Note: Descriptions are shown in the official language in which they were submitted.
HOE 74/~ 253 K
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The present invention relates to a process for the pre-
paration of phosphonic and phosphinic acids.
The processes hitherto known for the preparation of phos-
phonic or phosphinic acids from the corresponding alkyl esters
easily obtainable are generally carried out using mineral
acids or hydrogen halides. They have many disad~antages; thus,
they require special methodsfor the purification of the final
product to liberate it from the mineral acids used, or they
cause the formation of considerable amounts of by-products.
Another process is known according to which phosphonic
or phosphinic acid alkyl esters, in the presence of the cor-
responding phosphonic or phosphinic acids, are subjected to
a hydrolytic splitting at temperatures of from 90 to 150C.
The reaction temperatures are expressly limited to a maximum
of 150C, preferably 140C, since only up to these tempera-
tures decomposition and discoloration of the products are avoid-
ed. ~owever, this process so far has not been applied on an
industrial scale since the necessary reaction times are too
long.
Surprisingly, there has now been found a process for
the preparation of phosphonic and/or phosphinic acids by sa-
ponification of the corresponding phosphonic and/or phosphinic
acid alkyl esters, which process overcomes the disadvantages
of the known processes and gives phosphonic and/or phosphinic
acids of excellent quality with practically quantitative yields.
Subject of the present invention is therefore a process
for the preparation of phosphonic and/or phosphinic acids of
the formula ~)
- 2 - `~
HOE 74/F 25~ g
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R1~ ¦¦
~ P - OH (I)
R
were R~ is an alkyl radical having from 1 to 20 carbon atoms,
an alkenyl radical having from 2 to 20 carbon atoms, an ar-
alkyl radical having from 7 to 12 carbon atoms or an aryl ra-
dical having from 6 to 10 carbon atoms, these radicals optio-
nally being mono- to trisubstituted, preferably monosubstitut-
ed, by Cl, Br, alkyl or alkoxy groups each having from 1
to 4 carbon atoms; or R1 is a radical o~ the formula (la)
- Z - P - OX (Ia~
R2
where Z is an alkylene radical having from 2 to 6 carbon
atoms, a phenylene, biphenylene, naphthylene radical or
a radical or the formula (Ib)
Cn H2n ~ Cn H2n (Ib)
where n~ and n2 are identical or different integers of from
1 to 4, preferably n1 = n2 = 1; and R2 in the formulae (I)
and (Ia) is either as defined for R1, except the radical of
formula (Ia), R1 and R2 being either identical or different,
or OH;
by hydrolytic cleavage of phosphonic and/or phosphinic acid
29 alkyl esters of the formula (II)
~OE 74/F 253 K
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R3\11
/ P - oR5 (II)
R4
where R3 is as defined abo~e for R1 except the radical of
f~rmula (Ia), or a radical of the formula (IIa)
_ z - I - oR5 (IIa)
where Z is as defined in formula (Ia) t and R4 in formulae ~II)
and (IIa) is either as defined for R3 except the radical of
formula (IIa), R3 and R4 being either identical or different,
or oR5 or OH, R5 being a methyl group or a straight-chain or
branched alkyl group having from 2 to 8, preferably from 2
to 4 carbon atoms, optionally being substituted, preferably
monosubstituted, by chlorine or bromine;
in the presence of the phosphonic and/or phosphinic acid of
formula (I), which comprises carrying out the hydrolysis at
a temperature of from 170 to 300C, preferably from 190 to
230C, in case of R5 being a methyl group at a temperature
of from 160 to 250C, preferably from 170 to 190C, with
the use of at least a stoichiometric amount of water, and by
distilling off the alkanol formed, optionally together with
water.
The process of the in~ention is generally carried out as
follows: the ester of formula (II) and from 2 to 30 weight %,
preferably from 5 to 20 weight ~, relati~e to the ester, of
29 the corresponding acid of formula (I) are heated to the desir-
-- 4 --
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ed reaction temperature, and then the water is added in such
a manner that the reaction temperature is maintained. Also
alkanol containing water may be used for the hydrolysis. A
good intermixing of the reactants is recommended.
