Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus esters
Patent
1997-07-21
2000-06-13
Ambrose, Michael G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus esters
558119, C07F 912, C07F 911, C07F 909
Patent
active
060751584
DESCRIPTION:
BRIEF SUMMARY
This application is filed under 35 U.S.C. .sctn. 371 and is the National Stage of International Application No. PCT/GB95/01883, filed Aug. 9, 1995.
This invention relates to a novel process for the production of esters of oxyacids of pentavalent phosphorus by the transesterification of an ester of such an oxyacid of phosphorus with an alcohol or phenol. In a first preferred embodiment the invention provides a process for the production of triakyl, dialkylphenyl and alkyldiphenyl phosphates by the transesterification of triphenyl phosphate with an aliphatic alcohol. In a second preferred embodiment the invention provides a process for the production of tris (alkaryl) phosphates by the transesterification of triphenyl phosphate with an alkylated phenol.
BACKGROUND OF THE INVENTION
A large number of esters oxyacids of pentavalent phosphorus are produced as articles of commerce e.g. phosphates, thiophosphates and phosphonates. The majority of them are produced by the reaction of an alcohol or phenol with phosphorus oxychloride or with a chloridate. Such reactions are inherently disadvantageous in so far as they involve the handling of chlorine or a derivative thereof.
The present invention finds particular application to processes for the production of phosphate esters. Triaryl phosphates are produced in large quantities by the reaction of phenol or alkyl substituted phenols or a mixture of such phenols with phosphorus oxychloride. Monoalkyl diaryl phosphates are produced by the reaction of phosphorus oxychloride with one molar proportion of an alcohol and the subsequent reaction of the dichloridate produced with a phenate anion.
There have been proposals to produce mixed alkylaryl phosphate esters by the transesterification of a triaryl phosphate such as triphenyl phosphate with an aliphatic alcohol. Finley, U.S. Pat. No. 4,443,384, discloses carrying out such a transesterification by initially adding aqueous sodium hydroxide to the alcohol to form an alkoxide and subsequently reacting that alkoxide with the triaryl phosphate. Finley, U.S. Pat. No. 4,482,506, discloses carrying out such a transesterification in the presence of a phenoxide catalyst. The phenoxide is stated to function by virtue of interacting with the alcohol to generate an alkoxide and the reaction is effected by initially reacting the phenoxide with the alcohol and subsequently adding the triaryl phosphate. None of these proposals has been entirely successful in producing a high yield of alkyl aryl phosphate (i.e., a product containing only small amounts of unreacted triaryl phosphate) and all suffer from a tendency towards by-product formation and concomittant catalyst deactivation. The manufacture of phosphate esters has continued to be practised on a large scale using phosphorus oxychloride or a chloridate as a raw material despite the attendant disadvantages thereof.
SUMMARY OF THE INVENTION
We have now discovered that the transesterification of an ester of an oxyacid of pentavalent phosphorus with an alcohol or phenol can be carried out efficiently in the presence of a catalytic quantity of a base B having a base strength (expressed as the pK.sub.a of the conjugate acid BH.sup.+) of less than 11.
DETAILED DESCRIPTION OF THE INVENTION
In this specification the base strength of a base B is defined by reference to the equilibrium acid BH.sup.+ ##EQU1## and these concentrations are measured in aqueous solution at 25.degree..
Bases having a base strength of greater than 11 (such as alkoxide which has a base strength of approximately 14) have been found to be less effective in so far as they tend to promote competing reactions. This not only reduces the yield of the desired product but also leads to the poisoning of the basic catalyst by acidic products of these competing reactions. The milder bases having a base strength of less than 11 have been discovered to be more selective in favouring the transesterification reaction and more active apparently due at least in part to the reduced quantities of acidic by-products which are gener
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JACS 85, No. 22, Nov. 20, 1963 3533-3539 PCT.
Ogilvie, K.K. and S.L. Beaucage. "Fluoride Ion-promoted Transesterification in Phosphate Triesters." J. Chem. Soc. Chem. Commun., 443, Jul. 1976.
Ambrose Michael G.
Great Lakes Chemical Corporation
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