CA1050562A

CA1050562A - Production of phosphorus-containing esters

Info

Publication number: CA1050562A
Application number: CA249,987A
Authority: CA
Inventors: Horst Staendeke; Elmar Lohmar
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1975-04-30
Filing date: 1976-04-09
Publication date: 1979-03-13
Also published as: DE2519192A1; IT1061688B; NL7604373A; NL183401C; JPS51136624A; BE841273A; NL183401B; DK191976A; FR2309563A1; ATA310776A; JPS5926633B2; CH612944A5; SE7602715L; GB1490835A; AT340949B; DD125691A5; SE424639B; FR2309563B1; DE2519192C2

Abstract

ABSTRACT OF THE DISCLOSURE

Production of phosphorus-containing esters of the general formula in which X stands for an alkyl group having from 1 to 3 carbon atoms, an aryl group or an alkoxy group having from 3 to 6 carbon atoms, Y stands for an alkoxy group having from 3 to 5 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 phosphohalogen compounds of the general formula in which A and B each stand independently of 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 3 to 6 carbon atoms.
The phosphorus-containing esters are made by mixing and thereby reacting in an unheated reaction zone in liquid phase the phosphohalogen compound with the aliphatic alcohol and delivering the resulting reaction mixture to the head of a steam-heated packed column; feeding the column's base portion with inert gas travelling upwardly therein countercurrently with respect to the reaction mixture; distilling off overhead hydrogen halide, alcohol in excess and, alkyl halide, if any, together with the inert gas; partially condensing and removing the distilled matter; and removing resulting phosphorus-containing ester flowing downwardly in the column from the column head to the column base, from the column base portion, if ?sired in admixture with alcohol in excess.

Description

50 5~'~
- ~ 1160 .
--- Esters o~ phosphorous acid, allcane or aryl phosphonous acids, alkane or aryl phosphonic acids and dlalkyl or diaryl phosphinic acids are conveniÆn-tly made by reac-ting a sui-table acid halide, e.g. a chloride, with an alcohol.
Phosphorous acid dialkylesters are obtainable fro~
PCl3 by reac-ting it with an equimolar proportion of an alcohol in accordance with equation (1) ' O .-PC13 + 3 RO~I (R)2P \ + RCl ~ 2 ~Cl : H
(Houben-Weyl~ Methoden der Organischen Chemie 7 vol. 12/2, &. Thieme-Verlag (Stuttgart) 1964, pages 21-28, and G.M.
Kosolapoff and L. Maier, Org~nic Phosphoru6 Compoun~s, vol. 5, Wiley-Interscience (New York) 1973).
` Monoesters of alkane or aryl phosphonous acids can be obtained by reacting a suitable alkyl or arylchloro-. phosphine with an alcohol in accordance with equation ~2) - - O

R-PCl2 + 2 R'OH ~ R-P-H + HCl -~ R'Cl OR' (Houben-Weyl, Methoden der Organischen Chemie, vol. 12/1, G. Thieme-Verlag (S-tuttgart) 1963, pages 320-323, and G.M. Kosolapo~f and L. Maier, Organic Phosphorus Compounds, vol. 4, Wiley-Interscience (New York) 1972).
Diesters of alkane or aryl phosphonic acids are ; obtainable in accordance with equation (3) . . O
R-P~O)Cl2 ~ 2 R'OH ~ R-P(OR')2 + 2 HCl -: 2 .

,, , .. .. _ ~ 5~ Z
tHouben-Weyl 9 Methoden der Organischen Chemie, vol.12/1 7 G. Thleme-Verlag (Stuttgart) 1963, pages 423-430).
Esters of dialkyl, diaryl or aryl-alkyl phosphinic acid can be made by reacting a suitab]e acid chloride ~ith an alcohol in accordance with equation (4) R2P(O)Cl ~ R'OH--------------------~R2P(O)OR' ~ HCl (Houben-Weyl9 Methoden der Organischen Chemie, vol. 12/1, G. Thieme-Verlag (Stuttgart) 1963, pages 248-2~9, and G.M. Kosolapoff and L. Maier, Organic Phosphorus Compounds, vol. 6, Wiley-Interscience (New York) 1973).
The processes used here-tofore~ especially those in which PCl3 and R-PCl2 are used as starting materials for maklng the above phosphorus-con-taining esre-rs, are carried out at low temperatures and normal:Ly in the presence of a base for capturing resulting hydrogen chloride. The bases used therein cGmprise ammonia or o;rganic nitrogen bases, such as amines or pyridine. It is also customary for inert solve~ts to be used in the above prior processes.
During preparation9 it is necessary for base-hydrochloride .
to be filtered off, for the inert solvent to be removed, and for the phosphorus-containing ester to be then recovered normally by distillatlon. In other words the processes used heretofore for making phosphorus-containing esters are expensive and rendered complicate by the fact that they are carried out at low -temperatures of from ~30C up to ~20C, use solvents and bases for sequestering hydrogen chloride, and by the need to filter off base hydrochloride from the reaction mixture.
The present inven-tion now provides a process for 5~5~'~

