular without further purification of the hydrolysis
product, can rather be employed as such. All these
surprising effects of the process according to the
invention obviously result from the combination of the
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measures described. The process according to the
invention can additionally be carried out batchwise or
continuously.
Dialkylaminopropanediol6, such a6 dimethyl- and diethyl-
aminopropanediol, are useful intermediates because of
their trifunctionality.
The invention will now be illustrated in greater detail
by examples.
Example 1
900.0 g (20.0 mol) of dimethylamine and 385.7 g of water
(i.e. 30.0% by weight of water, relative to dimethylamine
plus water) were initially introduced into a reaction
vessel and warmed to 30C with stirring (the following
operations were also carried out with stirring; this also
applies to all other examples). 734.8 g (6.65 mol) of
3-chloropropane-1,2-diol were continuously added to this
mixture in the course of about 2 hours while maintaining
a temperature of 30 to 35C. After the addition of
chloropropanediol, the mixture was kept at said tempera-
ture for a further 7 hours for subsequent reaction, after
which all of the chloropropanediol had reacted (the
pressure in the reaction vessel, which essentially
results from the vapor pressure of the dimethylamine, was
0.15 to 0.20 MPa).
The working up of the reaction product was carried out as
follows: the excess dimethylamine and a large part of the
water were first removed from the reaction product
(contents of the reaction vessel) by distillation at
normal pressure and a temperature of at most 115C. The
water was further removed by distillation in a water pump
vacuum at 0.005 MPa. The mixture of dimethylaminopropane
hydrochloride and water then present (about 2% by weight)
was treated in the course of one hour with a stoichiomet-
ric amount of sodium hydroxide, relative to
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chloropropanediol employed (i.e. 6.65 mol of NaOH), in
the form of an approximately 50% strength by weight
solution whilst stirring and maintaining a temperature of
at most 50C to release the dimethylaminopropanediol from
the hydrochloride. The precipitated salt was removed from
the mixture composed of dimethylaminopropanediol, water
and precipitated sodium chloride by filtration at room
temperature. The filter cake was washed three times with
isopropanol (250 ml, 200 ml and 150 ml), after which the
individual filtrates were combined. The water and the
isopropanol were removed from the mixture of dimethyl-
aminopropanediol, water and isopropanol by distillation
in a water pump vacuum at a temperature of up to 100C.
The 3-dimethylaminopropane-1,2-diol of boiling point 74
to 75C at 122 Pa was then distilled over. 734.3 g
(6.16 mol) of pure product were obtained, i.e. 92.6% of
the theoretical yield. The product had a purity of 99.8%.
Example 2
900.0 g (20.0 mol) of dimethylamine and 385.7 g of water
(i.e. 30.0% by weight of water, relative to dimethylamine
plus water) were initially introduced into a reaction
vessel and heated to 40C with stirring. 553.0 g
(5.0 mol) of 3-chloropropane-1,2-diol were continuously
added to this mixture in the course of approximately
1.5 hours while maintaining a temperature of 40 to 50C.
After the addition of the chloropropanediol, the mixture
was kept at said temperature for a further 5 hours for
subsequent reaction, after which all of the chloro-
propanediol had reacted (the pressure in the reaction
vessel was approximately 0.2 NPa). The reaction product
was worked up analogously to Example 1. 559.0 g
(4.69 mol) of 3-dimethylaminopropane-1,2-diol of boiling
point 93C at 0.7 to 0.9 kPa were obtained, i.e. 93.8% of
theory. The dimethylaminopropanediol had a purity of
99.5%.
2060049
g
Example 3
900.0 g (20.0 mol) of dimethylamine, 900.0 g of water
(i.e. 50.0% by weight of water, relative to dimethylamine
plus water) and 443.0 g (4.0 mol) of 3-chloropropane-1,2-
diol were initially introduced into a reaction vesselwith ~tirring and cooling and ad~usted to a temperature
of 50 to 55C. The mixture was kept at said temperature
for 6 hours with stirring. After this time, all of the
chloropropanediol had reacted.
The reaction product was worked up analogously to Example
1. 464.8 g (3.90 mol) of 3-dimethylaminopropane-1,2-diol
of boiling point 89C at 0.6 to 0.8 kPa were obtained,
i.e. 97.5% of theory. The dimethylaminopropanediol had a
purity of 99.5%.
Example 4
443.0 g (4.0 mol) of 3-chloropropane-1,2-diol were
initially introduced into a reaction vessel and heated to
40C with stirring. 900.0 g (20.0 mol) of dimethylamine
and 1,350.0 g of water (i.e. 60% by weight of water,
relative to dimethylamine plus water) were continuously
added simultaneously and separately from one another to
the heated chloropropanediol in the course of 1 hour
while maintaining a temperature of 40 to 45C. After this
addition, the mixture was kept at said temperature for a
further 4 hours for subsequent reaction, after which all
of the chloropropanediol had reacted.
The reaction product was worked up analogously to Example
1. 463.6 g (3.89 mol) of 3-dimethylaminopropane-1,2-diol
of boiling point 93C at 0.7 to 0.9 kPa were obtained,
i.e. 97.3% of theory. The dimethylaminopropanediol had a
purity of 99.5%.
Example 5
443.0 g (4.0 mol) of 3-chloropropane-1,2-diol were
initially introduced into a reaction vessel and heated to
2060049
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35C with stirring. 450.0 g (10.0 mol) of dimethylamine
and 675.0 g of water (i.e. 60% by weight of water,
relative to dimethylamine plus water) were continuously
added simultaneously and separately from one another to
the heated chloropropanediol in the course of 1.5 hours
while maintaining a temperature of 35 to 40C. After this
addition, the mixture was kept at said temperature for a
further 5 hours for subsequent reaction, after which all
of the chloropropanediol had reacted.
The reaction product was worked up analogously to Example
1. 435.1 g (3.65 mol) of 3-dimethylaminopropane-1,2-diol
of boiling point 89C at 0.6 to 0.8 kPa were obtained,
i.e. 91.3% of theory. The dimethylaminopropanediol had a
purity of 99.5~.
Comparison example (reworking of the example of US Patent
2,147,226)
3.986 kg of a 24.5% strength aqueous dimethylamine
solution (i.e. 0.977 kg or 21.71 mol of dimethylamine)
and 0.679 kg of a 40% strength aqueous sodium hydroxide
solution (i.e. 0.272 kg or 6.80 mol of NaOH) were mixed
together in a reaction vessel with stirring and cooling.
Altogether 1.812 kg of glycerol l-monochlorohydrin (i.e.
16.40 mol) were added in 0.091 kg portions in the course
of 15 minutes in each case. The reaction mixture was kept
at 20 to 40C the whole time. The pressure in the reac-
tion vessel rose to 0.1 MPa. The mixture was allowed to
stand for 24 hours, after which 0.679 kg of a 40%
strength aqueous sodium hydroxide solution (i.e. 0.272 kg
or 6.80 mol of NaOH) were added thereto. The reaction
vessel was then opened and the mixture was heated in
stages to 105C, the unreacted dimethylamine being
removed by distillation. The water was removed from the
residual mixture by distillation at a pressure of 6.7
kPa. The distillation residue was cooled to 40C and
mixed with 1.520 kg of methanol, whereupon sodium
chloride precipitated from the mixture. The salt was
removed in a centrifuge, after which the methanol was
2060049
11
recovered from the liquid by di~tillation at a pres~ure
of 6.7 kPa. 1.295 kg (10.86 mol) of 3-dimethylamino-
propane-1,2-diol of boiling point 74 to 75C at 122 Pa
were obtained, i.e. 66.3~ of theory.