OE course, the reaction mixture and the water may be
heated simultaneously to reaction temperature with water op-
tionally distilling off, and the water still required after hav-
ing attained the reaction temperature may be added as indicat-
ed above. It is also possible to heat the ester of formula
(II) alone to reaction temperature and to add subsequently a
solution of the desired amount of acid of formula (I) in the
required amount of water. In case of the methyl ester of
formula (II), the required amount of water may be added alone,
provided that a certain induction time is taken into considera-
tion which is due to the fact that the amount of catalytically
actLve acid of formula (I) necessary for a rapid course of the
rea tion is formed from the ester by hydrolysis only then.
The upper limit of the acid/ester ratio is set only by econo-
mic considerations; anyhow it rises towards infinity with the
hydrolgsis proceeding.
According to the process of the invention, the alkanol
formed in the reaction is distilled off, preferably in usual
manner via a distillation column or an equivalent device, option-
ally in the form of an azeotropic mixture; entrained water
which possibly separates in the condensation ofthe azeotropic
mixture being eliminated and recycled into the hydrolysis.
As stoichiometric amount, there is required 1 mol of water
for each ester group of the compound of formula (II). General-
29 ly, however, it is advantageous to use an excess of water,
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which depends above all on the efficiency of the device used
for separating the alkanol and on the amount of water entrain-
ed by the azeotropic mixture. On the avera~e, in the case
of industrial equipment, a water excess of from 50 to 200%,
and from 10 to 50% when using the methyl ester of formula (II),
above the stoichiometric amount is used. In order to accele-
rate the hydrolysi~ and to complete it more rapidly, it may
be advantageous to add lar~e amounts of water towards the end
of the hydrolysis, so that the excess may amount to 200% and
more, and up to 100% when the methyl ester of formula (II) is
used. The alkanol containing water obtained may be reused for
a further hydrolysis. Water excesses of more than 100% or
even 200~, for example up to 300~ or more may be used with-
out adversely affecting the process, but they are disadvan-
tageous because the alkanol contained in the excess water,
for reasons of preventing pollution, would have to be eli-
minated by distillation.
The pressure to be chosen for the process of the invention
is not critical, but the process is preferably carried out
under atmospheric pressure. ~owever, any other pressure,
especially elevated pressure, may also be applied, preferably
a pressure below the vapor pressure of the water and/or the
alkanol at reaction temperature.
By adding a quantity of water below the stoichiometric
amount, it is possible to attain a partial hydrolysis only,
so that mixtures of esters, semi-esters and/or acids are
obtained.
The process may be carried out batchwise or continuously.
29 ~ The reaction temperatures are from 170 to ~00 C, prefer-
HOE 74/F 253 K
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ably from 190 to 230C, or from 160 to 250C, preferably
from 170 to 190C when the methyl ester of formula (II) is us-
ed; the reaction temperatures required rising towards the up-
per limit of the intervals with increasing number of carbon
atoms in the radicals Ri to R~.
Of course, the hydrolysis of the esters of formula (II)
according to the process of the invention may be carried out
also in the presence of other acidic catalysts, for example
sulfuric or p-toluenesulfonic acid. Thus, the hydrolysis of
an ester of formula (II) may be started also in the absence
of an acid of formula (I), by adding first small amounts,
that i~, preferably from 2 to 10 mol ~, relative to the
ester of formula (II), of aqueous or gaseous HCl at reaction
temperature, so that the amount of phosphonic or phosphinic
acid desired for continuing the hydrolysis is produced in situ.
