Note: Descriptions are shown in the official language in which they were submitted.
~41~Q43
H 1112
In making esters of phosphoric acid, phosp~orous
acid, alkane or arylphosphonous acids, alkane or aryl-
- phosphinic acids and alkyl or arylphosphonic acids, it
is good practice to use the corresponding acid halides,
e.g. the chlorides, as starting material.
- It ~s known that those esters can be made ~ro~
phosphoric acid halides by reactir,~ them with alcohols.
For example, it is possible to produce phosphorous
acid dialkylesters by reacting PCl3 with e~uimolar
praportions of an alcohol in accordance with the
~ollowing equation (1):
(1) PCl3 ~ 3 ROH ~ -> (RO)2P + RCl ~ 2 HCl-
- \ H
(Houben-W~ l, "Methoden der Organischen Chemie",
, ~
volume i~t~-, (1964~, Pages 21-28).
Symmetrical phosphoric acid triesters can be
produced as shown by the following equation (2)
(2) POC13 + 3 ROH ----- > (RO) PO + 3 HCl
.
~H~ ben-Weyl, "Methoden der Organischen Chemie", volume
(1964), pages 310-315).
arc~Phos~o c~r
Monoesters of alkane or ~ acids can also
be made by reacting the corresponding alkyl or aryl-
chlorophosphines with alcohols in accordance with
eQu~tion (3) ~ ~~
', .
.' ._, ..... ' . ~ ~ .
~)4~{~43
11 .
(3) R-PCl2 ~ 2 R'OH~R-IP-H -~ HCl + R'Cl
OR'
(Houben-Weyl7 "Methoden der Organischen Chemie", volume
~2/1 (1963), pages 320-323),
Diesters of alkane or arylphosphonic acids can be
made as shown by equation (4):
11
(4) R-POCl2 + 2 HO-R' -~R-P(OR')2 + 2 HCl
(Houben-Weyl, "Methoden der Organischen Chemie", volume
12/1, (1963), pages 423-430).
Es-ters of dialkyl, diaryl or arylalkylphosphinic
acids are obtainable by reacting the corresponding acid
chlorides with alcohols in accordance with equation (5):
.
(5) RzP(O)Cl + R~ok~ R2P(O)OR' + HCl
. . :
(Houben-Weyl, i'Methoden der Organischen Chemie", volume
12/1, (1963), pàges 248-249).
As descrlbed in the art, it is customary for
phosphorus-containing esters to be produced at low
temperatures, commonly in the presence of bases
sequesterirlg the resulting hydrogen chloride~. This is
more-particularly true concerning reactions, wherein
PC13 and R-PCl2 are used as the starting materials. me
bases used therein include amnmonia and organic nitrogen
bases, such as amines or pyridines. The use OI inert
solvents is also typical of the processes described
-- 3 -- --
.
'~ .
~L~4~3
heretofore. During manufacture, it is necessary for base
hydrochloride to be filtered off and for the inert
solvent to be separated. After this has been done, the
phosphorus-containing ester can be obtained, commonly
by distillative treatment. The prior processes for
making phosphorus-containing esters are rendered costly
and difficult by the facts that they are carried out at
low temperatures within the range -30 and +20C with
the use of inert solvents and bases sequestering the
hydrogen chloride, and that it is necessary for the
base hydrochloride to be filtered off from the reaction
mixture.
The present invention now provides a process
for making phosphorus-containing esters of the general
formula:
o
X-P-Z,
y
in which X stands for an alkyl group having from 1 to
3 carbon atoms, an aryl group or an alkoxy group having
from 1 to 6 carbon atoms, Y stands for an alkoxy group
having from 1 to 6 carbon atoms, and Z stands for a
hydrogen atom, an alkyl group having from 1 to 3 carbon
atoms or an aryl group, by reacting one or more phosphorus
halides of the general formula:
A-P-C,
D
3043
in which A and B stand independently from one another
for a chlorine or bromine atom, an alkyl group having
from 1 to 3 carbon atoms or an aryl group, C stands for
a chlorine or bromine atom and D stands for a free pair
of electrons or an oxygen atom, with aliphatic alcohols
having from l to 6 carbon atoms, which process comprises
heating to boiling, in a reaction zone, the phosphorus
halide and the aliphatic alcohol at temperatures within
the range 60 and 150C, passing the resulting hydrogen
halide and alchol in excess to the upper portion of the
reaction zone, condensing it therein and removing it
therefrom; and flowing resulting phosphorus-containing
ester, if desired with an excess of aliphatic alcohol,
to the lower portion of the reaction zone and removing
it therefrom.