making phosphorus-con-taining esters of the general ~ormula .
o X--P--Z

.in which X stands for an alkyl group having from 1 to 3 carbon atomsl an aryl group or an alkoxy group having from 3 to 6 carbon atoms, Y stands ~or an alkoxy group having from 3 to 6 ; carbon a-toms, and Z stands for a hydrogen atom, an alkyl group ha~ing from 1 to ~ carbon atoms or an aryl : group by reacting phosphohalogen compouncls of the general - formula .. B
. I
: A-P-C
t ;: 20 D
in which A and B each stand independently of one another for a chlorine or bromine atom, an alkyl group having ~rom 1 to 3 carbon atoms or ~- ~ an aryl group, C stands for a chlorine or bromine atom, and D ~tands for a free pair of electrons or ;: an oxyg~n atom with aliphatic alcohols having from ~ to 6 carbon atoms, ; 30 which comprises: mixing and thereby reacting in an .
', ~ 4 ~

.

unheated reaction zone in liquid phase the phosphohalogen compo-und with -the alipha-tic alcohol and delivering the resulting re~c-tion rnix-ture to the head of a s-team-heated packed column; feeding -the column's base portion with inert gas travelling upwardly therein coun-tercurren-tly wi-th respec-t -to -the reacti.on mixture; dis-tilling of~
overhead hydrogen halide, alcohol in excess and, alkyl halide, i~ any, toge-ther wi-th -the inert gas; par-tially - condensing and removing -the dis-tilled ma-tter; and removing resulting phosphorus-containing ester flowing downwardly in the column from the column head to the column base, from the column base portion, i~ desired in admixture with alcohol in excess.
Further preferred features of the present process provide:
a) ~or a phosphohalogen compound being solid at room temperature -to be heated to a -temperature a few degrees above i-ts melting point and to be used in - the form of the resulting melt;
b) for the alcohol to be used in proportions 1.2 up to 6 times the s-toichiometric quantity~ per mol o ~: phosphohalogen compound;
c) for the reaction zone to be supplied with 1 up to 10 liter of nitrogen per liter of reaction mixture per hour; and d) for 50 up to 250 liter of nitrogen per liter of reaction mixture per hour to be introduced as the inert gas into the base portion of -the packed column.
The phosphohalogen compounds which are useful in ., .

lOSO~ iZ
-th~ present process comprlse, fox eY~ample: phosphorus trichloride, me-thyldichlorophosphine, ethyldichlorophosphine, propyldichlorophosphine, phenyldichlorophosphine, me-thane phosphonic acid di.chloride, e-thanephosphonic acid dichloride, propanephosphonic acid dichloride, phenyl-~ phosphonic acid dichloride, dimethylphosphinic acid h ~chloride, di.ethylphosphinic acid chloride, dipropyl-phosphinic acid ch]oride, me-thylethylphosphinic acid chloride, methylpropylphosphinic acid chloride, ethyl-propylphosphinic acid chloride, diphenylphosphinic acid chloride, and the corresponding bromidesO
..
The alcohols which may be used in -the process of the present invention comprise, for example n-propanol, iso-; propanol, n-butanol or lso-butanol, this latter al~ohol being preferred, and should convenien-tly con-tain less than 0.5 weight %, preferably less than 0.1 weight % of water.
In carrylng ou-t the procesLs.of -the presen~t lnvention, it is good practice for the phosphohalogen compound::, which ls at room temperature (18-30C) or heated to its .. 20 mel-ting poin~ a ~ew degrees above room temperature, to.
.be introduced together with -the alcohol9 which is also at room tempera-ture, into -the mixing/reaction-zone.
Reac-tion heat is set free whereby the mixture becomes ~ spon-taneously hea-ted wi-thou-t boiling. The reaction zone may be cooled from the outside by means of water, but this is unnecessary in most cases. I-t is even generally arlvantageous to omit the abstraction of heat and to immediately deliver the reaction mixture to the head of the packed separating column, in which nitrogen flowing countercurrently -to the reac-tion mixture,: causes :; _ 6- :

