WO2005121060A1 - Process for the synthesis of polyfluorocarboxylic acids - Google Patents

Process for the synthesis of polyfluorocarboxylic acids Download PDF

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Publication number
WO2005121060A1
WO2005121060A1 PCT/EP2005/007060 EP2005007060W WO2005121060A1 WO 2005121060 A1 WO2005121060 A1 WO 2005121060A1 EP 2005007060 W EP2005007060 W EP 2005007060W WO 2005121060 A1 WO2005121060 A1 WO 2005121060A1
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acids
sulphinates
process according
synthesis
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PCT/EP2005/007060
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French (fr)
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Patrick Kappler
Marie-José Lina
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Arkema
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen

Definitions

  • Patent US 2 519 983 discloses the hydrolysis of the corresponding acid fluorides CF 3 (CF 2 CF 2 ) m COF, themselves obtained by electrochemical fluorination of the carboxylic acids CH 3 (CH 2 CH 2 ) m COOH.
  • Patent US 3 255 228 discloses the reaction of oleum with CF 3 (CF 2 CF2)ml and hydrolysis of the sulphates.
  • Patent DE 1 916 669 discloses the oxidation with dichromate of the ethylenated derivatives CF 3 (CF 2 CF 2 ) m CH 2 CH 2 -I.
  • Patent US 4 751 027 discloses the oxidation of the olefins
  • Patent EP 0 526 976 discloses the oxidation of the alcohols CF 3 (CF 2 CF 2 ) m (CH 2 ) 2 ⁇ H with the Jones reagent. Partially fluohnated carboxylic acids are also described by the prior art.
  • Patent FR 2 220 504 discloses the preparation of the acids R f (CH 2 CF 2 ) m-1 CH 2 -COOH by reaction of nitric acid with R f (CH 2 CF 2 )ml
  • Patent FR 2 220 505 discloses the synthesis of the acids R f [CH 2 C(R1 )F] m CH 2 CH 2 -COOH by hydrolysis of the corresponding nitriles
  • Patent Application US 2002-0147357 discloses the reaction of perfluoroalkyl iodide with oxygen under photochemical activation by UV radiation. All these processes are either highly polluting, or difficult to control (such as the oxidations), or involve very specific equipment (as in the case of the ozonolysis and the photochemical reactions).
  • Another synthetic method consists in starting from the sulphinates
  • R f (CX 2 CF 2 ) m SO 2 Na The conversion of the sulphinates can be carried out by analogy with the method described by Chinese researchers of the Shanghai Institute of Organic Chemistry, who, starting from perhalofluoroalkylated sulphinates and from an oxidizing or redox system, (NH 4 ) 2 S 2 0 8 , Ce(S0 4 ) 2 or 2+ H 2 0 2 /Fe , obtained perhalofluorocarboxylic acids (Journal of Fluorine Chemistry, 49, 1990, pp.
  • the sulphinates of general formula Rf(CX 2 CF 2 ) m S0 2 Na [2] can be prepared by analogy with known techniques described, for example, by Roesky [Angew. Chem. Int Ed. English, Vol. 18. pages 810-811 (1971 )] or by Chang- Ming Hu [J. Org. Chem., Vol 6. No. 8, 1991 , page 2803], by reaction of sodium hydrosulphite (dithionite) with the iodinated precursor in a water/acetonitrile or water/ethanol medium in the presence of an alkaline earth metal neutralizing agent, preferably sodium hydrogenocarbonate, or else according to the process disclosed in Patent FR 2 823 204.
  • an alkaline earth metal neutralizing agent preferably sodium hydrogenocarbonate
  • the radical initiators used in the context of the present invention for conversion of the sulphinates [2] to carboxylic acids [1] can be chosen from the known classes of peroxides and diazo compounds.
  • the radical generators selected by the Applicant Company are preferably azo compounds.
  • the amount of initiator can vary, for example, from 0.01 to 0.2 in molar ratio with respect to the sulphinate. It will preferably be added in solution and slowly, so as to generate the radicals little by little in order to avoid radical secondary reactions.
