r: 3,287,425 United States Patent 0 1C6 Patented Nov. 22, 1966

1 2 propanes; acyclic compounds containing one or more car 3,287,425 bon-to-oarbon double bonds such as hexachloropropene, FLUORINATED COMPOUNDS AND THEIR PREPARATION 3-hydropentachloropene, octachlorobutenes, heptachloro John T. Maynard, Brandywine Hundred, Del., assignor to butenes, hexachlorobutenes, hexachloro-1,3-butadiene, and E. I. du Pont de Nemours and Company, Wilmington, perchloro-l,5-hexadiene; saturated carbocyclic compounds Del., a corporation of Delaware such as perchlorocyclopentane and perchlorocyclohexane; No Drawing. Filed Mar. 7, 1961, Ser. No. 93,860 and carbocyclic compounds containing one or two car 14 Claims. (Cl. 260-6533) bon-to-carbon double bond-s in the ring such as octachloro cyclopen-tene. This application is a continuation-in-part of my co 10 As indicated above, the polychlorohyd-rocarbon com pending application Serial No. 12,973, ?led March 7, pounds are added to an agitated suspension of an alkali 1960, now abandoned. metal ?uoride which is either potassium ?uoride, cesium This invention relates to a novel process for preparing ?uoride, or rubidium fluoride. If desired, mixtures of ?uorinated compounds. In addition, this invention re these alkali metal ?uorides may be used. The alkali metal lates to novel 2-hydrohepta?uorobutenes. 15 ?uoride should be ?nely divided and anhydrous. The Fluorine-containing compounds are of great potential amount of alkali metal ?uoride to be used depends upon value for a wide variety of purposes. However, use of the number of chlorine atoms to be replaced in the poly many of these compounds is severely limited because of chlorohydrocarb-on starting material. In order to re the lack of economically practical methods for their prepa place all of the chlorine atoms, at least one mole of alkali ration. This invention provides a continuous process for 20 metal ?uoride should be used per mole of chlorine to the preparation of a variety of ?uorine-containing com be replaced. Preferably, at least 1.1 mole of alkali metal pounds, which method is economically more ‘attractive ?uoride should be used for each chlorine atom to be re than methods heretofore disclosed in the art. placed. A greater amount may be used, but it is usually While the prior art describes various procedures for not necessary to use more than 3 moles of alkali metal preparing ?uorine-containing compounds, in general, these 25 ?oride per mole of chlorine to be replaced. procedures have involved prolonged reaction under rather The solvent which is employed in the process of this severe conditions. vIt is not possible from these dis invention should have a boiling point of at least 150° C. closures to predict the conditions necessary to carry out so that it does not distill out of the reaction mixture and, a continuous process in which the ?uorinated compound of course, should be liquid at the reaction temperature. is removed continuously from the reaction medium. 30 It is preferred that the solvent have a ‘boiling point of ‘It is an object of the present invention to provide a about 10° C. above the temperature of the reaction. novel process for preparing ?uorinated compounds. A Representative solvents which may ‘be used include the further object is to provide novel Z-hydrohepta?uoro lower carboxylic acid amides and preferably those con butenes. A still further object is to provide a process for training from 1 to 4 carbon atoms such as formarnide, the preparation of these Z-hydrohepta?uorobutenes. Other 35 acetamide, propionamide, butyramide, and isobutynamide, objects will appear hereinafter. and their N-alkl or N,N-diaklyl derivatives in which the These and other objects of this invention are accomp alkyl groups are lower alkyl; lower alkyl sulfoxides and lished by a process of continuously preparing ?uorinated sulfones and preferably those containing from 1 to 4 compounds containing at least 3 carbon atoms which com carbon atoms, such as dimethyl sulfone, dimethyl sul prises maintaining at about 150 to 250° C. an agitated 40 foxide, diethyl sulfone, diethyl sulfoxide, dibutyl sulfone, suspension of an alkali metal ?uoride wherein the alkali and dipropyl sulfoxide; cyclic alkylene sulfones, and car metal is selected from the group consisting of potassium, bonates containing from 5 to 6 members in the ring, cesium and rubidium in a solvent having a boiling point such as tetr-amethylene sulfone, pentamethylene