How?ver, the formation of the corresponding alkane chloride
mus~ be taken into consideration in this case. When the methyl
esters of formula (II) are used, the hydrolysis starts at re-
action temperature by adding water alone. However, an espe-
cially advantageous embodiment of the process of the invention
is based on avoiding the use of catalysts foreign to the system,
thus allowing the obtention of the desired final products in
pure form and practically free from water. Contrary to the
teaching of the state of the art, at the elevated temperatures
of the process of the invention at which the reaction mixture
cannot but dissolve small amounts of water, the hydrolysis
proceeds not only with considerably increased reaction speed,
but also decomposition and discoloration as described in the
29 literature are not observed.
_0 ~ 3 F.
1043;~S0
This result is ~ery surprising, especially in the case of
high molecular weight products. It is also surprising that
at the reaction temperatures according to the invention prac-
tically no pyrophosphonic acids or anhydrides are formed and
also dialkyl ethers or alkenes are formed to an insignifi-
cant extent only or not at all.
As starting products of fDrmula (II~, phosphonic acid
dialkyl or monoalkyl este~,phosp~linic acid alkyl esters and
biphosphonic and biphosphinic acid alkyl esters are used,
such as the dimethyl esters of ethanephosphonic acid, pro-
panephosphonic acid, hexanephosphonic acid, octanephosphonic
acid, hexadecanephosphonic acid, chloromethanephosphonic
acid, p-bromobenzenephosphonic acid, the methyl esters of
ocatanephosphon~c acid, methylethylphosphinic acid, methyl-
octylphosphinic acid, methylvinylphosphinic acid, the di-
me~hyl esters of ethane-1,2-bis-methylphosphinic acid, phenyl-
ene-1,4-bis-methylphosphinic acid, benzylphosphonic acid,
methylbenzylphosphinic acid methyl ester, eicosanephosphonic
acid dimethyl ester, the methyl esters of methyleicosylphos-
phinic or methylphenylphosphinic acid, the diethyl, dipropyl,
di-n-butyl, diisobutyl, dioctyl ester of ethanephosphonic
acid, the diisobutyl esters of propanephosphonic acid and
octanephosphonic acid, hexanephosphonic acid diisopropyl
ester, octanephosphonic di-(2-ethyl-hexyl) ester, hexade-
canephosphonic acid diethyl ester, chloromethanephosphonic
acid isobutyl ester, p-bromobenzenephosphonic acid diethyl
ester, octanephosphonic acid isobutyl ester, methylethyl-
phosphinic acid ethyl ester and -isobutyl ester, methyloctyl-
29 phosphinic acid isobutyl ester and -(2-ethylhexyl) ester, the
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isobutyl esters of methylvinylphosphinic acid, ethane-1,2-
bis-methylphosphinic acid and phenylene-1,4-bis-methylphos-
phinic acid, benzylphosphonic acid diethyl ester, the iso-
butyl esters of methylbenzylphosphinic acid and methylphenyl-
phosphinic acid.
Mixtures of the corresponding mono- and dialkyl esters
may also be used.
Preferred radicals R1 or R2 which according to formula
(I) are lir~ed to the phosphorus via a direct C - P ~ond are
those containing from 1 to 16, especially from 4 to ~2 car-
bon atoms.
It is recommended to carry out the hydrolysis, especial-
ly at the beginning of the reactior., in an inert gas atmos-
phere. As inert gases, there may be used for example nitro-
gen or argon or C02. The reaction may also be carried out
in the presence of a high-boiling inert solvent such as o-di-
chlorobenzene, dichlorotoluene, mono- or dichloroxylene.
After complete reaction, the phosphonic and phosph~nic
acids obtained as crude products may be purified according to
known methods; phosphonic scids may for example be recrystal-
lized, phosphinic acids distilled.
Phosphonic and phosphinic acids are interesting inter-
mediate products, for example for the preparation of plant
protection products. Furthermore, they may be used, option-
ally also in the form of their salts, as textile auxiliaries,
antistatic or flame retarding agents, solutes, anti corro-
sion or flotation auxiliaires.
- The following examples illustrate the invention.
