Process for preparing fluorinated conjugated olefinic products

Abstract: The present invention relates to a process for preparing fluorinated conjugated olefinic products having, among others, the formulae: wherein: R x and R y represent, among others, perhaloalkyl radicals containing from 1 to 10 carbon atoms (in the case of R x ) and from 1 to 9 carbon atoms (in the case of R y ), and m ranges from 2 to 10. These olefinic products are obtained by reacting telomeric products having, among others, the formulae: R x O-(CFCl-CFCl) m -F R x O-(CFCl-CFCl) m -OR x F-(CFCl-CFCl) m -F and R y -(CFCl-CFCl) m -F with zinc powder at temperatures of from about 40°C to about 160°C and in a solvent selected from alcohols, dimethylformamide and dimethylsulfoxide. Many of the resulting products are new.

Description: The present invention relates to a process for preparing conjugated fluorinated olefinic products and to the new products obtainable thereby. US-A-3,046,304 is directed to the coupling of halogenated compounds and the use thereof for the preparation of, e.g., halogenated alkenes (such as fluorinated and chlorinated olefins). It also describes the dehalogenation of corresponding halogenated alkanes by means of zinc powder. US-A-2,777,004 describes the preparation of hexafluorobutadiene from symmetrical dichlorodifluoroethylene by dechlorination with zinc powder. US-A-2,745,885 discloses the dechlorination of 1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane with zinc to yield 1-chloro-1,2,3,4,4-pentafluoro-1,3-butadiene. US-A-2,894,042 is concerned with the preparation of hexafluorobutadiene through the reaction of 1,2,3,4-tetrachloroperfluorobutane with zinc. According to CS-A-200,953 (Chem. Abstr. vol. 98, no. 16, 18 April 1983, abstract no. 126788e) polyenes are produced by dehalogenation of α,ω-dibromochlorofluoroalkanes with zinc powder. It is one object of the present invention to provide an economically advantageous process for the preparation of certain perfluorinated conjugated olefins. Another object of the present invention is the provision of fluorinated conjugated olefins which show perhaloalkoxy groups and/or perhaloalkyl groups and/or chlorine atoms at one or both ends of the molecule. These and other objects are achieved by means of the process according to the present invention, according to which fluorinated conjugated olefinic products are obtained which have the formulae: R x O-(CF=CF) m -F (A) R x O-(CF=CF) m -OR x (B) R x O-(CF=CF) m -Cl (E) R y -(CF=CF) m -OR x (I) wherein: R x is a linear or branched perfluoroalkyl radical having from 1 to 10 carbon atoms; R y is a linear or branched perhalogenated alkyl radical, a perhaloalkyl-monoether radical or a perhaloalkyl-polyether radical having from 1 to 9 carbon atoms and containing fluorine atoms or fluorine and chlorine atoms; and m ranges from 2 to 10. The present process is characterized in that telomeric products having the formulae R x O-(CFCl-CFCl) m -F (A') R x O-(CFCl-CFCl) m -OR x (B') R x O-(CFCl-CFCl) m -Cl (E') R y -(CFCl-CFCl) m -OR x (I') wherein R x , R y and m have the meanings specified above, are reacted with zinc powder at temperatures of from about 40°C to about 160°C, preferably from about 40°C to about 100°C, and in a solvent selected from (preferably C₁₋₆) alcohols, dimethylformamide, dimethylsulfoxide. When an alcohol is used as solvent, it may be selected from, for example, methanol, ethanol, propanol, isopropanol, isobutanol and mixtures thereof. The reaction is usually carried out in the presence of a dechlorination activator known from the prior art, for example, KI or NaI. A known agent, which acts as neutralizer of the possibly developed acidity such as, for example, K₂CO₃ or Na₂CO₃ is also commonly employed. The reaction is suitably carried out at the reflux temperature of the solvent. The telomeric products to be used as the starting materials can be prepared by means of a process disclosed in EP-A-348980. The disclosure of said application is incorporated herein by reference. According to said process, 1,2-dichloro-1,2-difluoroethylene is reacted, at a temperature of from -100°C to +50°C, with a perhalofluorooxy compound of formula R x -OF wherein R x has the meanings given above. Thereby, a mixture of telomers having different end groups and different degrees of telomerization is obtained. In practising the above process, a gaseous stream of perhalofluorooxy compound, diluted with an