sulfone, of at least about 150° C., which solvent is selected from ethylene carbonate, 1,2-propylene carbonate, and 1,3 the group consisting of lower carboxylic acid amides, lower 45 hutylene carbonate; and lactones and lactams containing alkyl sulfoxides, lower alkyl sulfones, cyclic alkylene sul from 5 to 7 atoms in the ring such as 2-pyrrolidone, N fones containing from 5 to 6 members in the ring, cyclic rnethyl-Z-pyrrolidone, caprolactam, 'y-butyrolactone, and alkylene carbonates containing from 5 to 6 members in Z-piperidone. The preferred solvent is N-methyl-Z-pyr the ring, lactones containing from S to 7 atoms in'the rolidone because of its read-y availability and high boiling ring, and lactams containing from 5 to 7 atoms in the 50 point. The amount of solvent to be used is not critical ring; continuously adding to said suspension a polychloro except that su?icient solvent should be present during the hydrocarbon compound which contains at least 3 carbon reaction to suspend the particles of the alkali metal atoms and continuously removing the formed ?uorinated ?uoride and to provide intimate contact of the ?uoride with compound as a vapor; said polychlorohydrocarbon com the polychlorohydrocarbon reactant. pound being. a hydrocarbon compound where at least 50 55 The process is carried out using any conventional equip percent of the hydrogen atoms have been replaced by ment which will provide ‘means for the continuous addi chlorine. tion of the polychlorohydrocarbon starting material to a The novel compounds 2-hydrohepta?uorobutene-2 and slurry or agitated suspension containing the alkali metal Z-hydrohepta?uorobutene-l may be prepared by the ?uoride suspended in the solvent and ‘for the continuous above-described process from ‘hexachloro-1,3-butadiene. 60 removal of volatile products. The solvent-?uoride slurry The polychlorohydrocarbon compounds which are used is ?rst brought to the desired temperature and is main as starting materials in the process of this invention are tained at this temperature during the continuous addition aliphatic and cycloaliphatic hydrocarbon compounds hav of the polyohrlorohydrocarbon reactant. It is preferred ing at least 3 carbon atoms and having at least 50 percent to provide agitation to assure intimate contact of the of the hydrogen atoms replaced by chlorine. Thus, these 65 polychloro'hydroca-rbon reactant with the metal ?uoride. compounds consist solely of carbon, chlorine and, in some Optionally, the solvent-?uoride slurry may also be con~ instances, hydrogen. It is preferred that these polychloro tinuously ‘fed into and withdrawn from the reaction vessel. hydrocarbon compounds contain not more than about 12 A ‘slow sweep of an inert gas such as nitrogen may be carbon atoms. Representative compounds which may passed through the reaction vessel to assist in removal ‘be used include saturated acyclic compounds ‘such as 70 of volatile products. The volatile products may be col octachloropr-opane, heptachloropropanes and hexachloro lected ‘by conventional methods such as by condensation, 3,287,425 3 4. - . solution in a solvent, etc. In some cases it may be de or in combination with other gaseous ?uorinated com sira'ble to maintain the reaction temperature ‘for a short pounds such as dichlorodi?uoro-methane. time after addition of the starting material is complete in The following examples will ‘better illustrate the nature order to recover the maximum amount of ?uo-rinated of the present invention; however, the invention is not product. This is not essential and is usually not necessary. intended to be limited to these examples. Parts are by Although somewhat ' igher or lower temperatures may weight unless otherwise indicated. be used, the reaction is preferably carried out in the range A. The experiments described in Examples 1 to 7 are of about 150° C. to about 250° C. Below 150° C. the conducted by the following method: reaction proceeds too slowly, and temperatures above The reaction is carried out in a ?ask ?tted with an 250° C. are not necessary. The temperature will depend 10 agitator, a gas inlet ‘for a nitrogen sweep, an inlet for con to a certain extent upon the boiling point of the solvent tinuous feed of the polychloro‘hydroca-rbon starting ma— being used. For example, when 'N-methyl-2-pyrrolidone terial, and a Claisen head vented to a series of traps cooled is used as the solvent, a temperature [range of 190-200” C. by solid carbon dioxide. An anhydrous alkali metal may be used. When dimethylformamide is used, as the ?uoride and the solvent are placed in the ?ask. Glass solvent, at temperature of only about 150° C. is attainable. 