Patented Mar. 14, 1944 2,344,061

UNITED STATES PATENT office 2,344,061 PREPARATION OF 1-CHLORO-1-FLUORO ETHYLENE Mary W. Renoll, Dayton, Ohio, assignor to Mon Santo Chemical Company, St. Louis, Mo., a cor poration of Delaware No Drawing. Application July 19, 1940, Serial No. 346,345 3 Claims. (CI. 260-653) This invention relates to an improved method forth by van de Walle in the Bulletin de l'academie for the preparation of 1-chloro-1-fluoro-ethylene. royale de mediecine de Belgique, pages 94-104. 1-chloro-1-fluoro-ethylene has the formula, (1924). The 1,2-dibromo-2,2-dichloro-ethane, so prepared, Was then treated with hydrogen fluoride in the presence of red mercuric oxide, by a process similar to that described by Henne in the Journal H & of the American Chemical Society, vol. 60, pages and is a colorless gas at room temperature and 1569-1571 (1938). In carrying out this reaction, atmospheric pressure. Its point of liquefaction 217 parts (one molecular proportion) of mercuric is -25.5 C. at a pressure of 741 mm. of mercury 0. Oxide Were added, preferably in successive Small and its freezing point is below -80° C. The poly portions, to Substantially 770 parts (three molecu merization and co-polymerization of this unsatu lar proportions) of 1,2-dibromo-2,2-dichloro rated polymerizable organic compound has been ethane contained in a suitable reaction vessel and described in co-pending application, Serial Num provided with means for agitation. Following the ber 346,346, filed July 19, 1940. 15 addition of each portion of mercuric oxide, an According to my work, 1-chloro-1-fluoro-eth hydrous hydrogen fluoride was introduced into ylene can be prepared, in general, by the removal the reaction mixture until the appearance of of the Substituents represented by X from white mercuric bromide was noted. During this Compounds possessing the general formula, period, the reaction mixture was cooled by a suit CH2X-CXCIF, wherein. One X is a halogen other 20 able method, as for example, by surrounding the than fluorine and the other X is a member of the reaction vessel with ice. After all of the mate group consisting of hydrogen, and a halogen other rials had been added to the reaction vessel, the than fluorine. Illustrative of the materials pos mixture was allowed to stand over night at room Sessing the above described general formula, temperature, and then was poured into ice water CHX-CXCF, that can be employed are 1-bro 25 and the water insoluble product washed by de no-2,2-dichloro-2-fluoro-ethane, 1-chloro-2,2-di cantation. Final purification of the product was chloro-2-fluoro-ethane and 1,2-dichloro-2-fluoro accomplished by suitable means, as for example, ethane. According to the present invention, 1 by steam distillation followed by fractionation chloro-1-fluoro-ethylene may be prepared in high under reduced pressure. yields from 1-bromo-2,2-dichloro-2-fluoro-ethane. 30 The purified product, a colorless liquid, was In the preparation of 1-chloro-1-fluoro-eth found to be 1-bromo-2,2-dichloro-2-fluoro-ethane ylene from compounds possessing the general for and was obtained in a yield of substantially 50%, mula, CHX-CXCF, it has been found that the based on the amount of red mercuric oxide en removal of the Substituents represented by Xcan ployed. This hitherto unknown chemical com be accomplished by methods similar to processes 35 pound was found to possess the following physical previously described in the chemical literature. properties: Thus, where both X's represent halogens other Boiling point-110.8° C. at 760 mm. of mercury than fluorine, a selective dehalogenation treat Freezing point-Solidifies to a transparent solid ment is employed, i. e., a process whereby a halo at liquid air temperatures gen other than fluorine is removed from each 40 Density-d. 18672 Carbon atom, as for example, reaction. With zinc Refractive index-nds 1.4626 in the presence of anhydrous ethanol. On the Other hand, Where One X represents a halogen The 1-bromo-2,2-dichloro-2-fluoro-ethane, so other than fluorine and the other X represents prepared, was then subjected to the action of hydrogen, a selective dehydrohalogenation treat 45 In OSSy Zinc in the presence of anhydrous ethanol ment is necessary. Thus, it has been found that and, preferably, in the presence, additionally, of this reaction can be carried out, for example, by a Small amount of cuprous chloride. In carrying . treatment with alcoholic potassium hydroxide out this reaction, 366 parts of 1-bromo-2,2-di under Suitable conditions. chloro-2-fluoro-ethane, dissolved in an equal vol The following is a specific example illustrative 50 ume of anhydrous ethanol, Were added at a suit of the process of the present invention whereby able rate to a mixture comprising substantially the compound, 1-chloro-1-fluoro-ethylene, can be 130 parts of mossy zinc, a small amount of cuprous prepared, the parts being by weight. First, 1,2- chloride and 60 parts of anhydrous ethanol con dibromo-2,2-dichloro-ethane was prepared from tained in a Suitable reaction vessel. It was found 1,1-dichloro-ethylene according to a process Set 55 preferable to Warm the reaction vesse and to in

2 2,344,061 troduce a small amount of undiluted 1-bromo and one chlorine atom from 1-bromo-2,2-dichlo 2,2-dichloro-2-fluoro-ethane to initiate the reac ro-2-fluoro-ethane by subjecting said compound tion prior to the addition of the alcohol solution to the action of zinc in the presence of anhydrous of 1 - bromo -22- dichloro-2-fluoro-ethane. The ethanol. product of this reaction was distilled out of the 2. Process as defined in claim 1 in which said reaction vessel as formed, condensed and Collected bromine and chlorine atoms are removed by sub in a receiving vessel cooled to a very low tempera jecting said compound to the action of zinc in the ture, for example, to -80' C. presence of anhydrous ethanol and a small The product after purification, for example, by amount of cuprous chloride. re-distillation, was found to be 1-chloro-1-fluoro O , 3. Process as defined in claim 1 in which said ethylene and was obtained in a yield of substan 1-bromo-2,2-dichloro-2-fluoro-ethane is dissolved tially 77%. in anhydrous ethanol and the solution is added to This invention is limited solely by the claims a mixture comprising zinc and a small amount of attached hereto. cuprous chloride in anhydrous ethanol and in What is claimed: 5 which the product of the resulting reaction is dis 1. A process for preparing 1-chloro-1-fluoro tilled out as formed, condensed, and collected. ethylene comprising removing the bromine atom MARY W. RENOLL.