Method for preparing a tetrafluoro-1,2-epoxypropane

Abstract

A method for preparing atetrafluoro-1,2-epoxypropane comprising reacting a 2-bromo-tetrafluoropropan-3-ol with an alkaline or alkaline earth metal hydroxide solution, a compound which is 2,3,3,3-tetrafluoro-1,2-epoxypropane, and partially fluorinated polyethers of formula [OCRR.sub.1CR.sub.2R.sub.3].sub.n wherein n is from 5 to 100, R is F or H, R.sub.1 is CF.sub.3, R.sub.2 is F or H and R.sub.3 is H.

Claims

1. A method for preparing a tetrafluoro-1,2-epoxypropane comprising reacting 3-acetoxy-2-bromo-1,1,1,2-tetrafluoropropane or 3-acetoxy-2-bromo-1,1,1,3-tetrafluoropropane with sulphuric acid in an aqueous solution to provide a 2-bromo-tetrafluoropropan-3-ol wherein the 2-bromo-tetrafluoropropan-3-ol is selected from the group consisting of 2-bromo-1,1,1,2-tetrafluoropropan-3-ol, 2-bromo-1,1,1,3-tetrafluoropropan-3-ol, and combination thereof, and reacting the 2-bromo-tetrafluoropropan-3-ol with an alkaline or alkaline earth metal hydroxide solution to provide a tetrafluoro-1,2-epoxypropane.

2. The method according to claim 1, further comprising reacting 1234yf or 1234ze with N-bromosuccinimide in a solution of acetic acid and sulphuric acid to provide the 3-acetoxy-2-bromo-1,1,1,2-tetrafluoropropane or 3-acetoxy-2-bromo-1,1,1,3-tetrafluoropropane.

3. A method for preparing a 2-bromo-tetrafluoropropan-3-ol comprising reacting 3-acetoxy-2-bromo-1,1,1,2-tetrafluoropropane or 3-acetoxy-2-bromo-1,1,1,3-tetrafluoropropane with sulphuric acid in an aqueous solution to provide a 2-bromo-tetrafluoropropan-3-ol wherein the 2-bromo-tetrafluoropropan-3-ol is selected from the group consisting of 2-bromo-1,1,1,2-tetrafluoropropan-3-ol, 2-bromo-1,1,1,3-tetrafluoropropane-3-ol, and combination thereof.

4. The method according to claim 3, further comprising reacting 1234yf or 1234ze with N-bromosuccinimide in a solution of acetic acid and sulphuric acid to provide the 3-acetoxy-2-bromo-1,1,1,2-tetrafluoropropane or 3-acetoxy-2-bromo-1,1,1,3-tetrafluoropropane.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1: Shows the GC mass spectral analysis of a sample of the reaction mixture of Example 4a taken 1 hour after the KOH addition was completed.

(2) FIG. 2: Shows the region in the GC mass spectral traces where 2,3,3,3-tetrafluoro-1,2-epoxy propane eluted, sampled at intervals during the progress of the reaction.

(3) FIG. 3: Shows the .sup.19FNMR spectrum of 2,3,3,3-tetrafluoro-1,2-epoxy propane obtained in Example 4b.

(4) FIG. 4: Shows the .sup.19FNMR spectrum of poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) obtained in Example 4b.

(5) FIG. 5a: Shows the regions of the .sup.19FNMR spectrum of poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) obtained in Example 4b in 1234yf that contained resonances associated with the CF.sub.3 groups, the spectra of 1234yf and the polymer alone are included for reference.

(6) FIG. 5b: Shows the .sup.19FNMR spectrum of poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) obtained in Example 4b in E-1234ze.

(7) FIG. 6a: Shows the .sup.19FNMR spectrum of 1,3,3,3-tetrafluoro-1,2-epoxy propane in the trifluoromethyl region as used in Examples 5a and 5b.

(8) FIG. 6b: Shows the .sup.19FNMR spectrum of poly(1,3,3,3-tetrafluoro-1,2-epoxy propane) in the trifluoromethyl region obtained in Example 5a.

(9) FIG. 6c: Shows the .sup.19FNMR spectrum of poly(1,3,3,3-tetrafluoro-1,2-epoxy propane) 30 in the trifluoromethyl region obtained in Example 5b.

