Patented Feb. 15, 1938 2,108,427 Ow UNITED STATES PATEN orrlcl-z 2,108,427 PREPARATION OF ALPHA, BETA UNSATU RATED 'KETON ES Albert Bernard Boese, Jr., Pittsburgh, Pa., as signor to Carbide and Carbon Chemicals Cor poration, a corporation of New York ' No Drawing. Application May 8, 1936, Serial No. 78,661 . ‘ 11 Claims. (o1. 260-131) The invention relates to the production of Example I alpha, beta unsaturated ketones by condensing diketene with aromatic or aliphatic aldehydes To 20.6 grams of. propionaldehyde were added having at least two carbon atoms in the molecule. 29.9 grams of diketene.‘ No initial reaction was observed. After standing at room temperature 5 According to the invention, the selected alde 5 hyde and diketene preferably are mixed and re for 24 hours, the reaction mixture was heated acted in approximately equimolecular propor under reflux for 2% hours. The odors of propion tions. The liquid mixture is heated and refluxed aldehyde and diketene disappeared, and the at the boiling point for-a number of hours. solution became dark. A loss of weight of 15 10 Completion of the reaction usually may be deter grams occurred. The product then was frac mined by the disappearance of the odor of the tionally distilled under atmospheric pressure, and diketene and that of the aldehyde. The reaction the fraction boiling between 128° and 131° C. mixture then is fractionated, generally under at atmospheric pressure was separately con either atmospheric or subatmsopheric pressure, densed and recovered. It contained 21 grams of propylidene acetone, ‘thereby providing a yield of and the fraction containing the unsaturated 15 ketone is separately condensed and recovered. 60.2%. Propylidene acetone is a colorless liquid The unsaturated ketone evidently is produced having an odor characteristic of higher unsatu by the condensation of the aldehyde with diketene rated'ketones. It has a composition correspond to form a ketol, followed by the elimination of ing to the formula CH3CH2CH=CHCOCH3. 20 the elements of water from the latter. This in Example [I 20 turn is followed by the reaction of the resultant product withiwater to form a substituted aceto To 80.4 grams of butyraldehyde was added 94 acetic acid, which then loses carbon dioxide, grams of diketene. A slight exothermic reaction yielding the unsaturated ketone. _ occurred and the solution became pale yellow. These reactions occur concurrently, apparently The solution was cooled and held at room tem in accordance with the following general equa perature for two days. It then was heated under 25 tions, in which R designates a simple or a sub re?ux for two days, at the end of which time stituted alkyl, aryl, or aralkyl group: the odors of butyraldehyde and diketene had vanished, and a loss of weight of 56 grams had 30 (1) RCHO+ CH3COCH=C=O—> occurred. The reaction product then was frac-i RCHOHCH2COCH=C =0 tionated through a two-foot helix-packed column (2) RCHOHCH2COCH=C=O+ with an electrically-heated jacket and controlled RCH=CHCOCH=C=O +H2O re?ux. The fraction boiling between 155°-and (3) RCH=CHCOCH=C:O+H2O~> 160° C. at atmospheric pressure was separately RCH=CHCOCH2COOH condensed and recovered. It contained 69 grams 35 35 (4) RCH=CHCOCH2COOH~> of butylidene acetone, ' RCH: CHCOCH3+CO2 The aldehyde and diketene may be reacted, if desired, in the presence of a volatile solvent non corresponding to a yield of around 55%. 40 reactive with the aldehyde and diketene, among Butylidene acetone is a colorless liquid having which solvents may be mentioned ketones such a characteristic unsaturated ketone odor. It as acetone and methyl ethyl ketone; ethers such rapidly decolorizes bromine water. as dioxan, dimethyl ether, diethyl ether, and Example III isopropyl ether; aromatic and aliphatic hydro 45 carbon, such as benzene, toluene and ligroin; and To 42 grams of diketene were added 50 grams chlorinated solvents such as ethylene dichloride of 2-ethylbutyraldehyde. The resulting solution, and trichlorethylene. after standing at room temperature for 24 hours.v Preferably the mixture of reactants is allowed was heated under reflux for another 24 hours. to