,, ~ ~5~ ~6~
resulting hydrogen halide to be distilled off to~e-ther with a por-tion o~ alcohol in excess and together with alkyl halide~ iE any, and to deliver the distilled ma-tter -to a condensa-tiorL and absorp-tion sys-tem placed downs-tream of the separating column. Phosphorus-containing ester and a portion of alcohol in excess -travel downwardly in the separating column and are continuously taken from -the column's base por-tion.
The reaction produc-ts so obtained are Eurther processed by conventional me-thods. It is possible, for example, Eor the phosphorus-con-taining ester -to be freed from alipha-tic alcohol in excess by distillative -trea-tment9 iE desired after neutraliza~tion of the solution. The distilled mat-ter comprised of hydrogen halide, aliphatic alcohol and alkyl hallde, iE any, is equally separated into its componen-ts by conventional methods which provide .
I -- Eor the recovery of alcohol.
The process of the present invention has unexpectedly been found to make i-t substantially impossible for resulting hydrogen halide to decompose the phosph~rus~
' contalning ester, inasmuch as the ni-trogen, which is caused to travel countercurrently.to the phosphorus-containing es-ter in the separating column, enables the hydrogen halide to be removed at an early stage from the column head. In other words, the hydrogen halide is in contact with the phosphorus-c~ntaining ester :Eor a considerably shortened period of time.
The process oE the pres.ent invention compares favorably with the prior art methods in respec-t of the fol~owing points:

, ; - 7 -,. . ~ : , . ; . . ', I-t enables the ph~sphorus-con-taining ester to be very rapidly separated in speci~ic manner :from hydrogen halide, which is ob-tained simul-taneously wi-th the ester.
As a result, -the hydrogen halide is less likely -to ca-talyze the decomposi-tion of -the phosphorus~con-taining ester which is accordingly ob-tained in improved yields.
In -the prior ar-t methods, it is necessary -to use bases 7 such as ammonia or organic amines, so as to bind -the overall quan-tity of hydrogen halide in the form of ammonium or amine hydrohalide salts which precipi-ta-te and have to be fil-tered of~ wi-th heavy loss of ma-terial. In view of the fac-t that the base-hydrohalides partially remain in the dissolved state, it is possible ~or -them to catalyze the decomposition of the phosphorus-containing - es-ters, whereby the yield becomes impaired. These ad~lerse effects are not encountered in the presen-t process yielding the phosphorus-containing es-ters in more concentra-ted form than any process described hereto~ore.
In the processes described heretofore, wherein phosphohalogen compounds are reac-ted ba-tchwise with aliphatic alcohols, it is necessary to initially remove ~he hea-t set ~re`e by the exothermal reaction through the walls o~ the reactor. Only then is it possible to neutralize, e~ually in a s-trongly exothermal operation, thé hydrogen halide which remains dissolved. Once again, it is necessary to abstract the hea-t through -the walls `
of the reactor, this time in a medium which becomes increasingly more concentrated by precipita-ting solid ; 30 base-hydrohalide. In the above known processes, e.g. in ' ~ 5~
-those wllich use ammonia as the base and a chlorine-containing phosphorus compound, it is also necessary ~or precipi-tated microcrystalline ammonium ch]oride to be stirred ~or several hours in -the reac-tion medium -to cause recrystalliza-tion and transforma-tion of the salt into fil-terable ma-terial.
; O:E subordinate importance in -the present process, which provides ~or an uninterrupted flow o~ starting material and final produc-t through the reaction zone, is the capacity or size o~ the apparatus used for commercial operation. This is in clear contras-t wi-th the batchwise preparation described heretofore, where the space/-time yield ob-tainable is critically de-termined and in fac-t ' limited by the cooling sur~ace of the reactor, and where very expensive rneans are required to be used for filtering -the base-hydrohalide.
~; Phosphorus-containing esters having P-H bonds are interesting starting ma-terials for making ~lame-retardant agents ~or use in polyesters, polyurethanes and poly-acrylonitrile, ~or example. They are very pure and accordingly very well adapted for use as reac-tants in reactions which are catalyzed by radical-yielding material.
EXAMPLE 1: (Methanephosphonous acid monoisobu-tyl-ester; c~. equation (2)).
~ n apparatus such as tha-t shown in the accompanying drawing was used. 288 g (3.88 mol) of- isobutanol coming ~rom a reservoir ~1) and 215 g (1.84 mol) o~ methyl-dichlorophosphine coming :~rom a reservoir (2) were introduced within 3.5 h at room temperature into the .. .. . .. .. . .. .. . .. .. ... . .. _ .. .. . .. . . . .. .... . .
apparatus (3), which was simultaneouyly charged wi-th - g _ . .