inert gas, is usually fed to a reactor charged with 1,2-dichloro-1,2-difluoroethylene (in the liquid state or dissolved in an inert solvent). By using particular working conditions (such as, for example, the addition of F₂ to the reaction medium), the prevailing production of telomers with certain end groups and with an either comparatively low or a relatively high degree of telomerization can be favoured. When the telomerization reaction is carried out in the absence of F₂ and R x contains one carbon atom, the telomeric products of formulae (A') and (B') are prevailingly formed among others whereas, when R x contains two or more carbon atoms, products of formulae (A'), (B') and (I') are among the predominant ones. When the telomerization reaction is carried out in the presence of F₂, under particular conditions and at temperatures of from -100°C to about -60°C, the same telomeric products are obtained, with products (A') being among the predominant ones. When the telomerization reaction is carried out in the presence of F₂, under different conditions and at temperatures of from about -60°C up to about -20°C, species of formula (E') are obtained, among others, together with those of formulae (A'), (B') and (I'). In the process according to the present invention the mixture of telomeric products is, preferably, used in the same state as it is obtained in, so that a mixture of fluorinated conjugated olefinic products which have a varying degree of telomerization, coincident with the telomerization degree of the starting products, is obtained at the end of the reaction. As long as the degree of telomerization does not exceed 5, the individual olefinic products can be separated from one another by distillation. In the telomeric products used as starting materials as well as in the olefinic products obtained, R y preferably contains two oxygen atoms in case it represents perhaloalkyl-polyether radicals. R y preferably represents perfluorinated radicals. Preferably, R x contains from 1 to 6, particularly from 1 to 3, and R y contains from 1 to 5, particularly from 1 to 3, carbon atoms. When R y contains chlorine atoms, it preferably does not comprise any -CCl₃ or -CFCl-CFCl- groups. In both the starting products and the end products, m preferably ranges from 2 to 5. The olefinic products obtainable by means of the process according to the present invention may be used as comonomers for the preparation of polymers. These polymers, by having been obtained from conjugated olefins, may contain double bonds in the branches of the main chain (backbone) of the polymer. Such double bonds can form sites for crosslinking or other kinds of reactions. The presence of -OR x or R y groups results in polymeric products with properties different from those of polymers obtained from perfluorinated conjugated olefins not carrying such groups. Furthermore, the present olefinic products may be used for the preparation of dielectric fluids and heat exchange fluids. In the process according to the present invention the ratio of gram-atoms Zn to the gram-atoms of units of the formula -CFCl-CFCl- is usually within the range of from 1.00 to 1.5, and preferably of from 1.00 to 1.05. The molar ratio of Zn to activator compound, calculated on the basis of KI, generally ranges from 10 to 37. The molar ratio of Zn to agent for the neutralization of acidity, calculated on the basis of K₂CO₃, is generally within the range of from 4 to 13. In the process according to the present invention, in addition to the fluorinated conjugated olefinic products small amounts of non-conjugated, chloro-fluorinated olefinic products may be formed, which products contain, for example, the sequence -CFCl-CF=CF-CFCl- The desired fluorinated conjugated olefinic products can easily be separated from the above chloro-fluorinated products by distillation. When the process according to the invention is carried out with a mixture of telomeric products obtained by means of the use of CF₃OF (as telogen) in the reaction described in EP-A-348980 mentioned above, which mixture is predominantly composed of the following telomeric species: F-(CFCl-CFCl) m -F (IIIa) CF₃O-(CFCl-CFCl) m -F (Ia) and CF₃O-(CFCl-CFCl) m -OCF₃ (IIa) the following olefinic products will prevailingly be formed: F-(CF=CF) m -F (IIIf) CF₃O-(CF=CF) m -F (If) and CF₃O-(CF=CF) m -OCF₃ (IIf) The species (If) and (IIf) are new products. The product (IIIf), with m equal to 2, is perfluorobutadiene. When