The phosphorus halide compounds which may be
used in the present process include, for example: phos-
phorus trichloride, ~ethyldichlorophosphineg ethyldichloro-
phosphine, propyldichlorophosphine, phenyldichlorophos-
phine, phosphorus oxychloride, methanephosphonic acid
dichloride, ethanephosphonic acid dichloride, propanphos-
phonic acid dichloride, phenylphosphonic acid dichloride,
dimethylphosphinic acid chloride, dipropylphosphinic acid
chloride, methylethylphosphinic acid chloride, methyl-
propylphosphinic acid chloride, ethylpropylphosphinic
acid chloride and the corresponding bromides.
Useful alcohols are, for example, methanol,
ethanol, n-propanol, i-propanol, n-butanol and similar
alcohols, isobutanol being particularly preferred.
It is very advantageous to effec~ the reaction
8~
in the presence of nitrogen, argon or carbon dioxide
as an inert gas. The reaction zone should pre~erably
be supplied continuously, per mol of phosphorus halide,
~with 1.2 -to ~ times -the s-toechiome-tric quantity of
alcohol, the quantity of alcohol~ which is introduced
once into the reac-tion zone to initiate the reaction,
being ignored. The alcohols should preferably contain
less than 0.5 weigh-t /0, more preferably less than 0.1
weight %, o~ water.
It is preferable for the reaction to be effected
at temperatures close to the boiling point to the
mixture of alcohol and resulting phosphorus-
containing es-ter, i.e. at temperatures wi-thin the
range 78 and 110C, if ethanol is used, or a-t
temperatures within the range 108 and i40C, if lSO-
bu-tanol is used.
It is even more preferable for the reac-tion to be
e~fected in the following manner: phosphorus halide and
aliphatic alcohol in liquid or vapor form are supplied
continuously, in the molar ratio indicated hereinabove,
to a reaction zone, e.g. a column, heated to boiling
therein, whereby the resulting hydroge~ halide and a
portion of the boiling alcohol are delivered to the
upper portion of the zone, in which they are distilled,
continuously condensed and removed therefrom9 whereas
the resulting phosphorus-containing ester, which is
the higher boiling ingredient of the mixture, is
delivered3 if desired together with a portion of boiling
a1~ohol, to the lower portion of the zone and ;
continuously removed therefrom.
- ` - 6
1~481V43: . :
The react.ion products are worked up inknown manner,
It is possible for the phosphorus-containing ester to be
freed distilla-tlvely from aliphatlc alcohol in excess, if
'desired a~ter neu-tralization of the solution.The distillate '
consisting of hydrogen halide, aliphatic alcohol and alkyl
halide, if any, which lS removed from the upper~portion 'of ~
the reaction zone, is also separated by conventional ' ' '
- methods and the alcohol is rècovered there~rom.
~,
' The process of the present inven-tion unexpectedly
enables the dçcomposition of the resultlng phosphorus- '~
'containing ester by hydrogen halide, which is formed
thereinj to be substantially lnhibited. This is due to
' the fact that the reaction heat which is set free upon
,
the reaction of the phosphorus halide wlth the aliphatic
alcohol~ makes it impossible for the hydrogen halide to
. .
remain in contact for some prolonged time with the
~ resulting phosphorus-containing ester. The hydrogen
- ~ hallde rather escapes at once lnto the upper portion of
the reaction zone and is thus separated from the ~ -
phosphorus-containing ester which in turn, as the '
; higher-boillng component, is delivered to the lower~
.- ' portion o~ the reaction 20ne.
' m e process of the present inventlon compares~
' favorably with the prior art in various respècts~
- The phosphorus-containing'ester is separated ver~
rapidly and in a manner which is typical of the present
process ~rom hydrogen halide which'is formed
slmultaneously ~~erewith. In other words, the~hydrogen
.' halide is considerably less likely to catalyze th~e~ 'S`!^`';
: 30 decomposltion o~ the phosphorus-containing ester~
which is accordingiy obtained in improved yields. In
the prior art processes, it is necessary to use bases,
such as ammonia or organic amines, ~or sequestering
all the hydrogen halide in the form of ammonium or
amine hydrohalide salts, which precipitate and are
filtered off with heavy loss o~ material. A portion o~
the base hydrohalides remains, however, dissolved and
ef~ects the catalytic decomposition of the phosphorus-
containing es-ters, whereby the yield is impaired~ These
are disadvantageous effects which are not encountered
in the process o~ the present invention. The phosphorus-
containing esters are obtained in more concentrated form
than in all prior art processes. The heat, which is set
~ree on reacting the phosphorus halides with aliphatic
alcohols -- this being an exothermal reaction -- at the
boiling poin-t of the mix-ture, is dissipated by~"vapor
cooling" and the hydrogen halide is removed jointly
therewith. In prior art processes, wherein the reactio~
is effected stagewise, such heat is required to be
dissipated through the reactor wall so as to permit
hydrogen halide~ which is retained in the solution, to
be neutralized in an equally highly exo-thermal reaction,
and thereafter to be dissipated once again through the
reactor wall, this time in a liquid medium which becomes
increasingly more viscous by solid base hydrohalide,
which precipitates therein.