, . , ' , ; ', ' " '. ' ' :

~ o5056Z
5 l/h of nitrogen. F~lowing this, ..... . . .. .. . . . ........ ... . . .. .
-the reac-tion mix-ture was delivered -to -the head of a separa-ting column (L~) heated with s-team at 100C.
Ni-trogen was in-troduced into the column base a-t a ra-te of 100 l/h, which caused the resul-ting hydrogen chloride -to dis-til over -toge-ther wi-th a por-tion of isobutanol in excess and together wi-th resulting isobutyl chloride, and go i.nto a condenser (6). A-t the same tirne, base product was taken from the column through a line (5) and collected~ It was subjec-ted to gas-chroma-tography and found -to contain 228 g of methanephosphonous acid rnonoisobutylester (1.67 mol, corresponding -to 91 % of the theoretical). Altogether 1.80 mol of hydrogen chloride (98 % of -the theoretical) was identified by titra-tion in the collected distilla-te removed through a line (7), and in a HCl-absorption system (no-t shown in the drawing) downs-tream of line (8). The nltrogen escaped through the HCl-absorption system.
EXAMPL~.2: (Methanephosphonous acid monoisobutyl-: 20 es-ter; cf. equation (2)).
640 g (8.63 mol)~of isobutanol was reacted with 229 g (1.96 mol) of methyldichlorophosphine in the manner described in Example 1.
The base product was subjected to gas-chromatography and ~ound to contain 265 g of me-thanephosphonous acid monoisobutyIester.(1.95 mO17 corresponding -to 99 % of the theoretical). . .
Altoge-ther 1~96 mol of hydrogen chloride (100 % of the theoretical) was identified in -the distillate and in the HCl-absorption system.
.

EX~PL~ 3: (Me-thanephosphonous acid monoisobu-tyl es-ter; cf. equa-tion (2)).
464 g (6.26 mol) of isobu-tanol was reacted with 118 g (1.01 mol) of methyldichlorophosphine in -the manner ; described in Example 1-; The base product was subjected -to gas-chromatography and found to contain 135 g of me-thanephosphonous acid monoisobu-tyles-ter (0.99 mol 9 corresponding -to 98 % of ; -the theoretical). The base product had an acid number of

2.0 mg KOH/g.
Altogether 1.00 mol of hydrogen chloride (99 % of the -theore-tical) was identified in the distillate and in the HCl-absorption sys-tem.
EXAMPLE 4: (Comparative Example) A solution of 58.5 g ~0~5 mol) of methyldichloro-phosphine in 300 cc of anhydrous ether was admixed dropwise, with agitationj while cooling and w~lile introducing nitrogen thereinto, with 88.8 g (1.2 mol) of iso-butanol and 50.5 g (0~5 mol) of triethanolamine in ~20 100 cc of anhydrous e-ther. Following this, the whole was - heated for 30 minutes at 35C under reflux~ cooled down `!: . .
to 5C and ~iltered. The resulting filtrate was concentrated and vacuum-dlstilled under nitrogen~ Iso-` bu-tanol and iso-butyl chloride in excess were removed wi-th ~ ..... . .
the ~irst runnings. The main runnings contained 59.8 g (0.44 mol) of methanephosphonous aci~d monoisobutylester (88 % o~ the -theoretical).
EXAMPLE 5: (ComparatiYe Example) 2220 g (30 mol) of isobutanol was placed in a reaction ~lask and 585 g (5 mol) of me-thyldichlorophosphine .
_ 11 - ~ ' , .

