Note: Descriptions are shown in the official language in which they were submitted.
2 ~
HOECHST AKTIENGESELLSCHAFT HOE 89/F 383 Dr. M~/fe
Description
Process for the preparation of 3,4~-dichlorodiphenyl
ether
3,4'-Dichloxodiphenyl ether is an important aromatic
precursor and is used, inter alia, for the preparation of
3,4'-diaminodiphenyl ether, an important raw material for
the synthesis of high modulus aramides, but is also used
as a basic structure for the preparation of plant protec-
tion agents.
~he chlorination of diphenyl ethers, which is carried out
by reaction of diphenyl ether with SO2Cl2 (NL 75~4110 of
18.10.76) in the presence of sulfur-containing catalysts,
does not lead to the desired product, but to 2,4'-di-
chlorodiphenyl ether in addition to 4,4~-dichlorodiphenyl
ether according to the equation
~QJ3c~--t ~
Cl ~ ~ Cl
By skilful choice of the catalyst, it is actually pos-
sible to influence the o/p ratio in the second chlorin-
ation (BE 827,912r US 3,920,757, US 3,793,377; all to Dow
Chemical Co.). However, it is not po sible in this way,
i.e. by direct chlorination, to prepare the desired 3,4'-
dichlorodiphenyl ether.
If the desired product is synthesized by diphenyl ether
synthesis according to Ullmann (Houben-Weyl, Vol. VI/3,
page 86), the following alternatives for the choice of
starting materials results:
2~31 7~
-- 2 --
Cl
~~ ~Cl Cl~O~
Reaction variant 1
OH ~ C1 ~
Cl
~eaction variant 2
1. Reaction of 3-chlorophenol with 1,4 dichlorobenzene
2. Reaction of 4-chlorophenol with 1,3-dichlorobenzene
For reasons of the availability of the starting materials
and the easier distillative separation of unreactad
residues of the starting compounds from the product, the
first variant i5 preferred for industrial production.
Thus, Oshino et al. (JP 62/281,837 of 7.12.1987) react
sodium 4-phenolate, 1,3-dichlorobenzene and aqueous
sodium hydroxide solution, remove water by distillation
and stir in solution (dimethylformamide a the solvent)
with the addition of copper(II) acetate dihydrate at 155-
165C for 18 hours. Nothing is said about working-up:
88.8 % yields are obtained here. Even the stoichiometric
ratios are not clarified.
The di~advantages of this pro~esæ sre, on ~he one hand,
its long reaction period, on the other hand the U8e of
the solvent dimethylformamide which proved to be not very
thermally stable and was therefore largely eliminated
from industrial processes for reasons of the formation of
decomposition products.
In another literature reference, Rauber (US 4,766,253 of
23.8.1988) reacts R-C~H4-OX (X = 1 equivalent of alkali
metal or alkaline earth metal) with an exce~s of 3-15 mol
. !
-- 3 --
of 1,3-C12-C~H4 in the presence of a copper catalyst (in
this case CuO) for several hours at 120-220C (150C in
the example), 0.003-3 mol of an aprotic solvent having to
be present (N,N-dimethylacetamide in the example). An
80 ~ yield of 3,4'-dichlorodiphenyl ether is obtained in
this case after a work-up which is not outlined in more
detail.
In addition to the work-up which is not outlined in more
detail and the moderate yield, this varian~ ha~ the
disadvantage of using an alkali metal or alkaline earth
metal phenolate, which first has ~o be prepared in a pre-
inserted syn~hesis. Industrial production of 3,4' di-
chlorodiphenyl ether - in moderate yield - can only be
carried out poorly economically using this two-step
reaction procedure.
Oshino et al. report in another publication (JP 63/41,434
of 22.2.19~8) another procedure for the preparation of
3,4'-dichlorodiphenyl ether:
sodium 4-chlorophenolate is reacted with 1,3-dichloro-
benzene in liquid aliphatic glycol ethers in the presence
of Cu catalysts to give the desired 3,4'-dichlorodiphenyl
ether. In the example, 4-chlorophenol and 1,3-dichloro~
benzene are reacted with aqueous sodi~m hydroxide solu-
tion to give sodium 4-chlorophenolate, the water of
reaction formed and the water introduced with khe sodium
hydroxide solution being removed by distillation (no
azeotrope).