15 beads (50-150 grams) are added to provide an abrading When temperatures in the lower part of the range are action to expose fresh reaction surfaces. The reaction used, the yield of volatile product may be Somewhat mixture is agitated during the entire process. The re lower than when the higher temperatures are used. The action mixture is heated to the desired temperature and reaction is normally conducted at atmospheric pressure; the temperature is maintained while the po-lychlorohydro however, lower or higher pressures may be used. 20 carbon starting material is introduced continuously The compounds which are obtained as a result of the through the gas inlet. A slow sweep of nitrogen is main process of this invention are ?uorinated materials wherein tained to assist in carrying the volatile products to the the chlorine atoms present in the starting compound have trap system where they are condensed. The evolution been partially or completely replaced by ?uorine. In of product starts essentially immediately and the rate of general, more than 50 percent of the chlorine ‘atoms will 25 evolution depends on the rate of addition of starting 1be replaced by ?uorine. The conversions accomplished material. In many cases evolution of product is essen appear ‘in many cases to be the result of a series of reac tially complete by the time the polyohlorohydrocarbon tions that may include dehydrochlorinati-on, dechlorina addition is stopped. In other cases, heating and nitrogen tion, addition of hydrogen ?uoride and chlorine to double sweep is maintained until evolution of product is com bonds, and direct replacement of chlorine atoms by ?uor 30 plete. ' ine atoms. _ Example 1 The process of the present invention provides a highly The process described in paragraph A is carried out efficient method for the preparation of ?uorinated com_ using the following materials: _ pounds ‘having a wide variety of uses. In many cases the Grams compounds are useful as propellents and refrigerants, Potassium ?uoride ______174 either alone or in combination with other ?uolrinated N-methyl-2~pyrrolidone ______500 hydrocarbons such as di?uorodichloromethan-e. They are Hexachloropropene ______83 'useful as solvents and they may also be used as inter mediates for the preparation of other ?uorine-containing The hexachloropropene is added continuously over a 40 period of two hours while the temperature is maintained compounds. at 190-200“ C. Evolution of volatile products is essen Two of the compounds which may be prepared accord tially complete Within 30 minutes after addition of hexa ing to this invention are the novel compounds 2Jhydr\o— chloropropene is ?nished. The product consists of 28 hepta'fluorobuten-e - 2 and 2 - hydrohepta?uorobutene - 1. parts of a mixture of highly ?uorinated compounds, in These compounds may he represented by the formulae cluding 2,2-dichloroper?uoropropane, 2-chlor0-2-hydro CFg-CHZCF-CP}, and CF2=CH-CF2—CF3 respec 45 tively. These compounds are colorless liquids of low per?uoropropane, and ole?nic components. Analysis of the reaction mixture shows that 80 percent of the chlo boiling points. The structures of these compounds have rine in the starting hexachloropropene has been converted been assigned on the basis of their infrared spectra, nuclear magnetic resonance studies and chemical oxida to chloride ion. tion to known ?uorinated carboxylic acids. From these 50 When, instead of N-methyl-Z-pyrrolidone, one of the studies it also appears that the Z-hydrtrhepta?uo-rob’utene-2 below-listed materials is used as a solvent, in the tempera exists in cis- and trans-isomeric (forms. When these two ture range indicated below, essentially the same products compounds are (freshly prepared, the major portion of are obtained. - ° C. the mixture of isomers ‘distills in the range of 11-15 ° C. 55 at atmospheric pressure. The remainder boils ?rom 15 N,N-dimethylformamide ______ISO-165 18° C. On standing for a few weeks in a stainless steel Dimethyl sulfoxide ______- 150 container, the boiling range changes to 7-10° C. at at Dimethyl sulfone ______150-240‘ mospheric pressure. It is vbelieved that this is the result Tetramethylene sulfone (tetrahydrothiophene, l-dioxide) ______150-200 of isomerization of the Z-hydroheptaiiuoro‘butens-2 from 60 the ois-folrm to the trans-form. Ethylene carbonate (1,3-dioxolane-2-one) _.