Patent GB-873222-A (GB)
Title: Perhalocyclobutane-1,2-diones and their preparation
IPC: C08G75/02
Filed: 1959-04-13
Abstract: Tetrahalo-1, 2-cyclobutanediones (see Group IV(b)) are homopolymerized, or copolymerized with compounds of the same type or with other monomers capable of addition polymerization.  The halogen atoms in the dione compound may be fluorine, chlorine, or bromine atoms and they may be all alike or different. Polymerization may take place without the presence of any added initiator and at temperatures below room temperature.  The diones may be copolymerized with monomers capable of forming co-polymers by free-radical mechanisms, e.g. those containing ethylenic and acetylenic linkages, or with monomers capable of forming co-polymers by anionic means e.g. styrene, vinylidene cyanide, or acrylonitrile, or those monomers wherein the molecules contain at least one oxygen or sulphur atom e.g. cyclic ethers and compounds containing carbonyl or thiocarbonyl groups such as aldehydes and ketones.  In the case of polymerization by freeradical means the polymers are probably acyclic and have the structure of 2, 2, 3, 3-tetrahalosuccinoyl units, but in the case of polymerization by anionic means, the polymers have a plurality of recurring cyclic structures and may be regarded as polyoxy (3, 3, 4, 4-tetrahalo-2-oxocyclobutylidene) compounds.  The polymers may be used in powder or shaped form e.g. as blocks, films, or fibres, as adsorbants for protonic substances such as water, alcohols, and amines.  This adsorbency is probably due to chemical action, the molecules of the protonic substance becoming attached at the ketonic groups of the polymer and forming hydrates, hemiketals, or similar addition compounds.  In an example, 3, 3, 4, 4-tetrafluoro-1, 2-cyclobutanedione is mixed under reduced pressure with anhydrous diethyl ether in a reactor which is cooled to -78 DEG C.; nitrogen is introduced and the pressure allowed to rise to atmospheric; dimethylformamide in anhydrous ether is added and the temperature is allowed to rise to 0 DEG C.; a solid white polymer which is regarded as a polyoxy (3, 3, 4, 4-tetrafluoro-2-oxo-cyclobutylidene) is obtained.  This polymer may be treated with ethyl alcohol, and after the exothermic reaction has subsided, the solution is heated at 65 DEG -75 DEG C., filtered, and dried under high vacuum to obtain the ethanol adduct as a light yellow powder.  The formation of the yellow colour is an indication of the presence of the protonic reactant i.e. ethyl alcohol, and the diketone polymer may therefore be used as an indicator for the hydrogen ion.  In another example, a copolymer is obtained by reacting 3, 3, 4, 4-tetrafluoro-1, 2-cyclo-butanedione with thiocarbonyl difluoride in the presence of a solution of dimethyl formamide in anhydrous ether in a glass reactor swept with a stream of gaseous helium and cooled to -78 DEG C. A white solid (thiodifluoromethylene)-[oxy(3, 3, 4, 4-tetrafluoro-2-oxycyclobutylidene)] copolymer is obtained. Specification 620,296 is referred to.ALSO:The invention comprises perhalocyclobutane-1,2-diones, and hydrates and hemiketals thereof, of the general formula: <FORM:0873222/IV (b)/1> <FORM:0873222/IV (b)/2> wherein the X's which may be the same or different, are fluorine, chlorine, or bromine atoms, and the R's, which may also be the same or different, are hydrogen atoms or monovalent hydrocarbon (including alkyl, alkenyl, aryl, and cycloalkyl) or monovalent polyfluorohydrocarbon radicals.  The diones may be prepared by strong acid hydrolysis of the corresponding perhalocyclobutane-1,2-diethers, e.g. the 1,2-bis(hydrocarbonoxy)-1,2,3, 3,4,4-hexahalocyclobutanes. The diethers may themselves be obtained by thermal dimerization, i.e. cycloaddition, of the corresponding perhalovinyl ethers and these may be obtained by reacting the appropriate sodium or other alkali metal alcoholate or phenolate with tetrafluoroethylene.  The perhalocyclobutane-1,2-diether intermediates may also be obtained by direct halogenation of perhalocyclobutene-1,2-diethers.  In an example, sodium methoxide, dioxane, tetrafluoroethylene, and a terpene stabilizer, are heated at 80 DEG C. in a sealed reactor to obtain methyl trifluorovinyl ether, which is isolated by fractional distillation and then placed in glass reactors which have been cooled in a bath of liquid nitrogen.  A small proportion of phenothiazine and of a terpene stabilizer are added and the reactors are sealed and heated to 150 DEG C. to obtain 1,2-dimethoxy-hexafluorocyclobutane, which is isolated by fractional distillation and then reacted with concentrated sulphuric acid to obtain a hydrate of perfluoro-1,2-cyclobutanedione.  The hydrate is cooled in a solid carbon dioxide/acetone bath, mixed with phosphorus pentoxide, and then heated under reduced pressure to 200 DEG C. to obtain perfluoro-1,2-cyclobutanedione.  The hydrate forms spontaneously from the diketone in the presence of moisture. Alkaline oxidation of the hydrate results in the production of 2,2,3,3-tetrafluoropropionic acid.  Phosphoric acid may be used instead of sulphuric acid for the hydrolysis of the hexahalo-1,2-cyclobutane diethers.  Liquid organic diluents may be present during the formation of the diethers and during the strong acid hydrolysis.  The production of 3,4-dichloro-3,4-difluoro-1,2-cyclobutanedione; 3,3,4,4 - tetrachloro-1,2-cyclobutanedione; 3,4,4-trichloro-3-fluoro-1,2-cyclobutanedione; 4-bromo-3-chloro3,4-difluoro-1,2-cyclobutanedione; and of perbromo-1,2-cyclobutanedione is described.  The bis- and half-hemiketals are readily formed by direct addition of the diones with stoichiometric proportions of the corresponding alcohol or phenol.  Specified ketals are the dimethyl and diethyl hemiketals of tetrafluoro-1,2-cyclobutanone, the methyl and ethyl half-hemiketals of tetrafluoro-1,2-cyclobutanedione.  The dione may be used as an indicator for determining the quantity of water, alcohol, or other active protonic substance present in an organic medium free from protonic hydrogen.  It may be used as a solution in an anhydrous diluent such as tetrahydrofuran, and added dropwise to the liquid under test until a persistent pink colour is obtained.  The consumption of dione is proportional to the amount of water or alcohol present.  The tetrahalo-1,2-cyclobutanediones may be homopolymerized or co-polymerized with other compounds of the same type or with other polymerizable monomers (see Group IV(a)). Specification 620,296 is referred to.