  • the reaction will preferably be carried out in a homogeneous medium in an organic solvent or in water at a concentration which can vary, according to the solubility of the precursor sulphinates, from a few per cent to 70-80% by weight, preferably between 10 and 30%.
  • the reaction temperature will depend on the radical initiator used.
  • the reaction medium can be one or more polar organic solvents in which the sulphinates are soluble, such as, for example, alcohols, esters and ketones.
  • the choice will preferably be made of the ester which was used beforehand to extract the intermediate sulphinate from the aqueous solution, such as ethyl or isopropyl acetate.
  • a radical initiator from the family of the commonest azo compounds, such as 2,2'-azobisisobutyronitrile (AZDN ® from ATOFINA) or 2,2'-azobis(2-methylbutanenitrile) (Vazo ® 67 from DuPont).
  • a water-soluble azo initiator will be chosen, such as the following commercial products: 4,4'-azobis(4-cyanopentanoic acid) (Azocarboxy ® from ATOFINA), 2,2'-azobis(2-amidinopropane) hydrochloride (V50 from Wako) or 2,2'-azobis[2- (2-imidazolin-2-yl)propane] hydrochloride (Vazo ® 44WSP from DuPont).
  • the conversion of the sulphinates [2] to carboxylic acids [1] can advantageously be carried out in the reaction medium for the synthesis of the sulphinate precursors without isolation of the latter and without removing the by- products and inorganic salts before addition of the radical initiator.
  • the carboxylic acids formed according to the invention can be isolated either by separation by settling or filtration or by extraction with an organic solvent and then evaporation of the latter.
  • the invention is of particular use for the following compounds: C 2 F 5 (CH 2 CF 2 ) 3 CH 2 COOH; C 4 F 9 (CH 2 CF 2 ) 2 CH 2 COOH; CsFnCOOH; C 7 F 15 COOH and C 9 F 19 COOH; (CF 3 ) 2 CF(CF 2 ) 5 COOH
  • Example 1 Synthesis of sodium polyfluorohexylsulphinate: C 2 F 5 -(CH 2 -CF 2 ) 4 -S0 2 Na [3] The following are introduced with stirring into a 500 ml three-necked round- bottomed flask equipped with a mechanical stirrer, an upright reflux condenser, a dropping funnel and a temperature probe: 180 g of demineralized water, 12.6 g of NaHC0 3 (0.15 mol) and 26.1 g of sodium hydrosulphite Na 2 S 2 0 4 (0.15 mol).
  • Example 2 Conversion of the sulphinate [3] to the carboxylic acid 4.62 g of sulphinate [3] (0.01 mol) and 30 g of demineralized water are charged to a 250 ml three-necked round-bottomed flask equipped with a mechanical stirrer, an upright reflux condenser and a temperature probe. The mixture is heated to 55°C and then a solution of 0.34 g of 2,2'-azobis- (2-methylpropionamidine) dihydrochloride (Aldrich) in 20 g of water is added thereto dropwise over 1 h 30. After stirring at 55°C for 5 hours, the gel formed is separated by settling and then extracted with diisopropyl ether.
  • Aldrich 2,2'-azobis- (2-methylpropionamidine) dihydrochloride
  • Example 4 Conversion of the sulphinate [5] to the carboxylic acid 4.06 g of sulphinate [5] (0.01 mol) and 30 g of demineralized water are charged to a 250 ml three-necked round-bottomed flask equipped with a mechanical stirrer, an upright reflux condenser and a temperature probe. The mixture is heated to 55°C and then a solution of 0.34 g of 2,2'-azobis- (2-methylpropionamidine) hydrochloride (Aldrich) in 20 g of water is added thereto dropwise over 1 h 30.
  • Aldrich 2,2'-azobis- (2-methylpropionamidine) hydrochloride
  • the gel formed is extracted with 50 g of diisopropyl ether at 30°C in the presence of 10 g of NaCI.