___ 150-200 The novel Z-hydrohepta?uorobutenes are useful as in Example 2 termediates in the preparation of other ?uoro compounds. The‘process described in paragraph A is carried out For example, they may be chlorinated to yield chloro using the following materials: ?uorobutanes which are stable heat transfer liquids. They 65 Grams may be oxidized to mixtures of tri?uoroacetic acid and Potassium ?uoride ______87 penta?uoropropionic acid. The ‘acids are useful in acylat N-methyl acetamide ______250 ing stericarlly hindered carboxy acids, as solvents for pro Hexachloro-l,3-butadiene ______43.5 teins and as catalysts for hydrolysis of esters. The Z-hy The hexachl0ro-1,3-butadiene is added continuously drohepta?uorobutenes are also useful ‘as inert propellents, 70 during a period of two hours while the temperature is where, because of their molecular con?guration and con maintained at 184-195 ° C. A 33 percent yield of 2-hy sequent difference in solubility, they may advantageously droper?uorobutene-2 is obtained. be substituted 1for the conventional ?uorinated propellents When the experiment is repeated using N,N-dimethyl in many cases. They may also be utilized as gaseous acetamide as the solvent instead of N-methylacetamide dielectrics. They may be used as refrigerants, either alone 75 and a tempearture of about 165° C., a slightly lower yield 3,287,425 5 6 of the 2-hydroper?uorobutene-2 is obtained. A similar Example 7 result is obtained when the process is carried out using The procedure described in paragraph A is carried out formamide as the solvent and maintaining the tempera using the following materials: ture at about 150° C. The different temperatures are necessary because of the differences in the boiling points Grams of the respective solvents. Potassium ?uoride ______116 N-methyl-Z-pyrrolidone ______250 Example 3 1,1,2,2,3,3-hexachloropropane ______54 The process described in paragraph A is carried out The hexachloropropane is added continuously during a period of one hour while the temperature is maintained using the following materials: 10 Grams at 195-200° C. The volatile products are found to con Potassium ?uoride ______116 sist largely of 2,2-dihydrohexa?uoropropane (B.P. 3—5° Dimethyl sulfone ______300 C.) and 2-chloro-1-hydro-tetra?uoropropene (B.P. 17 18° C.). These compounds are identi?ed by means of Hexachloro-l,3-butadiene ______43.5 15 nuclear magnetic resonance spectroscopy. The hexachloro-1,3-butadiene is added continuously Essentially the same results are obtained when 1,1,1, during a period of 70 minutes while the temperature is 2,3,3-hexachloropropane is used as reactant instead of maintained at 190-195” C. After another hour, during 1,l,2,2,3,3-hexach1oropropane. which time the temperature is allowed to rise to 240° C., Example 8 evolution of product is complete. The volatile product collected in the trap system is distilled to give a 51 percent The equipment consists of a reaction vessel equipped yield of Z-hydroper?uorobutene-Z. for distillation with a receiver which in turn is connected to a cold trap cooled with solid carbon dioxide. The reac Example 4 tion vessel is changed with 480 parts of dimethyl form~ The process described in paragraph A is carried out 25 amide, 87 parts of hexachloro-1,3-butadiene and 232 parts using the following materials: of anhydrous potassium ?uoride and then heated at 150° Grams C. while stirring for 51/2 hours. During the last 1% hours, unreacted hexach‘loro-1,3-butadiene and a portion of the Cesium ?uoride ______228 'dimethyl formamide are distilled over into the receiver. N-methyl-2-pyrrolidone ______400 30 From the cold trap, there is recovered 3 parts of a color Hexachloro-1,3-butadiene ______.. 43.5 less liquid miXture of the isomeric 2-hydrohepta?uoro The hexachloro-1,3-butadiene is added continuously butenes. during a period of 75 minutes while the temperature is Example 9 maintained at 195° C. A 58 percent yield of 2-hydr0~ Using the equipment of Example 8, a mixture of 500 per?uorobutene-Z is obtained. 