In the subsequent step, the residue (i.e. nearly all the
water has been removed by distillation) is taken up using
diethylene glycol diethyl ether and reacted at 155-160C
in the presence of Cu(I)Cl for 18 hours in order to
obtain a yield of 87.2 %, it not being certain accoxding
to the description ~ext whether this is an isolated or
chromat~graphically determined yield.
In addition to the long reaction tLme, a disadvantage of
- 4 ~ ~g~
this procedure i~ the use of diglycol dialkyl ethers
which have a relatively low ignition point (under 200~C)
over the whole range and therefore require increased
safety expenditure for industrial production (equipping
the production plant according to EXT4 ), which makes the
plant mor~ expensive, or causes additional costs in an
existing plant. Thus the economically favorable prepaxa-
tion of 3,4'-dichlorodiphenyl ether i~ not possible even
according to this outlined process.
Surprisingly, however, it has become possible a~ a result
of a suitable procedure to achieve an economically and
ecologically favorable preparation process for 3,4'-
dichlorodiphenyl ether based on 4-chlorophenol and 1,3-
dichlorobenzene, i.e. common, industrially ~vailable
starting materials, in the presence of potassium car-
bona~e as an auxiliary base, which saves the entrainment
of large amounts of water-compared to the introduction
of aqueous sodium hydroxide solution - and a suitable
"solubilizer" in the presence of a copper compound as a
catalyst.
The invention thus relates to an improved process for the
preparation of 3,4'-dichlorodiphenyl ether from 1,3-
dichlorobenzene and 4-chlorophenol, which comprises
mixing 1 mol of 4-chlorophenol with about 2 to about
6 mol, preferably about 4 to about 5 mol, of initially
introduced 1,3-dichlorobenzene and about 1 to about
3 mol, preferably about 1 to about 1.5 mol, of pota~sium
carbonate in about 1 to about 5 mol, preferably about 1
to about 2 mol, of a dipolar aprotic solubilizer which
boils above 160C, such as, for example, dimethylacet-
amide, sulfolane, dimethyl sulfoxide, preferably N-
methylpyrrolidone, at temperatures of about 160 to about
190C, preferably about 170 to about 180C, with stir-
ring, then adding about 0.01 to about 1 mol-%, preferably
about 0.1 to about 0.9 mol-% of basic copper carbonate of
the formula Cu(OH)2.CuCO3Ø5 H2O, then heating with
stirring to about 170 to about 173C while removing the
-- 5 --
water formed by distillation, th0n optionally adding
further 4-chlorophenol, with the proviso that from the
start ~he ~moun~ of l,3-dichlorobenzene prasent in terms
of moles is always 1 to 3 mol greater than the totally
added amount of 4-chlorophenol and, if desired, adding
further basic copper carbonate of the formula mentioned,
if at the start less than 0.1 mol-% had ~een added,
additionally stirring within the last-mentioned tempera-
ture range (about 170 to about 173C) and finally working
up after allowing to cool.
The duration of the reaction is about 2-6 hours after
removal of water from the circulation and, in the case of
subsequent addition of 4-chlorophenol, additionally about
2-6 hours more, i.e. a maxLmum of about 4-10 hours.
Working-up after allowing the reaction mixture to cool is
carried out by adjusting the pH to 6 to 6.5 after separa-
ting off the resultant reæidue of the basic copper
carbonate employed and the salts formed, which are
additionally washed with 1,3-dichlorobenzene, and then
working up by distillation.
The procass is expediently carried out at normal pres-
sure. However, it can also be carried out at elevated
pressure if it is carrieA out in the presence of a
dipolar aprotic solubilizer which boils below 160C, such
as, for ex~mple, dimethylformamide.
In addition, the proces~ can be carried out both batch-
wise and also continuously.
In the work-up, the "low-boiling componentæ" ~NNP, 1,3-
dichlorobenzene and 4-chlorophenol) are first removed via
a short column (3-5 plates ? . The desired 3 t 4~-dichloro-
diphenyl ether is then simply distilled over without a
column, a distilled yield of above 90 % being obtained in
very high purity (GC > 99 %).