s~
~as added within ? hours wi-th agita-tion, while in-troducing nitro~en and while cooling down -to less than Following this, -the whole was neutralized over a period of 3 hours by means of gaseous ammonia while cooling down to less -than 30C and wi-th agi-tation, The whole was stirred -Eor abou-t 8 h at room temperature -to cause recrystalliza-tion, and suc-tion-fil-tered. The resulting ~il-ter cake was washed twice, each time with 200 g of isobu-tanol-. The filtrate (3220 g) was subjected to gas~chromatography and found to contain 19.2 %
; ( 615 g = 4. 52 mol) of methanephosphonous acid ~; monoisobutylester (90.5 % of the theore-tical).
EXAMPLE 6: (Diisobutylphosphite ; c~. equation (1)).
400 g (5.40 mol) of isobutanol was reac-ted wi-th 191 g (1.39 mol) of phosphorus~ chloride in the manner described in Example 1.
~ The base produc-t was subjected to gas-chromatography ; ~ and ~nd to con-tain 255 g of diisobutylphosphite (1.31 mol, corresponding to 94 % of the theoretical).
The base product had an acid number o~ 2.4 mg KOH/g.
Altogether Z.78 mol (100 % o~ the theoretical) of hydrogen chloride was iden-tified in the dis-tilla-te and ~ in the HCl-absorption system.
! ~ ~e~a~e~h~s~o~
1~ EXAMPLE 7: ~Mcth~ncpho~ph~r~u~ acid diisobutylester;
.
cf. equation (3)).
424 g (5.72 mol) of isobutanol was reacted in the manner described in Example 1 with 168 g (1.26 mol) o~
7~ e-~ an ~ D h o5 ~h ~ c me~h~h~hff~ acid dichloride coming from reservoir (2) which was heated to 45C. The resul-ting base produc-t .

~,... . . ... . . .

was subjected to gas-chromatography and found to contain 250 g of methanephosphonic acid diisobutylester (1.20 mol, corresponding to 95 % of the theoretical). The base product had an acid number of 7.8 mg KOH/g.
Altogether 2.44 mol (97 % of the theoretical) of hydrogen chloride was identified in the distillate and in the HCl-absorption system.
EXAMPLE 8: (Methanephosphonic acid diisobutylester;

cf. equation (3)).
640 g (8.63 mol) of isobutanol was reacted with 189 g (1.42 mol) of methanephosphonic acid dichloride in the manner described in Example 1.
The resulting base product was subjected to gas-.... . .
chromatography and found to contain 291 g of methane-phosphonic acid diisobutylester (1.40 mol, corresponding to 99 % of the theoretical~. The base product had an acid number of 5.5 mg KOH/g.
Altogether 2.86 mol Cl% Of the theoretical) of hydrogen chloride was identified by titration in the distillate and in the HCl-absorption system.
EXAMPLE 9: (Dimethylphosphinic acid isobutylester;
cf. equation ~4)).
600 g ~8.09 mol) of isobutanol was reacted in the manner described in Example 1 with 159 g ~1.41 mol) of liquid dimethylphosphinic acid chloride coming from reservoir ~2) which was heated to 80C.
The resulting base product was subjected to gas-chromatography and found to contain 192 g of dimethyl-phosphinic acid isobutylester ~1.28 mol, corresponding to 91 % of the theoretical).

, . : , . .
,: - ~ : . : , . . , ,: ,, , i6~
Altoge-ther 1.08 mol (76 % of the theoretical) of hydrogen chloride was identified in the distillate and in the HCl-absorption systemO The base product contained 0.12 mol of hydrogen chlorideO (determination o~
chloride and acid number).

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
THE CLAIMS:

1) A process for making phosphorus-containing esters of the general formula in which X stands for an alkyl group having from 1 to 3 carbon atoms, an aryl group or an alkoxy group having from 3 to 6 carbon atoms, Y stands for an alkoxy group having from 3 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 phosphohalogen compounds of the general formula in which A and B each stand independently of 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 3 to 6 carbon atoms, which comprises: mixing and thereby reacting in an unheated reaction zone in liquid phase the phospho-halogen compound with the aliphatic alcohol and delivering the resulting reaction mixture to the head of a steam-heated packed column; feeding the column's base portion with inert gas travelling upwardly therein countercurrently with respect to the reaction mixture;
distilling off overhead hydrogen halide, alcohol in excess and, alkyl halide, if any, together with the inert gas; partially condensing and removing the distilled matter; and removing resulting phosphorus-containing ester flowing downwardly in the column from the column head to the column base, from the column base portion.

2) A process as claimed in claim 1, wherein the phosphorus-containing ester flowing downwardly in the column is removed from the column base portion in admixture with alcohol in excess.

3) A process as claimed in claim 1, wherein a phospho-halogen compound being solid at room temperature is heated to a temperature a few degrees above its melting point and used in the form of the resulting melt.

4) A process as claimed in claim 17 wherein the alcohol is used in proportions 1.2 up to 6 times the stoichiometric quantity, per mol of phosphohalogen compound.

5) A process as claimed in claim 1, wherein the reaction zone is supplied with 1 up to 10 liter of nitrogen per liter of reaction mixture per hour.

6) A process as claimed in claim 1, wherein 50 up to 250 liter of nitrogen per liter of reaction mixture per hour is introduced as the inert gas into the base portion of the packed column.