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United States Patent (19 11, 3,923,914 Kobetz Et Al United States Patent (19 11, 3,923,914 Kobetz et al. 145 Dec. 2, 1975 54 CHEMICAL PROCESS OTHER PUBLICATIONS 75 Inventors: Paul Kobetz; Kenneth L. Lindsay, both of Baton Rouge, La. Technique of Organic Chemistry, Vol. VII, pp. 244, 249, Weisberger, Interscience Publishers, London 73) Assignee: Ethyl Corporation, Richmond, Va. (1955). 22 Filed: July 2, 1973 (21 Appl. No.: 375,871 Primary Examiner-Delbert E. Gantz Assistant Examiner-Joseph A. Boska Attorney, Agent, or Firm-Donald L. Johnson; John F. I52) U.S. Cl.............................................. 260/658 R Sieberth; Edgar E. Spielman, Jr. 51) Int. Cl.’.......................................... CO7C 17/20 58) Field of Search ................................. 260/658 R 56) References Cited (57) ABSTRACT UNITED STATES PATENTS A process is disclosed for preparing dibromomethane 2,553,518 5/1951 Lake et al....................... 260/658 R from the reaction of, in the presence of an inert sol 2,675,413 4/1954 Ballard et al.................... 260/658 R vent, alkali metal bromide and dihalomethane. FOREIGN PATENTS OR APPLICATIONS 10 Claims, No Drawings 1,127,345 9/1968 United Kingdom............. 260/658 R 3,923,914 2 the production of dibromomethane from the reaction CHEMICAL PROCESS of dichloro or chlorobromomethane and alkali metal bromide was fraught with difficulty as the equilibrium BACKGROUND OF THE INVENTION of the reaction(s) was shifted far to the left. It has now Brominated hydrocarbons are very valuable com been discovered that the equilibrium of the reaction(s) pounds as they are truly of a multipurpose nature. For can be shifted far to the right by the utilization of a example, methylene bromide may be used as an ingre unique solvent which results in high alkali metal bro dient in fire extinguishing fluids or as a fire retardant; it mide utilization, i.e., up to 60 percent. also may be used as a fluid for gauges and as a heavy Generally speaking, the solvent utilized in the pro liquid in solid separations based upon differences in O cess of this invention may be described as a solvent specific gravity. which is inert to the reaction mixture and which is ca Recognizing the unique value of brominated hydro pable of substantially dissolving the reactants and the carbons, many processes for their production have brominated hydrocarbon products while not substan been developed. U.S. Pat. No. 1,891,415 discloses a tially dissolving the alkali metal chloride by-product. method wherein bromine is reacted with aluminum in a 15 By not substantially dissolving the alkali metal chloride closed system to form molten aluminum bromide which as it is produced it is theorized, though this invention is is then fed directly into reaction with a chlorinated hy not limited to this theory, that the reaction(s) are drocarbon to form the brominated product. This driven to the right. A particularly useful solvent has method, however, suffers from the disadvantage that been found to be one which comprises monoalkyl ether undesirable sludge is formed during the reaction of the 20 of alkylene glycol and water. Preferred monoalkyl aluminum bromide with the chlorinated hydrocarbon. ethers of alkylene glycol for this solvent are those in The formation of sludge is avoided by the method of which the alkyl constituent contains up to three carbon U.S. Pat. No. 2, 120,675 wherein the aluminum bro atoms and in which the alkylene constituent(s) likewise mide is dissolved in an inert solvent such as ethyl bro contain up to three carbon atoms. Exemplary of such mide prior to feeding the solution into reaction with the preferred glycols are monoethyl ether of diethylene chlorinated hydrocarbon. This process, even though it glycol, monopropyl ether of triethylene glycol, mono avoids sludge formation, has the undesirable feature ethyl ether of ethylene glycol, monoethyl ether of prop that a large proportion of inert solvent is employed ylene glycol, monoethyl ether of tripropylene glycol, which reduces the productive capacity of a reactor of monopropylene ether of dipropylene glycol, mono any given size. Further, this reaction suffers from the 30 methyl ether of ethylene glycol, monomethyl ether of disadvantage that it tends to stop far short of complete dipropylene glycol and the like. Most highly preferred consumption of one or both reactants presumably be glycols are monoethyl ether of ethylene glycol and cause of a chemical equilibrium between the reactants monoethyl ether of diethylene glycol. and the products. The volume ratio of the monoalkyl ether of alkylene U.S. Pat. No. 2,553,518 discloses the production of 35 glycol to the water is preferably within the range of organo bromine compounds by reacting hydrogen bro from about 1:1 to about 