  • the organic phase is washed with a saturated NaCI solution to pH 3.5 and then dried over Na 2 S0 .
  • a light yellow liquid is collected with a yield of 75%. It exhibits, in the IR spectrum, a band characteristic of the -COOH groups in the position with respect to a -CF 2 group at 1770 cm "1
  • the NMR analysis shows that it is essentially carboxylic acid C 5 FnCOOH (C 2 F 5 -(C 2 F 4 )-CF 2 COOH), partially in the carboxylate form.
  • Example 5 Synthesis of sodium perfluorooctylsulphinate: C 2 F 5 -(C 2 F 4 ) 3 -S0 2 Na [6]
  • the synthesis is carried out as in Example 3, C 6 F 13 I being replaced mole for mole by C ⁇ F ⁇ 7 l.
  • the ethanol is removed by distillation.
  • the two-phase mixture obtained is extracted with 280 g of ethyl acetate.
  • the organic phase is washed with 200 g of a saturated NaCI solution and dried over Na 2 S0 4 .
  • the solvent is subsequently removed by distillation on a rotary evaporator under reduced pressure.
  • the white solid recovered is purified by washing with 60 g of isopropanol to remove the traces of iodinated derivatives. The analyses show that it is indeed
  • Example 6 Conversion of the sulphinate [6] to the carboxylic acid The conversion is carried out as in Example 4, the sulphinate
  • Example 7 The synthesis is carried out as in Example 1 up to complete conversion of the iodinated polymer.
  • the temperature of the reaction mixture obtained is lowered to 55°C and then a solution of 3.4 g of 2,2'-azobis(2-methylpropion- amidine) dihydrochloride (Aldrich) in 50 g of water is added thereto little by little over 1 h 30.
  • the ethanol is removed by distillation under reduced pressure and the carboxylic acid formed is extracted with diisopropyl ether.
  • the organic phase is washed with water to pH 3.5 and then dried over Na 2 S0 . After evaporating the solvent, the acid is collected with a yield of 90%.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention relates to a process for the preparation of the acids of formula: Rf(CX2CF2)m-1CX2COOH by reaction of the sulphinates of formula: Rf(CX2CF2)m SO2Na with a radical initiator, in which formulae m is an integer from 2 to 6, Rf is a linear or branched perfluoroalkyl group comprising from 1 to 6 carbon atoms, X= F or H. According to one advantageous form, Rf is a linear or branched perfluoroalkyl group comprising from 2 to 4 carbon atoms. According to another advantageous form, m is an integer from 3 to 5.

Description

Field of the invention PROCESS FOR THE SYNTHESIS OF POLYFLUOROCARBOXYLIC ACIDS Polyfluorocarboxylic acids possess noteworthy properties. The very strong C-F bonds and the characteristics of the fluorine atoms (high electronegativity, small size and low polarizability) confer excellent emulsifying properties, good thermal stability and good chemical stability. Polyfluorocarboxylic acids are consequently used for the polymerization of fluoromonomers. The invention relates to a novel process for the synthesis of the acids of formula Rf(CX2CF2)m.ιCX2COOH in which: m is an integer from 2 to 6,
Rf is a linear or branched perfluoroalkyl group comprising from 1 to 6 carbon atoms, X = F or H. The prior art and the technical problem The prior art has already described processes for the preparation of perfluorocarboxylic acids with the structure CF3(CF2CF2)mCθ2M. Patent US 2 519 983 discloses the hydrolysis of the corresponding acid fluorides CF3(CF2CF2)mCOF, themselves obtained by electrochemical fluorination of the carboxylic acids CH3(CH2 CH2 )mCOOH. Patent US 3 255 228 discloses the reaction of oleum with CF3(CF2CF2)ml and hydrolysis of the sulphates. This process is highly polluting. Furthermore, the recovery of the iodine is particularly difficult therein. Patent DE 1 916 669 discloses the oxidation with dichromate of the ethylenated derivatives CF3(CF2CF2)m CH2CH2-I. Patent US 3 525 758 discloses the oxidation with K2Cr207 of the olefins (CF3)2CF(C2F4)n-CH=CH2 . Patent US 4 138417 discloses the ozonolysis of the olefins CF3(CF2CF2)mCH=CH2 . Patent US 4 751 027 discloses the oxidation of the olefins
CF3(CF2CF2)mCH=CH2 by potassium permanganate in the presence of a phase transfer catalyst. Patent US 5 945 562 discloses the oxidation of the olefins CF3(CF2CF2)mCH=CH2 by bleach in the presence of Ru02 catalyst. Patent EP 0 526 976 discloses the oxidation of the alcohols CF3(CF2CF2)m(CH2)2θH with the Jones reagent. Partially fluohnated carboxylic acids are also described by the prior art.