2 ~
-- 6 --
Three advantages are discernible in the process according
to the invention:
1. As a result of the shor~ reaction period and the
double addition of 4-chlorophenol, the ~pace-time yield
is clearly above those of the known processes outlined
above. The excess of 1,3-dichlorobenzene to 4-chloro-
phenol necessary for the reaction has been en~ured
without having to accept large losses in the space yield.
2. As a result of the outlined distillative work-up, it
is possible to feed back the "low-boiling components"
removed by distillation into the subsequent reactions
again. In this way, the "auxiliary solvent~ N-methyl-
pyrrolidone can be circulated without urther replenish-
ment.
3. As a result of the use of N-methylpyrrolidone as a
dipolar aprotic "solubilizer", a temperature-stable
system having a high ignition temperature and low toxic
potential exists whose industrial availability is guaran-
teed.
Altogether, owing to the use of a suitable "solubilizer",
a suitable copper catalyst and the choice of khe proce-
dure of doubling the addition of the standard component
4-chlorophenol, the process according to the invention i8
an economically and ecologically (by recycling all
components which can be employed again) very favorable
process having a high yield of a highly pure 3,4' di-
chlorodiphenyl ether.
The example below i6 in particular intended to illustrate
the industrial implementation of the proces~ according to
the invention, without restricting the latter thereto~
Example 1
1740 kg of 1,3-dichlorobenzene (10 kmol), 260 kg of
2 ~ t. ~
-- 7
4-chlorophenol (2.023 kmol) and 600 kg of N-methylpyrrol~
idone (231 ~ by weight, based on 4-chlorophenol employed)
are introduced into a 2.5 m3 V4A apparatus fitted with a
stirrer and gas inlet after evacuating and flushing twice
with nitrogen. 310 kg of granulated potas~ium carbonate
(2.246 kmol) and 3 kg (0.013 kmol) of basic copper
carbonate are then additionally added under a weak stream
of nitrogen. The contents of the container are heated to
170-173~C with stirring, water being removed from the
reaction of the phenol with potassium carbonate and the
decomposition of the basic copper carbonate by distil
lation via a splash guard. The reaction mixture is kept
at this temperature with stirring for 3 hours, before 3
kg of basic copper carbonate are first added again and
260 kg (2.023 kmol) of 4-chlorophenol are later 810wly
metered in again as a liquid. The batch is again kept at
170-175C with stirring for 5 hours before it is stirred
until cold to 20-25C.
The solid components of the reaction mixture (potassium
chloride formed and copper oxide from the ca~aly~t) are
removed via a pressure filter washed free of product
using 300 kg of 1,3-dichloroben~ene. The filtrate is
first adjusted to pH 6-6.5 by addition of aqueous 30 %
strength hydrochloric acid, then the water is removed by
distillation via a splash guard up to a transition
temperature of 170C and then introduced into a 3 m3 V4A
still for fractionation via a column containing Sulzer
packing (25-27 theoretical plates).
In this, in a vacuum of initially 20 mbar, the low-
boiling component~ of the reaction mixture are removed bydistillation up to a bottom temperature of 150~C at a
reflux ratio of 1:3, the entire 1,3 dichlorobenzene and
N-methylpyrrolidone as well as unreacted 4-chlorophenol
passing over, and after GC checking of the composition of
the distillate are fed back into the following batch. The
bottom of this fractionation is directly removed from the
V4A apparatus by distillation - without a column - via a
-- 8 --
splash guard. A yield of 880 kg (corresponding to 91 % of
theory, based on ~he amount o~ 4-chlorophenol employed)
of 3,4~-dichlorodiphenyl ether, which has a purity of
> 99 ~ according to GC, is obtained here in the
stationary state.
~ample 2 (comparison example)
1740 g (10 mol) of 1,3-dichlorobenzene, 257 g of 4-
chlorophenol and 310 g o~ potassium carbonate are ini-
tially introduced into a 4 1 four-necked flask fitted
with a stirrer, internal thermometer and heated dropping
funnel, and al80 a ~olid addition funnel, after purging
with nitrogen. The mixture i8 heated to 170-175C with
stirring and kept at this temperature for 10 hours before
the conversion is measured by gas chromatography. A
lS conversion of the components to the desired 3,4'-di-
chlorodiphenyl ether of less than S % (area % of the
analysis) is obtained.