a mixture of telomeric products, obtained by means of the use of CF₃CF₂OF as telogen in the telomerization reaction and primarily composed of the following telomeric species: CF₃CF₂O-(CFCl-CFCl) m -F (Ic) CF₃CF₂O-(CFCl-CFCl) m -OCF₂CF₃ (IIc) CF₃-(CFCl-CFCl) m -F (IIIc) CF₃-(CFCl-CFCl) m -OCF₂CF₃ (IVc) and F-(CFCl-CFCl) m -F (IIIa) is used as starting material, the following olefinic products will prevailingly be formed: CF₃CF₂O-(CF=CF) m -F (I′c) CF₃CF₂O-(CF=CF) m -OCF₂CF₃ (II′c) CF₃-(CF=CF) m -F (III′c) CF₃-(CF=CF) m -OCF₂CF₃ (IV′c) The species (I′c), (II′c), (III′c) and (IV′c) are new products. When a mixture of telomeric products obtained by means of the use of CF₃-CF₂-CF₂-OF as telogen in the telomerization reaction and predominantly composed of the following telomeric species: CF₃CF₂CF₂O-(CFCl-CFCl) m -F (Id) CF₃CF₂CF₂O-(CFCl-CFCl) m -OCF₂CF₂CF₃ (IId) CF₃CF₂CF₂O-(CFCl-CFCl) m -OCF₂CF₃ (IIId) and F-(CFCl-CFCl) m -F (IIIa) is used as starting material, the following olefinic products will prevailingly be formed: CF₃CF₂CF₂O-(CF=CF) m -F (I'd) CF₃CF₂CF₂O-(CF=CF) m -OCF₂CF₂CF₃ (II'd) CF₃CF₂CF₂O-(CF=CF) m -OCF₂CF₃ (III'd) and F-(CF=CF) m -F (III'f) The species (I'd), (II'd) and (III'd) are new products. The main advantages of the present invention can be summarized as follows: New fluorinated conjugated olefins, which show perhaloalkoxy groups and/or perhaloalkyl groups at one or both ends of the molecular chain, may be obtained. The following examples are given in order to illustrate the present invention without limiting it. EXAMPLE 1 The mixture of telomers used as starting material was prepared as follows: A gaseous stream of 0.6 Nl/hour of fluorooxy-trifluoromethane, 0.6 Nl/hour of F₂ and 103 Nl/hour of N₂ was bubbled through 450 g of liquid 1,2-dichloro-1,2-difluoro-ethylene (DCDFE), cooled to -72°C in a reactor equipped with condenser, thermometer and stirrer. After 18 hours the reaction was discontinued and unreacted DCDFE was distilled off. 105 g of product were recovered, which product was analysed by gas-chromatography on a 3% SP 2100 column, gas mass and ¹⁹F-N.M.R. spectroscopy. The product was composed prevailingly of the following species: CF₃O-(CFCl-CFCl) m -F (Ia) CF₃O-(CFCl-CFCl) m -OCF₃ (IIa) and F-(CFCl-CFCl) m -F (IIIa) The species in which m is 2 constituted 98% by weight of the mixture. Those in which m is 3 accounted for about 2% of the mixture. Based on 100 g of mixture, the species were distributed as follows: (IIIa) = 87 g (Ia) = 4.8 g (IIa) = 3.6 g A reactor equipped with thermometer, stirrer, dropping funnel and collection and rectification system was charged with 210 ml of dimethylformamide and, subsequently, 50 g of Zn powder, 10 g of K₂CO₃ and 7 g of KI were added thereto. Thereupon, 100 g of the above telomeric mixture were successively introduced within 4 hours. The dechlorination reaction started at a temperature of 40°C. During the dropwise addition the temperature was kept from exceeding 60°C. Upon completion of the addition the reaction was completed by maintaining the reaction mixture at 55 to 60°C for 1 hour and then at about 68°C for a further hour. During the feeding of the telomers and the completion of the reaction, 31 g of the component of formula F-(CF=CF)₂-F i.e., perfluorobutadiene, were collected in the reactor rectification system. At the end of the perfluorobutadiene collection the residual reaction mixture was subjected to fractional distillation. Collected were: 0.5 g of CF₃O-(CF=CF)₂-OCF₃ in the form of three positional isomers; Traces of CF₃O-(CF=CF)₂-F in the form of 2 positional isomers; 0.7 g of CF₃O-CF=CF-CCl=CF₂ in the form of 3 positional isomers. The reaction products were analysed by gas-chromatography on a 1% SP 1000 column, gas mass and ¹⁹F-N.M.R. spectroscopy. The isomers of formula CF₃O-CF=CF-CCl=CF₂ result from the presence, in the telomers used as the starting products, of isomers of formula CF₃O-CFCl-CFCl-CFCl=CF₂. EXAMPLE 2 The mixture of telomers used as the starting product (100 g) was prevailingly composed of the following species: a) F-(CFCl-CFCl) m -F 30.4 g b) CF₃O-(CFCl-CFCl) m -F and CF₃O-[(CFCl-CFCl) m-½ -CHF]-F, totalling 26.5 g c) CF₃O-(CFCl-CFCl) m -OCF₃ 31.5 g and d) CF₃O-(CFCl-CFCl) m-1 -CCl=CF₂ 9.4 g. The species in which m is 2 constituted 95% by weight of the mixture. Those in which m is 3 accounted for 5% of said mixture. A reactor equipped with thermometer, stirrer, dropping funnel and collection and