3:1. Other volumetric ratios mide and centain chlorinated organic compounds in outside of this preferred range, however, may also be the presence of an aluminum halide or borohalide cata used. The main consideration in selecting the volumet lyst. This method is said to overcome the problems ric ratio is whether or not that particular ratio will en mentioned in the earlier two processes; however, this 40 able the reactants and brominated products to be in so process utilizes a catalyst which requires replacing and lution while causing the alkali metal chloride by-pro a hydrogen bromide reactant which is corrosive to con duct to be out of solution as a precipitate. Determina ventional equipment. tion of any particular ratio therefore is easily achieved Therefore, it is an object of this invention to provide by simple tests utilizing the before mentioned criteria a catalyst free process for the production of dibromo 45 of solubility as the determinative factor of whether or methane which does not suffer from any of the above not a particular volumetric ratio is desirable. mentioned disadvantages and which utilizes readily The amount of solvent used in the process of this in available, noncorrosive, inexpensive reactants. vention should be that amount which dissolves the re actants and brominated products while at the same THE INVENTION 50 time maintaining the alkali metal chloride out of solu This invention relates to a process for the production tion as a precipitate. Generally speaking, the amount of of dibromomethane by the reaction of alkali metal bro solvent used will be within the range of from about 1 ml mide and dihalomethane in the presence of an inert Sol to about 20 ml of solvent per gram of reactant used. vent comprising monoalkyl ether of alkylene glycol and Illustrative of the benefits realized when practicing water, wherein at least one of the halogens in the diha 55 the process of this invention with its unique solvent are lomethane is chlorine and the remaining halogen is ei shown in Examples I and II. Examples III and IV are not ther chlorine or bromine, and wherein the alkali metal of this invention and illustrate the low yields realized in the alkali metal bromide has an atomic number when not practicing the process of this invention. greater than 3. EXAMPLE I When the dihalomethane is dichloromethane in the 60 process of this invention the following equilibrium re To a small test tube was added 1.0 g NaBr, 2.0 cc actions take place: CH(OCHCH)OH, 1.0 cc HO and 0.4 g CHCl. 1. CHCl, + MBr streng. CHCIBr + MCIJ The tube was then sealed so as to prevent evaporation 2. CHCIBr +MBratru,CHBr, + MCl of any of the ingredients during the reaction period. wherein M is an alkali metal having an atomic number 65 The sealed tube was then placed in an oil bath at 140°C greater than 3. If the dihalomethane is chloro for 1%hours. After this period of time the tube was bromomethane then equilibrium reaction (2) occurs. cooled to room temperature. The seal of the tube was Prior to the discovery of the process of this invention broken and the ingredients removed. A sodium chlo H 3,923,914 3 4 ride precipitate was noticed and was removed by filtra an excess in the amount of alkali metal bromide being tion. The remaining solid-free filtrate was subjected to preferred. Alkali metal bromide quantities which are NMR analyses. The analysis showed that the dihalome about two times the stoichiometric amount are highly thane content was 15 mole percent CHBr, 55 mole preferred as such amounts aid in keeping the reaction percent CHCIBr, and 35 mole percent CH.Cl. This equilibrium shifted to the right. yield represents a 42.5 percent conversion of sodium No particular order of addition for the reactants is bromide. required. For example, the alkali metal bromide may be added to the dihalomethane used or vice versa with EXAMPLE II no criticality being found. The reactants and solvent The procedure of Example I was followed except that () should be added and thus mixed together at room con 1.0 NaBr, 0.3 g CHCl, 2.0 cc CHOCHCHOH, and ditions as the dihalomethanes are liquid at these condi 1.0 cc HO was added to the test tube. By the analysis tions and are therefore easy to handle. After the reac it was shown that the dihalomethane content com tants have been added, one to the other, and the appro prised 32 mole percent CHBr, 45 mole percent priate reaction conditions are achieved, a reaction per CH.ClBr, and 37 mole percent CH.Cls. This yield cor 15 iod of from about/3 to about 5 hours should be allowed responds to a 54.5 percent conversion of the sodium so as to enable the reactions to reach equilibrium. bromide used. After the reaction has reached equilibrium, it may be desired to recover the methylene bromide in essentially EXAMPLE III pure form.
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