(10) The invention will now be illustrated by the following non-limiting examples.

EXAMPLES

Example 1: Bromo-Oxidation of Tetrafluoropropene to Form Acetoxy-Bromo-Tetrafluoropropane: Synthesis of 3-acetoxy-2-bromo-1,1,1,2-tetrafluoropropane

(11) N-bromosuccinimide (57.2 g, 0.322 mol) was added to a 500 mL flask fitted with a condenser and thermometer. Excess concentrated acetic acid (247 mL) and concentrated sulphuric acid (0.1 equivalents, 0.0322 mol) were added at room temperature. The mixture was stirred and heated to 80° C. 1234yf was then bubbled intermittently into the solution from a pressure cylinder via a flow controller, over a 5 day period until the reaction had turned a very pale yellow. Once the reaction had cooled to 60° C. it was transferred to a separating funnel and diluted with deionised water. The clear oil was separated, and the aqueous layer was washed twice with ether. The combined organics were washed with saturated NaHCO.sub.3, dried with MgSO.sub.4, filtered under vacuum and concentrated affording the acetyl-bromohydrin in 21% yield (25.94 g, 0.103 mol) C.sup.13NMR (DMSO): δ=168.9, 120.9, 98.6, 63.0, 20.5; F.sup.19NMR (DMSO): δ=0.5, −58.1 MS: m/z 43.0, 73.0, 173.0, 253.0

Example 2: Hydrolysis of Acetoxy-Bromo-Tetrafluoropropane to Form Bromo-Tetrafluoropropanol: Synthesis of 2-bromo-1,1,1,2-tetrafluoropropan-3-ol

(12) Concentrated sulphuric acid (3.4 mL, 0.0638 mol) and deionised water (34.4 mL) were added to a 50 mL three-necked round-bottom flask fitted with a condenser. 3-Acetoxy-2-bromo-1,1,1,2-tetrafluoropropane (12.84 g, 0.051 mol) was added with stirring at room temperature. The reaction was heated to reflux for 24 hours. Once cooled the contents were transferred to a separating funnel and extracted twice with ether, the combined organics were washed with saturated NaHCO.sub.3, dried with NaSO.sub.4, filtered and concentrated affording the alcohol in 68% yield (7.3 g, 0.0346 mol). C.sup.13NMR (DMSO): δ=120.6, 101.1, 64.0; F.sup.19NMR (DMSO): δ=0.03, −58.2; MS: m/z 69.0, 159.9, 189.9, 209.9.

Reference Example 3: Ring Closing of Bromo-Fluoropropanol to Form Fluorinated Epoxypropane: Synthesis of 1,1,1-trifluoro-1,2-epoxypropane

(13) 2-bromo-1,1,1-trifluoropropan-3-ol (10 g, 0.0524 mol) was placed in a 2-necked round bottom flask fitted with a distillation set up and then heated to 95° C. Sodium hydroxide (3 g, 0.0754 mol) was dissolved in water (12 g) at 0° C. with stirring. Once the solution was homogenous it was then added dropwise to the 2-bromo-1,1,1-trifluoropropan-3-ol with rapid stirring via dropping funnel. As the head temperature reached 60° C. clear liquid was collected in a receiver flask (4.2 g). GC area %: 1,1,1-trifluoro-1,2-epoxypropane (52%), 2-bromo-3,3,3-trifluoropropene+ethyl ether (26%), 3-acetoxy-2-bromo-1,1,1-trifluoropropane (7%), acetone (2%), unknown (13%).

Example 4a: Ring Closing of 1,1,1,2-tetrafluoro-2-bromopropanol to Form 2,3,3,3-tetrafluoro-1,2-epoxypropane

(14) 1,1,1,2-tetrafluoro-2-bromopropanol (20 g, 0.095 mol) was placed in a 3 necked round bottomed flask along with diethyl ether (40 g). This solution was stirred and cooled to between 0-5° C. in an ice bath and then aqueous potassium hydroxide (6.26 g KOH in 13 g water) was added dropwise over approximately 1 hour. The mixture was stirred for a further 7 hours. A sample was withdrawn 1 hour after the KOH addition was complete and analysed by GC-MS. The presence of 2,3,3,3-tetrafluoro-1,2-epoxy propane in the reaction mixture was confirmed based on mass spectral analysis of the species that eluted prior the diethyl ether solvent, see FIG. 1.