HOE ~/F 25~ K
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E X A M P ~ E 1:
154 g of chloromethanephosphonic acid dimethyl ester and
15.4 g of chlorome-thanephosphonic acid are heated to 165 -
170C. Subsequently, with thorough agitation, a total of
70 ml of water is added dropwise within 4 hours. Methanol and
water are distilled off via a distillation column. In a sub-
sequent cooling trap, 11 g of dimethyl ether are collected,
~hich amount corresponds to about 25 mol ~, relative to the
methanol amount theoretically obtained in the hydrolysis. The
residue is 142.5 g of chloromethanephosphonic acid, correspond-
ing to a yield of 100~ of the theoretical yield .
E X A M P ~ E 2:
224 g of hexadecanephosphonic acid dimethyl ester and
22.5 g of hexadecanephosphonic acid are heated to 190 - 200C
under a nitrogen atmosphere. Subsequently, with vigorous
agi-~ation, a total of 80 ml of water is added dropwise with-
in 5 hours. A methanol/water mixture is distilled off via a
dis-tillation column, which mixture contains 38 g of methanol
(90~ of the theoretical amount). In a subsequent cooling trap,
a small amount of dimethyl ether is collected. The residue is
227.5 g of hexadecanephosphonic acid, solidification point
about 85C, which corresponds to a 100~ yield.
E X A M P ~ E 3:
300 g of octanephosphonic acid dimethyl ester and 30 g of
octanephosphonic acid are heated to 180 - 190C under a nitro~
gen atmosphere. -Subsequently, with vigorous agitation, 60
ml of water are added dropwise within 2 hours. ~he methanol
formed is distilled off via a distillation column. In a sub-
29 sequent cooling trap, 3 g of dimethyl ether are collected,
-- 10 --
HOE 74/F 253 K
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which corresponds to about 5 mol %, relative to the methanol
amount theoretically obtained in the hydrolysis. The residue
is 292 g of octanephosphonic acid, solidification point
81C, which corresponds to a yield of 100%.
wnen the same reaction is carried oui at 20ûC, the re-
action time is 1.5 hours.
E X A M P ~ E 4:
65 g of benzenephosphonic acid dimethyl ester and 6.5 g
of benzenephosphonic acid are heated to 180C. Subsequently,
wlth vigorous agitation, 13 ml of water are added dropwise
within 5 hours. The methanol formed in the reaction is distil-
led off via a distillation column. In a subsequent cooling
trap, 3.3 g of dimethyl ether are collected, which corre-
sponds to about 20 mol %, relative to the methanol amount
theoretically obtained in the hydrolysis. The residue cry-
stallizes and is 61.6 g of benzenephosphonic acid, melting
po:int 158 - 160C, which corresponds to a yield of 100~.
E ~ A M P ~ E 5:
61 g of methylethylphosphinic acid methyl ester and 6.1 g
of methylethylphosphinic acid are heated to 180C. Subse-
quently, with vigorous agitation, 10 ml of water are added
dropwise within 6.5 hours. The methanol formed in the re-
action is distilled off via a column. In a subsequent cool-
ing trap, 1 g of dimethyl ether is collected, which corre-
sponds to about 9 mol %, relati~e to the methanol amount
theoretically obtained in the hydrolysis. The residue ~s 60 g
of methyethylphosphinic acid (boiling point at 0.7 mm HG:
130 - 132C), which corresponds to a yield of 100~.
- 11 - ,
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E X A M P ~ E 6:
.
26.2 g of phenylene-1,4-bis-methylphosphinic acid methyl
ester, 2.6 g of phenylene-1,4-bis-methylphospinic acid and
10 ml of o-dichlorobenzene are heated to 180C.. Subsequently,
with vlgorous agitation, 4 ml of water are adaed dropwise
within 6 hours. The methanol formed in the reaction is distil-
led off via a column. In a subsequent cooling trap, a very
small amount of dimethyl ether is collected. Subsequently,
the dichlorobensene is distilled off in a water-jet vacuum.
26 g of phen~lene-1,4-bis-methylphosphinic acid, melting
point 230C, are obtained, which corresponds to a 100~ yield.