Mention may be made of: Patent FR 2 220 504, which discloses the preparation of the acids Rf(CH2CF2)m-1CH2-COOH by reaction of nitric acid with Rf(CH2CF2)ml, Patent FR 2 220 505, which discloses the synthesis of the acids Rf[CH2C(R1 )F]mCH2CH2-COOH by hydrolysis of the corresponding nitriles, Patent US 5 763 552, which, among the products with the structure R CH2)mRf-C02M, discloses, for example, the preparation of CeFι3-CH2-CF2- COOH from C6Fι3-(CH2-CF2)n-CH=CF2. Patent Application US 2002-0147357 discloses the reaction of perfluoroalkyl iodide with oxygen under photochemical activation by UV radiation. All these processes are either highly polluting, or difficult to control (such as the oxidations), or involve very specific equipment (as in the case of the ozonolysis and the photochemical reactions). Another synthetic method consists in starting from the sulphinates
Rf(CX2CF2)mSO2Na. The conversion of the sulphinates can be carried out by analogy with the method described by Chinese researchers of the Shanghai Institute of Organic Chemistry, who, starting from perhalofluoroalkylated sulphinates and from an oxidizing or redox system, (NH4)2S208, Ce(S04)2 or 2+ H202/Fe , obtained perhalofluorocarboxylic acids (Journal of Fluorine Chemistry, 49, 1990, pp. 433-437) and, by photooxidation under UV irradiation in methanol with a high-pressure mercury lamp at ambient temperature and in the presence of oxygen, identified the corresponding methyl esters {Tetrahedron Letters, 30, No. 48, pp. 6717-6720). It has been observed, unexpectedly, that the sulphinates of general formula Rf(CH2CF2)mS02Na decompose very slowly in water in the presence of atmospheric oxygen to give acids Rf(CH2CF2)m-ιCH2COOH. However, this conversion is very slow, whatever the operating conditions. Consequently, it cannot be of any industrial interest. It has now been found that it is possible to obtain polyfluoro- or perfluorocarboxylic acids in a much simpler way by conversion of sulphinates under mild conditions using organic radical initiators.
Brief description of the invention The invention relates to a process for the preparation of the acids of formula Rf(CX2CF2)m-1CX2COOH [1] by reaction of the sulphinates of formula: Rf(CX2CF2)m S02Na [2] with a radical initiator, in which formulae m is an integer from 2 to 6, Rf is a linear or branched perfluoroalkyl group comprising from 1 to 6 carbon atoms, X = F or H. According to one advantageous form, Rf is a linear or branched perfluoroalkyl group comprising from 2 to 4 carbon atoms or a mixture of homologues. According to another advantageous form, m is an integer from 3 to 5.