Example 4b: Ring closing of 1,1,1,2-tetrafluoro-2-bromopropanol to Form 2,3,3,3-tetrafluoro-1,2-epoxy Propane and its In Situ Polymerisation to poly(3,3,3,2-tetrafluoro-1,2-epoxy Propane)

(15) 1,1,1,2-tetrafluoro-2-bromopropanol (8 g, 0.038 mol) was placed in a 3 necked round bottomed flask along with petroleum ether (40-60, 21 g) and 2-3 drops of Aliquat 336. The solution was brought to reflux (45° C.) and then aqueous sodium hydroxide (1.6 g NaOH in 20 g water) was added dropwise over approximately 1 hour. The mixture was kept at reflux for a further 6 hours and samples of the organic layer were periodically withdrawn for analysis by GC-MS and .sup.19F NMR spectroscopy. FIG. 2 shows the region in the GC traces where 2,3,3,3-tetrafluoro-1,2-epoxy propane eluted. At the end of the experiment unreacted 2,3,3,3-tetrafluoro-1,2-epoxy propane in petroleum ether solution was obtained by distillation from the reaction mixture and was analysed by .sup.19F NMR spectroscopy. The .sup.19F NMR spectrum of 2,3,3,3-tetrafluoro-1,2-epoxy propane is shown in FIG. 3.

(16) By these methods it was shown that the desired product 2,3,3,3-tetrafluoro-1,2-epoxy propane was formed and built up in the petroleum ether layer but under the high temperature/basic conditions that prevailed began to polymerise and form poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) in situ.

(17) The poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) product was obtained from the reaction mixture distillation residue as a viscous yellow oil following water washing and extraction into dichloromethane, yield 3.24 g (66%). The .sup.19F NMR spectrum of the polymeric product is illustrated in FIG. 4, which shows broad, complex signals characteristic of polymeric materials.

(18) The resulting polymeric oil was found to be soluble in 1234yf and E-1234ze, confirming its utility in heat transfer compositions comprising 1234yf and/or E-1234ze.

(19) Solutions of poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) in 1234yf were prepared and analysed by .sup.19F NMR spectroscopy, the region of their NMR spectra that contained resonances associated with the CF.sub.3— groups in these species are illustrated in FIG. 5a. For reference, spectra of 1234yf and the polymer alone are also included.

(20) Solutions of poly(2,3,3,3-tetrafluoro-1,2-epoxy propane) in E-1234ze were prepared and analysed by .sup.19F NMR spectroscopy, as showed in FIG. 5b.

Example 5: Polymerisation of 1,3,3,3-Tetrafluoro-1,2-epoxy Propane

(21) 5a: Potassium t-Butoxide Initiator

(22) The initiator (2 g) was weighed into a 100 ml capacity autoclave along with solvent (THF, 52 g) and 1,3,3,3-Tetrafluoro-1,2-epoxy propane (30 g). The autoclave was sealed and the contents heated to 100° C. with stirring for 7 hours. After cooling the contents were recovered and the solvent removed in vacuo. The residual oil was dissolved in dichloromethane and the solution washed with water before being dried over anhydrous sodium sulphate. Removal of the solvent in vacuo afforded a viscous yellow oil. The .sup.19F NMR spectrum of the oil is illustrated in FIG. 6b along with that of the starting material for comparison.

(23) 5b: Sulphuric Acid Initiator

(24) 1,3,3,3-Tetrafluoro-1,2-epoxy propane (23 g) was added to a 50 ml round bottomed flask equipped with a dry ice condenser containing the initiator (98% wt, 1 ml). The resulting mixture was stirred for 7 hours and then the excess epoxide was distilled off. The resulting oily residue was washed with water and extracted into diethyl ether. The ether solution was dried over anhydrous sodium sulphate and the ether removed in vacuo yielding a viscous red coloured oil. The .sup.19F NMR spectrum of the oil is illustrated in FIG. 6c along with that of the starting material for comparison.