35 parts of N-methyl pyrrolidone, 87 parts of hexachloro Similar results are obtained when rubidium ?uoride is 1,3-butadiene and 232 parts of anhydrous potassium used in place of cesium ?uoride. ?uoride is stirred and heated at 190-200“ C. for 3 hours Example 5 and then 200' parts of the mass is allowed to distill out. From the cold trap there is recovered 28 parts of Z-hydno The process described in paragraph A is carried out 4.0 hepta?uorobutenes. This is a 46 percent yield based on using the following materials: the hexachloro-1,3-butadiene. Grams Example 1 0 Potassium ?uoride ______174‘ N-methyl-Z-pyrrolidone ______450 A reaction vessel is equipped with an addition inlet, Octachloropropane (added as a solution in 75 g. of 45 an agitator, an inlet for sweeping with inert gas, and N-methyl-Z-pyrrolidone) 5 8 an outlet leading to a cold trap cooled with solid carbon dioxide. The reaction vessel is charged with 500' parts The solution of octachloropropane is added continu of N-rnethyl pyrrolidone, and 174 parts of anhydrous ously to the reaction vessel during a 90-minute period potassium ?uoride. About 50 parts of glass beads is while the temperature is maintained at 195-200° C. After 50 added to abrade the potassium ?uoride during agitation. addition of the octachloropropane is complete, tempera The temperature is then raised to ISO-195° C. while ture and nitrogen sweep are continued for an additional agitating. A slow stream of nitrogen is then passed hour, after which time the evolution of product is com through the vessel while 87 parts of hexachloro-1,3-buta plete. The product is largely 2,2-dichloroper?uoropro diene is added slowly and uniformly over a period of 3 pane, having a boiling point of 33° C. and a refractive 55 hours. The 2-hydrohepta?uorobutenes formed are swept index r1332“ 1.3032, which is obtained in about a 60 percent into the cold trap by the nitrogen stream. 34 parts is yield. Analysis of the reaction mixture shows that 79 collected which is a 56 percent yield based on the hexa percent of the chlorine of the starting material is con chlorobutadiene. verted to chloride ion. The products from Examples 9' and 10 are combined Example 6 60 and distilled through a low-temperature column. A major portion distills over a range of 11-15° C. at atmospheric The process described in paragraph A is carried out pressure. Analysis of the nuclear magnetic resonance using the following materials: spectrum of this fraction shows that at least 90 percent Grams of it must have the structure CF3—-CH=CF—CF3. The Potassium ?uoride ______116 65 remainder of the material .distills at 15-18° C. This N-methyl-Z-pyrrolidone ______350 fraction is oxidized with alkaline potassium permanganate Octachlorocyclopentene (added as a solution in 75 and the resulting acids are esteri?ed with ethanol. The grams of N-methyl-Z-pyrrolidone) ______43 mixed esters distill at 66-69“ C. at atmospheric pressure and has a refractive index H1325 1.30160. An infrared The solution of octachlorocyclopentene is added con 70 absorption spectrum shows all the bands typical of ethyl tinuously to the suspension of the salt in the solvent dur tri?uoroacetate and ethyl penta?uoropropionate, both ing a 45-minute period while the temperature is main known compounds. This is clear evidence of the presence tained at 195-200“ C. Evolution of volatile material, of both CF3-CH=CF—CF3 and CF2=CH—CF2—CF3 found to be essentially pure octa?uorocyclopentene, B.P. in the fraction. The nuclear magnetic resonance spec 26.2° C., is complete after an additional 15 minutes. 75 trum of the 11—l5° C. fraction, measured at 40‘ mega 3,287,425 7 8 cycles against tri?uoroacetic acid as a zero standard, 8. A process of continuously preparing ?uorinatcd com shows doublet bands at +620 cycles per second and +39 pounds containing from about 3 to 12 carbon atoms ?rom cycles per second. These are attributed to the presence polychlorinated aliphatic and cycloaliphatic hydrocarbon of two different cFg-groups, each being a doublet because compounds wherein at least 50% of the chlorine atoms of the possibility of cis-/transisomerisrn. A third ?uo thereof are replaced by fluorine atoms which comprises rine peak, due to a single ?uorine atom, is present at maintaining at about 150° to 250° C. an agitated suspen ——l682 cycles per second. These bands account for about sion of an alkali metal ?uoride wherein the alkali metal is 90 percent of the sample and can be attributed to the selected from the group consisting of potassium, cesium and rubidium in a solvent (having a boiling point of at structure CF3—CH=CF-—CF3. v ' least about 150° C., which solvent is selected from the Example 11 group consisting of lower carboxylic acid amides, lower The procedure of Example 10 is repeated except that alkyl sulfoxides, lower alkyl sulfones, cyclic alkylene sul N-methyl aeetamide is substituted for the N-methyl fonescontaining from 5 to 6 members in the ring, cyclic pyrrolidone. A 33 percent yield of 2-hydrohepta?uoro alkylene carbonates containing ‘from 5 to 6 members in butenes is obtained. 