rectification system was charged with 210 ml of dimethylformamide and, subsequently, 50 g of Zn powder, 10 g of K₂CO₃ and 7 g of KI were added thereto. Thereupon, 100 g of the above telomeric products were successively introduced within 4 hours. The dechlorination reaction started at 40°C and the temperature was kept from exceeding 60°C. Upon completion of the feeding step the reaction was completed by maintaining the reaction mixture at 55 to 60°C for 1 hour, and then at 68°C for a further 1.5 hours. Already during the introduction of the telomers and also during the completion of the reaction 11.1 g of perfluorobutadiene were collected in the reactor rectification system. After the collection of the perfluorobutadiene the residual reaction mixture was subjected to fractional distillation. Collected were: 6.1 g of CF₃O-(CF=CF)₂-F in the form of 2 positional isomers; 12.1 g of CF₃O-(CF=CF)₂-OCF₃ in the form of 3 positional isomers; 9.2 g of CF₃O-CF=CF-CCl=CF₂ in the form of 3 positional isomers. The products obtained were analysed by the methods described in example 1. EXAMPLE 3 The mixture of telomers used as starting material (60 g) was prevailingly composed of the following species: a) F-(CFCl-CFCl) m -F 25.4 g; b) CF₃-(CFCl-CFCl) m -F CF₃O-[(CFCl-CFCl) m-½ -CHF]-F and CF₃O-(CFCl-CFCl) m-1 -CCl=CF₂, totalling 19.3 g; c) CF₃O-(CFCl-CFCl) m -OCF₃ 12.1 g. The species in which m is 2 constituted about 99% by weight of the mixture. A reactor equipped with thermometer, stirrer, dropping funnel and collection and rectification system was charged with 150 ml of isobutanol and, subsequently, 31.5 g of Zn powder, 6.5 g of K₂CO₃ and 3.5 g of KI were added thereto. Thereupon, 60 g of the above telomeric mixture were sucessively introduced within 3 hours. The dechlorination reaction started at a temperature of 85°C. After the reaction the temperature was caused to decrease to about 60°C. After the feeding of the telomers, the reaction was completed by maintaining the reaction mixture at 65 to 70°C for 1 hour, and then at a maximum temperature of 80°C for a further 1.5 hours. During the introduction of the telomers and during the completion of the reaction, 8.5 g of perfluorobutadiene were collected. When the collection of perfluorobutadiene was completed, the residual reaction mixture was subjected to fractional distillation. Collected were: 6.1 g of CF₃O-(CF=CF)₂-F in the form of 2 positional isomers; 2.1 g of CF₃O-CF=CF-CCl=CF₂ in the form of 3 positional isomers; 2.85 g of CF₃O-(CF=CF)₂-OCF₃ in the form of 3 positional isomers. The products obtained were analysed by the methods described in example 1.

Claims: Fluorinated conjugated olefinic products having one or more of the formulae: R x O-(CF=CF) m -F (A) R x O-(CF=CF) m -OR x (B) R x O-(CF=CF) m -Cl (E) R y -(CF=CF) m -OR x (I) wherein: R x is a linear or branched perfluoroalkyl radical having from 1 to 10 carbon atoms; R y is a linear or branched perhaloalkyl, perhaloalkyl-monoether or perhaloalkylpolyether radical having from 1 to 9 carbon atoms and containing fluorine atoms or fluorine and chlorine atoms and m ranges from 2 to 10. Products according to claim 1, wherein R x contains from 1 to 6 carbon atoms and R y contains from 1 to 5 carbon atoms. Products according to one or more of the preceding claims wherein m ranges from 2 to 5. Process for preparing the products according to claim 1, wherein products having the formulae R x O-(CFCl-CFCl) m -F (A') R x O-(CFCl-CFCl) m -OR x (B') R x O-(CFCl-CFCl) m -Cl (E') R y -(CFCl-CFCl) m -OR x (I') wherein R x , R y and m are defined as in claim 1, are reacted with zinc powder at temperatures of from about 40°C to about 160°C and in a solvent selected from alcohols, dimethylformamide and dimethylsulfoxide. Process according to claim 4, characterized in that the alcoholic solvent is selected from methanol, ethanol, propanol, isopropanol and isobutanol. Process according to claim 4 or 5, characterized in that the reaction is carried out in the presence of a dechlorination activator. Process according to one or more of claims 4 to 6, characterized in that the reaction is carried out in the presence of an agent which acts as neutralizer of acidity.

Inventors: FIORANI TIZIANA, MARACCINI ANTONIO, PASQUALE ANTONIO, FIORANI, TIZIANA, MARACCINI, ANTONIO, PASQUALE, ANTONIO
Applicants: AUSIMONT SPA, AUSIMONT S.P.A.
Application year: 1989
Main classification: C07C43
IPC codes: C07C67, C07C41, C07C43, C07C21, C07C17