Detailed description of the invention The sulphinates of general formula Rf(CX2CF2)mS02Na [2] can be prepared by analogy with known techniques described, for example, by Roesky [Angew. Chem. Int Ed. English, Vol. 18. pages 810-811 (1971 )] or by Chang- Ming Hu [J. Org. Chem., Vol 6. No. 8, 1991 , page 2803], by reaction of sodium hydrosulphite (dithionite) with the iodinated precursor in a water/acetonitrile or water/ethanol medium in the presence of an alkaline earth metal neutralizing agent, preferably sodium hydrogenocarbonate, or else according to the process disclosed in Patent FR 2 823 204. The iodinated precursors Rf(CX2CF2)m-l of the compounds according to the invention are obtained, in a well-known way, by telomerization of perfluoroalkyl iodide CnF2n+ιl with vinylidene fluoride (X = H) or with tetrafluoroethylene (X = F), for example in the liquid phase in the presence of an initiator of peroxide type or else in the gas phase by thermal telomerization. The radical initiators used in the context of the present invention for conversion of the sulphinates [2] to carboxylic acids [1] can be chosen from the known classes of peroxides and diazo compounds. However, peroxide compounds can result in side reactions and can in particular partially convert sulphinates to sulphonates. The radical generators selected by the Applicant Company are preferably azo compounds. The amount of initiator can vary, for example, from 0.01 to 0.2 in molar ratio with respect to the sulphinate. It will preferably be added in solution and slowly, so as to generate the radicals little by little in order to avoid radical secondary reactions. The reaction will preferably be carried out in a homogeneous medium in an organic solvent or in water at a concentration which can vary, according to the solubility of the precursor sulphinates, from a few per cent to 70-80% by weight, preferably between 10 and 30%. The reaction temperature will depend on the radical initiator used. By way of example, it is between 45 and 70°C. The reaction medium can be one or more polar organic solvents in which the sulphinates are soluble, such as, for example, alcohols, esters and ketones. In order to avoid secondary reactions, the choice will preferably be made of the ester which was used beforehand to extract the intermediate sulphinate from the aqueous solution, such as ethyl or isopropyl acetate. In this case, it will be possible to use a radical initiator from the family of the commonest azo compounds, such as 2,2'-azobisisobutyronitrile (AZDN® from ATOFINA) or 2,2'-azobis(2-methylbutanenitrile) (Vazo®67 from DuPont). It may be advantageous to carry out the reaction in an aqueous medium. As the majority of fluorinated sulphinates are soluble in water, a water-soluble azo initiator will be chosen, such as the following commercial products: 4,4'-azobis(4-cyanopentanoic acid) (Azocarboxy® from ATOFINA), 2,2'-azobis(2-amidinopropane) hydrochloride (V50 from Wako) or 2,2'-azobis[2- (2-imidazolin-2-yl)propane] hydrochloride (Vazo® 44WSP from DuPont). The conversion of the sulphinates [2] to carboxylic acids [1] can advantageously be carried out in the reaction medium for the synthesis of the sulphinate precursors without isolation of the latter and without removing the by- products and inorganic salts before addition of the radical initiator. The carboxylic acids formed according to the invention can be isolated either by separation by settling or filtration or by extraction with an organic solvent and then evaporation of the latter. The invention is of particular use for the following compounds: C2F5 (CH2CF2)3CH2COOH; C4F9 (CH2CF2)2CH2COOH; CsFnCOOH; C7F15COOH and C9F19COOH; (CF3)2CF(CF2)5COOH
Examples