E X A M P ~ E 7:
276 g of ethanephosphonic acid dimethyl ester are heated
to 180C. Subsequently, with vigorous agitation, 80 ml of
water are added dropwise within 10 hours. The methanol formed
in the reaction is distilled off ~ia olumn. In a subsequent
co;~ling trap, some dimethyl ether is collected. The residue
is 220 g of ethanephosphonic acid, which corresponds to a
yield of 100%.
E X A M P ~ E 8:
125 g of butanephosphonic acid di-n-butyl ester and 35 g
of butanephosphonic acid are heated to 200C. Subsequently,
with vigorous agitation, a total of 60 ml of water is added
dropwise within 4.5 hours. The n-butanol and excess water
are distilled off via a distillation column. In a subsequent
cooling trap, 3 g of butylene are collected, which corre-
sponds to about 5.5 mol ~, relative to the butanol amount
theoretically obtained in the hydrolysis. The oily residue
29 is~104 g of n-butanephosphonic acid, corresponding to a 100
HOE 74/F 253 K
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yield.
E X A M P ~ E 9:
._
300 g of methyloctylphosphinic acid is~butyl ester and
30 g of methyloctylphosphinic acid are heated to 200 - 220C.
~ubsequently~ with vigorous agitation, 40 ~i Ol wa~er a;e
added dropwise within 10 hours. The isobutanol and water are
distilled off via a distillation column. In the distillate,
isobutanol containing water separates as lower phase and is
recycled into the reaction process. In a cooling trap, 2 g
of isobutylene are collected, which corresponds to about 3
mol %, relative to the isobutanol amount theoretically ob-
tained in the hydrolysis. The residue solidifies. 262 g of
methyloctylphosphinic acid, solidifaction point 42.5C, are
obtained, corresponding to a yield of 100~.
E X A M P ~ E 10:
1015 g of methylethylphosphinic acid isobutyl ester are
cc~bined with 10 ml of concentrated hydrochloric acid, and
with vigorous nitrogen f1ushing, the mixture is heated to
190 - 200C. At this temperature, the flushing is stopped.
Subsequently, with vigorous agitation, a total of 250 ml
of water is added dropwise within 12 hours. Isobutanol and
water are distilled off via a distillation column. In the
distillatelisobutanol containing water separates as lower
phase and is recycled into the reaction process. In a cool-
ing trap, 15 g of isobutylene are collected, corresponding
to about 4.5 mol %, relative to the isobtanol amount theore-
tically obtained in the hydrolysis. The residue is 668 g of
methylethylphosphinic acid, boiling point at 0.7 mm Hg 130 -
29 132 C, which corresponds to a yield of 100%.
- 13 -
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E X A M P ~ E 11:
300 g of octanephosphonic acid diethyl ester Pnd 30 g of
octanephosphonic acid are heated to 190 - 200C. Subsequently,
with vigorous agitation, 160 ml o~ water are added dropwise
within 5 hours. 158 g of water containing ethanol (water con-
tent 34.3%) are distilled off via a distillation column, cor-
responding to a yield of 95% of ethanol. The residue solidi-
fies. 263 g of octanephosphonic acid, solidification point
about 85C, are obtained, corresponding to yield of 100%.
E X A M P ~ E 12:
600 g of octanephosphonic acid di-isobutyl ester and 60 g
of octanephosphonic acid are heated to 195 - 200C with nitro-
gen flushing, which is stopped at this temperature. Subse-
quently, with vigorous agitation, 260 ml of water are added
dropwise within 5 hours. Isobutanol and water are distilled
off via a distillation column. In a subsequent cooling trap,
41 g of isobutylene are collected, which corresponds to about
18.5 mol %, relative to the isobutanol amount theoretically
obtained in the hydrolysis. The residue solidifies. 440 g
of octanephosphonic acid, solidification point about 85C,
are obtained, corresponding to a 100~ yield.
- 14 -
