United States Patent 0 " 1C6 Patented Apr
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3,657,310 United States Patent 0 " 1C6 Patented Apr. 18, 1972 1 2 3,657,310 Carbonates of the above type are useful as lubricants PROCESS FOR MAKING ALIPHATIC and hydraulic ?uids, and as plasticizers for vinyl resins, CARBONATE ESTERS ethylcellulose, and other synthetic resins. Ludo K. Frevel, Midland, Mich., assiguor to The Dow Chemical Company, Midland, Mich. ‘DETAILED DESCRIPTION ‘OF THE INVENTION No Drawing. Filed Aug. 14, 1969, Ser. No. 850,215 The starting materials used in the invention, the ester Int. Cl. C07c 67/00, 67/02, 69/00 salts of the formula ROCOOM, are of a well-known US. Cl. 260-463 5 Claims class and are conveniently made by the reaction of CO2 With the appropriate alkali metal alcoholate, ROM. The 10 latter is readily made by reaction of the alcohol, ROH, ABSTRACT OF THE DISCLOSURE with alkali metal or with the hydroxide, alkoxide or Esters of the formula amide of an alkali metal. Techniques for conducting these reactions are well known. In a preferred process, at least >ROCOO(A-0)n ' a one molar excess of alcohol is used to make the alco wherein R and R’ are anonovalent aliphatic radicals, A holate. The resulting alcohol solution of alcoholate, with is an alkylene radical of 2-4 carbon atoms and n is an or without dilution with inert solvent, is then reacted integer at least ‘1, are made by ' with CO2 to make the carbonate ester-salt. The alcoholic ‘(1) Reacting an alkali metal bicarbonate ester with solution or dispersion of ester-salt is then reacted with methyl chloride, bromide or iodide: methyl chloride, bromide or iodide to produce, at least transiently, the methyl ester, ROCOOCH3. The latter ROCO>OM+CH3X—>ROCOOCH3+MX then reacts with the excess alcohol to produce the de wherein M is alkali metal and X is Cl, Br or I, and sired ester, thus effectively combining the methylation and (2) Reacting the above methyl ester with a mono transesteri-?cation steps.~ ' ether of an alkylene glycol or polyglycol: The alkali metal may be Li, Na, K, Rb, or Cs, the pre ferred ones being ‘N a and K. The alcohol, ROH, may be an al'kanol, preferably a lower alkanol (up to about ‘6 carbon atoms) or a mono ‘In a preferred process, step 1 is conducted in the pres— ether of a glycol or polyglycol having the formula ence of the glycol ether, thus combining the two steps. 30 wherein R’, A and n are as de?ned above. Examples of suitable such alcohols include methanol, butanol, hexanol, I BACKGROUND OF THE INVENTION Z-ethylbutanol, isobutanol, 2-methoxyethanol, 2-butoxy 'Dialkyl carbonates have been made by the reaction ethanol, l-isobutoxy-Z-propanol, the monomethyl, ethyl, of an alcohol with phosgene and by the reaction of KZCOS 35 butyl and hexyl ethers of di-, tri-, tetra- and pentaethyl with alkyl halide (Fukui et al., CA, 58, 2366). ene, -propylene and -butylene glycols. Certain glycol ether carbonates have been described The glycol or polyglycol monoether used in the last by ‘Drake et al., J.A.C.S., 52, 3720. step of the process may be any of those de?ned above CROSS-REFERENCES TO RELATED having the formula R’(OA)nOI-I. APPLICATIONS 40 The reaction of the ester-salt with the methyl halide is conveniently conducted at about l00°-170° C. and My copending application with lDavid F. Gransden, under at least the autogenous pressure of the reaction Ser. No. 784,266, ?led Dec. 16, ‘1968 discloses the prepa mixture. The reaction time may vary widely, depending ration of certain glycol ether carbonates by the alcoholy on temperature and reactants, but is ordinarily about sis of diethyl carbonate. 45 1-10 hr. 1My copending application with Jo Ann Gilpin, Ser. No. The proportion of methyl halide to ester-salt is not 798,765, ?led Feb. 12, 1969, discloses the preparation critical, though as a practical matter at least a molar of certain glycol ether carbonates by alcoholysis of cyclic equivalent should be used. alkylene carbonates. In the transesteri?cation reaction, at least a molar SUMMARY OF THE INVENTION equivalent of the alcohol, R’(OA),,OH, should be used to insure substantial reaction. Removal of the by-product Carbonate esters of the formula methanol also favors completion of the reaction. When ROCO>O(AO)n ' the alcohol corresponds to the R of the methyl ester, are made by: i.e., when R is the same as R(OA),,—, the ?nal product (1) Reacting an alkali metal bicarbonate ester with 55 is a symmetrical ester