Example 1 : Synthesis of sodium polyfluorohexylsulphinate: C2F5-(CH2-CF2)4-S02Na [3] The following are introduced with stirring into a 500 ml three-necked round- bottomed flask equipped with a mechanical stirrer, an upright reflux condenser, a dropping funnel and a temperature probe: 180 g of demineralized water, 12.6 g of NaHC03 (0.15 mol) and 26.1 g of sodium hydrosulphite Na2S204 (0.15 mol). A solution of 50.2 g of iodinated telomer C2F5-(CH2-CF2)4-I (0.1 mol) in 48 g of ethanol is added dropwise using the dropping funnel and then the reaction medium is heated at reflux for 4 hours. After removing the ethanol by distillation, the sulphinate obtained is extracted with ethyl acetate and the organic phase is washed with a saturated NaCI solution and dried over Na2S04. The solvent is subsequently removed by distillation on a rotary evaporator under reduced pressure at T < 60°C. The sulphinate C2F5-(CH2-CF2)4-S02Na [3] is obtained in the form of a white solid with a melting point of 86°C, with a yield of 95%
Example 2: Conversion of the sulphinate [3] to the carboxylic acid 4.62 g of sulphinate [3] (0.01 mol) and 30 g of demineralized water are charged to a 250 ml three-necked round-bottomed flask equipped with a mechanical stirrer, an upright reflux condenser and a temperature probe. The mixture is heated to 55°C and then a solution of 0.34 g of 2,2'-azobis- (2-methylpropionamidine) dihydrochloride (Aldrich) in 20 g of water is added thereto dropwise over 1 h 30. After stirring at 55°C for 5 hours, the gel formed is separated by settling and then extracted with diisopropyl ether. The organic phase is washed with water to pH 3.5 and then dried over Na2SO4. After evaporating the solvent under vacuum, a white solid with a melting point of 77°C is collected with a yield of 88%. It exhibits, in the IR spectrum, a band characteristic of the -COOH groups at 1706 cm"1). The NMR analysis shows that it is essentially carboxylic acid C2F5(CH2CF2)3-CH2C02H [4]
Example 3: Synthesis of sodium perfluorohexylsulphinate: C2F5-(CF2-CF2)2-S02Na [5]
52 g (0.3 mol) of sodium dithionite (Na2S204) are added to a jacketed reactor heated using a thermostatically-controlled bath which is equipped with a mechanical stirrer, an upright reflux condenser, a dropping funnel and a temperature probe and which contains 16 g (0.15 mol) of sodium carbonate (Na2C03) dissolved in 480 g of demineralized water. After dissolution, 89.2 g (0.2 mol) of C6F13I, in solution in 120 g of ethanol, are added thereto dropwise over 1/2 hour; the two-phase mixture obtained is brought to reflux (76°C) for 1h 30, giving a homogeneous colourless solution. After cooling, this solution is poured onto 180 g of ethyl acetate and 400 g of a saturated aqueous NaCI solution. After separating by settling, the organic phase is washed with a saturated NaCI solution and dried over Na2S04. The solvent is subsequently removed by distillation on a rotary evaporator under reduced pressure. The white solid recovered (79 g, Yd 97%) is C6F13S02Na [5] (MS/negative electrospray: peak at 383 = C6F13S02 "; NMR purity 97%).
Example 4: Conversion of the sulphinate [5] to the carboxylic acid 4.06 g of sulphinate [5] (0.01 mol) and 30 g of demineralized water are charged to a 250 ml three-necked round-bottomed flask equipped with a mechanical stirrer, an upright reflux condenser and a temperature probe. The mixture is heated to 55°C and then a solution of 0.34 g of 2,2'-azobis- (2-methylpropionamidine) hydrochloride (Aldrich) in 20 g of water is added thereto dropwise over 1 h 30. After stirring at 55°C for 5 hours, the gel formed is extracted with 50 g of diisopropyl ether at 30°C in the presence of 10 g of NaCI. The organic phase is washed with a saturated NaCI solution to pH 3.5 and then dried over Na2S0 . After evaporating the solvent under vacuum, a light yellow liquid is collected with a yield of 75%. It exhibits, in the IR spectrum, a band characteristic of the -COOH groups in the position with respect to a -CF2 group at 1770 cm"1 The NMR analysis shows that it is essentially carboxylic acid C5FnCOOH (C2F5-(C2F4)-CF2COOH), partially in the carboxylate form.
Example 5: Synthesis of sodium perfluorooctylsulphinate: C2F5-(C2F4)3-S02Na [6] The synthesis is carried out as in Example 3, C6F13I being replaced mole for mole by CβFι7l. After having heated the reaction mixture at reflux for 6 hours, the ethanol is removed by distillation. After cooling, the two-phase mixture obtained is extracted with 280 g of ethyl acetate. After separation by settling, the organic phase is washed with 200 g of a saturated NaCI solution and dried over Na2S04. The solvent is subsequently removed by distillation on a rotary evaporator under reduced pressure.