In those prior processes which are carried out,
e.g. with the use o~ an ammonia base and a chlorine-
containing compound, it is additionally necessary for
precipi;ated microcrystalline ammonium chloride to be
- 8 ~
'., : ''
.. . ~ ~,
~f~14~3~4;~
stirred for some hGurs in the reaction medium to effect
recrystallization of the salt and its transfor,mation
into fil-terable material. The capaci-ty of the apparatus
is substantially a ma-tter of,indifference in the '
commercial process of the present invention which
provides for an uninterrupted delivery of starting ' ' ~'
material to~ and removal of flnal product from, the
reaction zone. Thls is in clear con-trast with the known
preparation in stages producing limited space~time-
yields, which are criti,cally affected by the ,cooling , ;'
area of the reactor, In additlon to this, stagewise ~ -
operation is rendered very expenslve by the need to
appropriately dimension'-the apparatus for filtering ' ~ ;
the base hydrohalide.
Phosphorus-containing esters having P-H bonds
thereln are very,useful starting materials for making ',
~lameproofing agents for polyesters, polyurethanes and
polyacrylonitrile. Theseare very pure and accordingly
well adapted for use in reac-tions which are catalyzed ' -~
by radical yLelding agents.
'~ . . , ' : ' ' ~'~
EXAMPLE 1~
- ~Methanephosphonous acid isobutylester; cf.
' equation ~3
', An apparatus such as that shown in the accompanying
drawing was usèd. 900 ml (722 g =' ~ mol) of iso~
- , : ~ : .
butanol was so introduced into circulation evaporator ,~
(1) and heated t~ boiling -therein while nitrogen~was
supplied a-t a ra~e of 2 - 3 l/h t~at the boiling
temperature of 1~8C was reached near the head of
~IL63 9~8~L3
column (2), below cooler (3). At that temperature, 130
g/h (1.~1 mol) of methyldichlorophosphine i~ vapor form
was introduced approximately in-to the center portion of
column (2), through inlet (10) and preheater (8). 292
g/h (3.95 mols) of iso-butanol, which was partially in
vapor form and partially in liquid form, was introduced
into column (2) substantially at the same level, through
inle-t (11) and preheater (9). The temperature in the~
circulation evaporator (1) increased from 108 to 135C
and was 110C in the column base portion. In the center~ -
portion of the column, where the reaction took place,
the temperature was between 97 and 112C, and it dropped
to 95C during the reac-tion, near the head of the -~
column. A mixture of iso-butanol, iso-bu-tylchloride and
hydrogen chloride distilled off near the head of the
column, through line (4). Reaction product was~removed
continuously from the circulation evapora-tor (1), once
the temperature was at 135C therein, through line (7).
Altogether 4.22 mols of methyldichlorophosphine and
15 mols o~ iso-butanol were supplied within 3.8 hours.
The experiment was interrupted, the material in the
column base (altogether 959 g) was remo~ed co~pletely
and the reactlon product was subjected to gas chromato-
graphy. It contained 58.2 weight % (55~ g = 4.1 mols)
of methanephosphonous acid monoisobutyl ester ~97.2 %
o~ the theoretical)~ The distillate in recelver~(5) `~;
contained 3.59 mols of hydrogen chloride. A further
0.63 mol of HCl was in an off-gas scrubber ~6~, placed
downstream of receiver (5)~ wherein the off-gas was0 scrubbed with water. The distillate obtained near the
`
- 10 -
'~
-
43
head of the column could not be found -to contain
methanephosphonous acid monoisobutyl ester or diiso-
butylester. The p~osphorus content was 0.03 weight %.
EXAMPLE 2: (Comparative Example)
A solution of 58.5 g (0.5 mol) of methyldichloro-
phosphine in 300 ml of anhydrous ether was admixed
dropwise under nitrogen, with agitation and while
coollng, with 88.8 g (1.2 mol) of iso-butanol and 50.5 g
10:~ (0.5 mol) of triethylamine in 100 ml of anhydrous ether.