15 the ring, lactones containing from 5 to 7 atoms in the ring, When this example is repeated using dimethyl acet and lactams containing .from 5 to 7 atoms in the ring; con amide instead of the N-methyl acetamide, it is necessary tinuously adding to said suspension a polychlorinated to decrease the temperature to 160-165 ‘’ C. because of hydrocarbon compound which contains from about 3 to 12 the lower boiling point of the amide. carbon atoms and continuously [removing the formed ?uor Example 12 20 inated compound as a vapor; said polyohlorinated fhydro carbon compound being an aliphatic or cycloaliphatic Two runs are made in the same Way as Example 10 except the quantities are doubled. The resulting 2-hydro hydrocarbon compound wherein at least 50 percent of heptafluorobutene products are combined and distilled the hydrogen atoms have been replaced by chlorine. as before, collecting the material boiling at 10-l8° C. 9. A process according to claim 8 wherein the alkali The distillate is put in a stainless steel cylinder and set 25 metal ?uoride is potassium ?uoride. 10. A process according to claim 8 wherein the solvent aside for about a month. The product is then redistilled. This time 85 percent of the product distills at 7~8° C. is N-methyl-2-pyrrolidone and the temperature is main tained at about 190 to 200° C. at atmospheric pressure and the balance at 8-10" C. 11. A process according to claim 8 wherein the poly Infrared spectral analysis of the 7-8° C. ‘fraction shows 30 substantially the same pattern as the product which has chlorinated hydrocarbon is hexachloropropene. 12. A process according to claim 8 wherein the poly ' distilled at 10-15° C.- A vapor phase chromatographic analysis of the 7-80 C. fraction shows that it consists of chlorinated hydrocarbon is heXachloro-l,3-butadiene. 13. A process according to claim 8 wherein the poly 95.3 percent of a single component, 2.3 percent of a chlorinated hydrocarbon is octachloropropane. second component immediately adjacent in the elution 35 pattern, and the balance a number of minor impurities. 14. A process according to claim 8 wherein the ‘poly Analogy with other ?uoroole?ns indicates that the major chlorinated hydrocarbon is octachlorocyclopentene. product is the trans-isomer. It is believed that the cis References Cited by the Examiner form, which is ?rst formed, isomerizes on standing. UNITED STATES PATENTS As many widely di?erent embodiments of this invention 40 may be made without departing from the spirit and scope 2,842,603 7/ 1958 Miller ______260-6533 thereof, it is to be understood that‘ this invention _is not 2,918,501 12/1959 Bre'hm et al ______260—-653.3 limited to the speci?c embodiments thereof except as de 2,983,764 5/1961 Knaack ______260—-653.3 ?ned in the appended claims. 3,024,290 3/ 1962 Henne ______260-6533 What is claimed is: 45 1. A compound selected from the group consisting of OTHER REFERENCES Z-hydrohepta?norobutene-Z and Z-hydrohepta?uorobu Fields et al.: Proceedings of the Chemical Society 1960, tene-l. 22, cited in Chemical Abstracts 57, 9637b (1962),. 2. A compound of the formula Houben-Weyl, Methoden Der Organischen Chernie, 50 Georg Thieme Verlag, ‘Stuttgart (1962), vol. 5/3, pp. 153 157. . 3. A compound of the formula Hudl-icky, Chemistry of Fluorine Compounds, The Macmillan Co., New York (1962), pp. 104-110. 4. A process for preparing Z-hydrohepta?uorobutenes Lovelace, Aliphatic Fluorine Compounds, Reinhold which comprises heating ihexao‘hloro-l,Elebutadiene with 55 Pub. Co., New York (1958), pp. 2, 3, 42. potassium ?uoroide in an organic carboxylic acid amide Tullook et al.: J. Org. Chem., vol. 25, pp. 2016-19 solvent ‘at a temperature of from about 150 to 200° C. (1960). 5. A process according to claim 4 wherein the solvent is dimethyl f-orrnarnide. LEON ZITVER, Primary Examiner. 6. A process according to claim 4 wherein the solvent is 60 AL‘PHONSO D. SULLIVAN, Examiner. N-methyl pyrrolidone. 7. A process according to claim 4 wherein the solvent is DANIEL D. HORWITZ, JOSEPH R. LIBERIVIAN, J. \V. N-rnetlhyl acetamide. WILLIAMS, K. V. ROCKEY, Assistant Examiners.