The white solid recovered is purified by washing with 60 g of isopropanol to remove the traces of iodinated derivatives. The analyses show that it is indeed
C8F17S02Na [6] (C2F5-(C2F4)3-SO2Na) (MS/negative electrospray: peak at
483 = C8F17S02 ").
Example 6 : Conversion of the sulphinate [6] to the carboxylic acid The conversion is carried out as in Example 4, the sulphinate
C6F 3S02Na [5] being replaced weight for weight by C8F17Sθ2Na [6] (0.079 mol). After stirring at 55°C for 5 hours, the gel formed is extracted with 70 g of isopropyl ether. The organic phase is washed with demineralized water to pH 3.5 and then dried over Na2S04. After evaporating the solvent under vacuum, a light yellow solid with a melting point of 54°C is collected. It exhibits, in the IR spectrum, a band characteristic of the fluorocarboxylates at 1701 cm"1. By NMR analysis, the C7F15COO" (or C2F5-(C2F4)2-CF2COO") represents 95.5 mol% of the CF3-CF2- chains.
Example 7 : The synthesis is carried out as in Example 1 up to complete conversion of the iodinated polymer. The temperature of the reaction mixture obtained is lowered to 55°C and then a solution of 3.4 g of 2,2'-azobis(2-methylpropion- amidine) dihydrochloride (Aldrich) in 50 g of water is added thereto little by little over 1 h 30. After stirring at 55°C for 7 hours, the ethanol is removed by distillation under reduced pressure and the carboxylic acid formed is extracted with diisopropyl ether. The organic phase is washed with water to pH 3.5 and then dried over Na2S0 . After evaporating the solvent, the acid is collected with a yield of 90%.

Claims

1 Process for the preparation of the acids of formula: Rf(CX2CF2)m-1CX2COOH by reaction of the sulphinates of formula:
Figure imgf000010_0001
with an organic radical initiator, in which formulae m is an integer from 2 to 6,
Rf is a linear or branched perfluoroalkyl group comprising from 1 to 6 carbon atoms, X = F or H.
2 Process according to Claim 1 , in which Rf is a linear or branched perfluoroalkyl group comprising from 2 to 4 carbon atoms. 3 Process according to either one of the preceding claims, in which m is an integer from 3 to 5.
4 Process according to any one of the preceding claims, in which X = H.
Process according to any one of Claims 1 to 3, in which X = F.
6 Process according to any one of the preceding claims, in which the radical initiator is an azo radical initiator.
7 Process according to Claim 6, in which the sulphinates are converted to carboxylic acids in an aqueous medium with water-soluble azo radical initiators. 8 Process according to any one of the preceding claims, in which the intermediate sulphinates are not isolated. 9 Process according to any one of the preceding claims, in which the acids are as follows:
C2F5(CH2CF2)3CH2COOH; C4F9(CH2CF2)2CH2COOH; C5FnCOOH; C7F15COOH and C9F19COOH; (CF3)2CF(CF2)5COOH.
PCT/EP2005/007060 2004-06-10 2005-06-01 Process for the synthesis of polyfluorocarboxylic acids WO2005121060A1 (en)

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU544027B2 (en) * 1977-04-20 1985-05-16 E.I. Du Pont De Nemours And Company Perhalocarboxylic acids by oxidation of perhalosulfinic acids

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU544027B2 (en) * 1977-04-20 1985-05-16 E.I. Du Pont De Nemours And Company Perhalocarboxylic acids by oxidation of perhalosulfinic acids

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
F.E. BEHR ET AL, J. FLUOR. CHEM., vol. 29, 1985, pages 122, XP002301662 *
H. CHANG-MING ET AL, J. FLUOR. CHEM., vol. 42, 1989, pages 145 - 148, XP002301661 *
H. CHANG-MING ET AL, J. FLUOR. CHEM., vol. 49, 1990, pages 433 - 437, XP002301660 *

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