The whole was reflux-heated for 30 minu-tes at 35C,
- then cooled down to 5C and fil-tered. The filtrate was
concentrated and vacuum-distilled under nitrogen. Iso-
butanol and iso-butyl chloride in excess were remo~ed
together with the first runnings. 59.8 g (0.44 mol~ of
methanephosphonous acid isobutylester (88 %~of~the
theoretical) was obtained as the main produc-t.
. ' --
EX~MPLE 3: ~Comparative Example)
20 ~ A rea¢tion flask was fed with 2220 g (30 mols) of
iso-butanol which was admixed dropwise within Z hours ;
under nitrogen, with agitation and while cooling down
to less than 20C, with 585 g ~5 mols) of methyl-
dichlorcphosphine-.
The whole was neutralized for 3 hours wlth gaseous~
- ammonia with agitation and while cooling down to less
- than 30~:C. Agitation was continued for about a further
8 hours to effect recrystallization of the ammonium
chlor:ide which was suction~filtèred. The filter cake
was washed twice~ each time with 200 g of iso-butanol.
~04~3
The filtrate (3220 g) was subjec-ted -to gas chromatog.raphy
and ~ound to contain 19.2 % (615 g = 4.52 mol) of
methan0phosphonous acid isobu-tyles-ter ~90.5 % of the
theoretical).
EXAMPLE 4: (Diisobu-tylphosphite; cf. equation (1))
Column (2) was supplied with 900 ml o~ iso-butanol
and 157 g/h (1.14 mol) of phosphorus trichloride and
386 g/h (5.22 mo.ls) o~ iso-bu*anol were added thereto,
in the manner described in Example 1. Reaction product
was removed continuously from the circulationevaporator
(1) through line .(7), at a temperature of 135C in the . . .
column base portion. The temperature at -the head of
the column dropped from 108C down to 84C. After 3
hours~ -the experiment was interrupted, the column base.
was freed completely from the material therein (altogether
874 g~ and the material was subjected to gas chromato-
gr.aphy. The specimen tested contained 71.6 weight %
(626 g = 3.23 mols) o~ diisobutyl phosphite (94.4 % of
the theoretical). The head distilla-te (receiver 5)
contained 3.84 mols of hydrogen chloride and a ~urther
2..96 mols o~ hydrogen chloride was in the off-gas
~crùbber(6) placed downstream thereof. ~:
. ~
- EXAMPLE
-~ . . (Methanephosphonic acid diisobutylester; c~
equation (4)). . -~
Column (2) ~ras supplied with 900 ml of iso-bu-tano]., ..
~hich was heated to boilin~ ~therein and then admixed, in
the manner described in Example 1, with 144 g/h (i.08 mols)
.
.
. - - , . ~ :
. . -' -` .,
4;3
of me-thanephosphonic acid dichloride (in liquid preheated
form) and with 304 g/h (4.10 mols) of iso-butanol. me
reaction pro~uct was removed -through line (7) at a
temperature of 132C in the column base portion. The
temperature near the head of the column dropped from
108C down to ~1C. Altagether 4.24 mols of methane-
phosphonic acid dichloride were introduced, the experiment
was interrupted, the material in the column base portion
was comple-tely removed therefrom (1083 g) and subjec-ted
to gas chromatography. The specimen tested contained
72.7 weight % (787 g = 3.79 mols) of methanephosphonic '~~
acid dibutylester. The yield was 89.3 % of the theore-
-tical. The head product (receiver 5) contained 5.Z4 mols
of hydrogen chloride and the off-gas scrubber (6) placed
downstream thereof contained 2.~5 mols of hydrogen
chloride.
EXAMPLE 6:
~Methanephosphonous acid ethylester; cf.equation (3)).
Column (2) was supplied, in the manner described in
Example 1, with 900 ml (710 g - 15.4 mols) of ethanol which
was admixed with 130 g/h ~1.11 mols) of methyldichloro-
., . . ~ ,.
phosphine and 187 g/h (4.05 mols~ of ethanol. Altogether
; 2.11 mols of methyldichlorophosphine was introduced, the
experiment was in-terrupted and the material in the~column
base portion t401 g) was completely removed therefrom,
once the temperature was at 83C. It was subjected to
gas chromatography and found to co~tain 31.5 welght %
(126.3 g = 1.17 mols) of methanephosphonous acid mono-
ethylester (55 ~ % of the theoretical).
, . . . .
