Patent GB-774103-A (GB)
Title: Halogenated organic compounds
IPC: C07C17/26
Filed: 1952-09-15
Abstract: A method of building up longer chain molecules comprises bringing together polyhalogeno-hydrocarbon starting molecules having at least two carbon atoms and having a terminal carbon atom -->C-Z, where Z represents a chlorine, bromine or iodine atom which is at least as reactive as any other halogen atom present, the terminal carbon having also attached thereto either (a) one or two halogen atoms of no greater atomic weight than Z, or (b) more than one carbon of which at least one bears two or three halogen atoms of lesser atomic weight than iodine and of no greater atomic weight than Z, and subjecting the starting molecules either to energization so that they form free radicals by detachment of the Z atom or to the action of a dehalogenating metal, whereby the starting molecules are dehalogenated to remove intermolecularly a molcule of the halogen Z and thereby the terminal carbon atom of one molecule is coupled to the terminal carbon atom of another molecule.  The starting compounds may have the formula: <FORM:0774103/IV(b)/1> where R and R1 are hydrocarbon or halogenohydrocarbon groups, X is hydrogen or halogen, Y is halogen, and Z is preferably bromine or iodine but may be chlorine.  The starting compound may also have the formula: <FORM:0774103/IV(b)/2> where R, R1 and R11 are hydrocarbon or halogenohydrocarbon, although R11 may be hydrogen, with the proviso that at least one thereof contains at least two halogen atoms of lesser atomic weight than iodine which are attached to a carbon atom linked directly to the carbon atom in the formula.  The resulting products of the coupling have the formula RCXYCXYR, RR1CYCYRR1, RR1R11CCRR1R11, RCX-YCYRR1, RCXYCCRR1R11 or RR1CYCRR1-R11.  The coupling may be achieved by heating, by irradiation with infra-red, visible or ultraviolet light, or with radio-chemical radiation, preferably in the presence of a halogen acceptor, such as Zn, Mg, Sn, Fe, Cd, Hg, NaOH, KI, Na2S2O3, or RSNa where R is an organic radical. The coupling may also be achieved by reacting the starting compounds with Zn, Mg, Sn, Fe, Al, Cu or Cd.  The substituents in the molecules being coupled may be alkyl, halogenoalkyl, alkenyl, halogenalkenyl, cycloalkyl, halogenocycloalkyl, cycloalkenyl, halogenocycloalkenyl, aryl or halogenoaryl groups; acyclic aliphatic and halogenoaliphatic groups containing not more than 20 carbon atoms, and alicyclic and halogenoalicyclic groups containing up to 6 cyclic carbon atoms, are preferred.  Methods are described for the preparation of the starting compounds, such as by addition of halogen compounds, particularly iodine monochloride or monobromide, to suitable unsaturated compounds.  The compounds prepared by themethod of the invention may be subjected to dehalogenation and/or dehydrohalogenation to obtain unsaturated compounds.  Lists are given of starting compounds, compounds prepared by the method of the invention, compounds prepared by subsequent intramolecular dehalogenation and/or dehydrohalogenation, and mercury compounds also obtained when the coupling is carried out with mercury; the mercury compounds have the formul : <FORM:0774103/IV(b)/3> In examples: (1) iodine monochloride is added to chlorotrifluoroethylene to form 1,2-dichloro1,2,2-trifluoroidoethane, which is converted by intermolecular deiodination with mercury to 1,2,3,4-tetrachlorohexafluorobutane, which in turn is converted by intramolecular dechlorination with zinc dust to hexafluorobuta-1,3-diene; (3) iodine bromide is added to chlorotrifluoroethylene to form 1-bromo-2-chloro-1,1,2-trifluoroiodoethane, which is coupled by deiodination with mercury to form 1,4-dibromo-2,3-dichlorohexafluorobutane, which in turn is debrom- and dechlorinated with zinc to give hexafluorobuta-1.3-diene; (4) 1,1-dichlorodifluoroethylene is reacted in separate operations with iodine monochloride and iodine monobromide to give 1,1,2 - trichloro - 2,2 - difluoroiodoethane and 1 - bromo - 2,2 - dichloro - 1,1-difluoroiodoethane respectively, each product being coupled separately by deiodination with mercury to give 1,2,2,3,3,4-hexachlorotetrafluorobutane and 1,4 - dibromo - 2,2,3,3-tetrachlorotetrafluorobutane respectively, the former giving 2,3-dichlorotetrafluoro-buta-1,3-diene on dechlorination with zinc; (5) 1,1,2-trichlorofluoroethylene is reacted with iodine monochloride to form 1,1,2-tetrachloro-1-fluoroiodoethane, which is coupled by deiodination with mercury to give 1,4-difluoro-octachlorobutane, which gives 1, 2, 3, 4-tetrachlorodifluorobuta-1,3-diene on dechlorination with zinc; (6) iodine monochloride is added to 1,2 - dichlorodifluoroethylene, the resulting 1,1,2 - trichloro - 1,2 - difluoroiodoethane being coupled to give 1,1,2,3,4,4 - hexachlorotetrafluorobutane, which is dehalogenated to 1,4-dichlorotetrafluorobuta - 1,3 - diene; (7) CF2ClCCl2I is coupled with CFCl2CC2I to give CF2ClCCl2CCl2CFCl2 which is dechlorinated to 1,2,3-trichlorotrifluorobuta-1,3-diene; (8) CF2ClCCl2 is coupled with CF2ClCFClI to give 1,2,2,3,4 - pentachloropentafluorobutane, which is dechlorinated to 2-chloropentafluorobuta1,3-diene; (9) CFCl2CCl2I is coupled with CF2ClCFClI to give CF2ClCFClCCl2CFCl2 whic is dechlorinated to 1,2-dichlorotetrafluorobuta1,3-diene; (10) CF2ClCFClI is coupled with CFCl2CFClI to give CF2ClCFClCFClCFCl2, which is dechlorinated to 1-chloropentafluorobuta - 1,3 - diene; (11) CF3(CH3)CHCFClI is coupled with CF2ClCFClI to give CF3(CH3)CHCFClCFClCF2Cl which is dehydrochlorinated with alcoholic potassium hydroxide to CF3(CH3)C = CFCFClCF2Cl which is dechlorinated to CF3(CH3)C = CFCF = CF2; (CF3)2CHCFClI is also coupled with CF2ClCFClI, dehydrochlorinated and dechlorinated to give (CF3)2 = CFCF = CF2.