and a large excess of alcohol in methyl chloride, bromide or iodide: the transesteri?cation can do no harm. However, when the ?nal product is to be an unsymmetrical ester, the ROCOOM +OH3X—> ROCOOCH3 +MX use of a large excess of alcohol will tend to displace not and only the methyl group of the intermediate ester but also (2) Reacting the methyl ester produced in step (1) 60 the R group thereof, thus producing the symmetrical with a monoether of an alkylene glycol or polyalkylene ester R’(OA),,‘OCO(OA)nR'. The formation of this by glycol: product ester can be largely suppressed by (1) using only the stoichiometric amount or only a slight excess of alcohol in the transesteri?cation and (2) terminating the 65 reaction no later than when substantially the calculated wherein, in all the above formulas, R is lower alkyl or amount of methanol has been produced. —-(AO),,R', and R’ is lower alkyl, i.e., up to about ‘6 car While some transesteri?cation goes on during the meth 'bon atoms, X is Cl, Br or I, M is an alkali metal, A is an ylation reaction, it is usually desirable to raise the tem alkylene radical of 2-4 carbon atoms and n is an integer perature and/or remove methanol as formed in order at least ‘1 and may be as much as 5 or more. to complete this step after methylation is complete. As will be shown hereinafter, the above two steps can Temperatures of 125°-l70° C. are generally preferred. be combined into a single step. No additional catalyst is necessary under these condi 3,657,310 4 tions. For most purposes the residual catalyst should be toluene azeotrope was distilled at atmospheric pressure separated from the product before the latter is used. over a period of 3.5 hr., thereby removing 57.7 g. of While the above reactions can be conducted without water, 142 g. of toluene and 2.3 g. of the alcohol. The use of inert solvent, especially when a substantially ex sodium salt was then carbonated with 43 g. of CO2 to cess of alcohol is used, it is preferred to use enough yield the sodium bicarbonate ester of 2(2-methoxy solvent to ?uidize the reaction mixture and serve as a ethoxy) ethanol. 7 dispersing medium for the insoluble salts. Suitable such A portion (64 g.) of the slurry‘ thus obtained contain solvents include hydrocarbons, such as petroleum ether, ing 0.11 m. of sodium 2(2-methoxyethoxy)ethyl carbon kerosine, benzene, toluene and xylene; ethers such as ate was transferred to a glass ampoule and CH3Br (12.75 diisopropyl ether, tetrahydrofuran, dioxane, the dimethyl 10 g.) was added. The ampoule was sealed and heated at ethers of ethylene glycol and diethylene glycol and the 100° C. for 10 hr. in a rocking bomb. The ampoule was like. cooled and opened and the liquid contents after sepa SPECIFIC EMBODIMENTS ration of NaBr were distilled to produce 13.4 g. of the The following examples illustrate the practice of the desired carbonate. invention. I claim: EXAMPLE 1 1. The process comprising (a) reacting a compound of the formula Dimethyl carbonate ROCO'OM Metallic sodium 1(0.35 g., 0.015 m.) was dissolved in 3.21 g., 0.1 m., of methanol. The solution was cooled 20 with methyl chloride, bromide or iodide, thus to to ~80° C. and 2 g. of CO2 was added. The container produce a methyl ester of the formula was sealed and heated at 100° C. for 1 hr. The excess ROCOOCH3 CO2 was then vented and 1.56 g. (0.031 m.) of CH3Cl and was added, the container was sealed and heated 2 hr. (b) reacting the methyl ester with an alcohol of the at 150° C. The reactor was then cooled and the excess 25 formula CHaCl (1.31 g.) was distilled 01f, leaving a methanolic HO (A0)n ' solution of the product, the composition of which was determined by infrared absorption. Excluding the metha thus to produce an ester of the formula nol, it contained 92% of dimethyl carbonate. ROCOO(AO),,R' 30 EXAMPLE 2 where in all the above formulas, R is lower alkyl or --(AO)nR', R’ is lower alkyl, A is an alkylene Bis(2-(2-methoxyethoxy)ethyl) carbonate radical of 2-4 carbon atoms, M is an alkali metal Metallic sodium (0.6 g., 0.026 m.) was dissolved in and n is an integer 1-5. 11.87 g., 0.1 m. of 2(2-methoxyethoxy)ethanol. To the 2. The process of claim 1 wherein step (a) is con resulting solution was added 1.10 g. of CO2 at 25° C. ducted in the presence of the alcohol HO(AO)nR', thus and 5 p.s.i.g. The resulting thick slurry was diluted with combining steps '(a) and (b) into a single unit process. 1.7 g. of CH3Cl, sealed, and heated at 150° C.