stand for a number of hours at room tempera A decrease in weight of 20.4 grams occurred, due 50 ture before re?uxing the mixture, since under to loss of CO2: and the odor of diketene disap such conditions the aldol reaction apparently peared. The mixture then was, distilled under ' proceeds more nearly to completion before the ' atmospheric pressure; and the fraction boiling dehydration occurs. See Equations (1) and (2). within the range from 182° to 190° C. under that The following examples will serve to illustrate pressure was separately recovered. It contained 55 the invention: 40 grams of Z-ethylbutylidene acetone, 55 2 2,108,427 cmcmcn<cmocn=cncocm mately equimolecular proportions oi.’ diketene and corresponding to a yield oi‘ 57.1%. an aldehyde having. at least two carbon atoms Pure 2-ethylbutylidene acetone is a colorless in its molecule, iractionally distilling the result liquid. ant reaction mixture, and separately condensing and recovering a fraction containing an alpha, Example IV beta unsaturated ketone. ' A solution of 27 grams of diketene and 34.1 5. Process which comprises mixing diketene grams of benzaldehyde in 25 cc. of dioxan was and an aldehyde having at least two carbon atoms heated under re?ux for 45 hours, during which in its molecule, maintaining the mixture in the time carbon dioxide was evolved. The solution cold for a substantial period of time, then heat 10 darkened, and a loss in weight of 14 grams oc ing and re?uxing the mixture, tractionally dis curred. The reaction mixture then was frac tilling the resultant reaction mixture, and sep tionally distilled under vacuum. There were arately condensing and recovering a fraction -. obtained 18 grams of unreacted benzaldehyde, 7 containing an alpha, beta unsaturated ketone. grams of a liquid boiling at 120° to 125° C. under 6. The process of making an alpha, beta un 15 10 mm. of mercury absolute pressure, and 21 saturated ketone, which comprises reacting grams of a non-distillable residue. diketene with an aldehyde corresponding to the The fraction which boiled at 120° to 125° C.' formula RCHO, wherein R designates either a under 10 mm. of mercury absolute pressure was simple or a substituted alkyl, aryl, or aralkyl redistilled at atmospheric pressure, and yielded group wherein the substituted group is inert 20 6 grams of benzylldene acetone, in the form of a to diketene, fractionally distilling the resultant liquid boiling at 258° to 263° C. under atmospheric reaction mixture, and separately recovering the pressure, and which, on standing, solidi?ed to a said alpha, beta ‘unsaturated ketone present in colorless solid which melted at 42° to 44° C. the latter. _‘ and had the usual properties of this compound. 7. The process of making an alpha, beta un It is_ within the purview of the invention to saturated ketone, which comprises ‘maintaining - employ, in place of the aldehydes mentioned in at approximately room temperature for a. sub these examples, other aliphatic or aromatic alde stantial period of times. mixture containing ap» hydes having more than ‘two carbon atoms in ‘proximately equimoleculargproportions -of- dike 30 the molecule, such as valeraldehyde, hexaldehyde, tene and an aldehyde corresponding to the for‘ heptaldehyde; and other substituted aldehydes. mula RCHO, wherein R designates ‘either a.- sim wherein each substituting group is'inert-toward _ pie or asubstituted=alkyl,.aryl,~or aralkylgroup diketene, such as 2-ethylhexaldehyde. wherein-the substituting group is inert to ‘dike In general, it appears that the yield of alpha, tene, thereafter heating-and re?uxing ‘the said beta unsaturated ketones is improved in instances mixture, fractionally ‘distilling thev resultant re 35 where the mixture of reactants is permitted to action mixture,- andseparately recovering the stand in the cold or-around room temperature for said alphabets. unsaturated ketone present in " at ‘least several hours. before heating the re a 'the. latter. actants. '- ' . 8. The process of making propylidene-acetone', which comprises reacting a mixture containing #10 The alpha, beta unsaturated ketones of- the 40 - present invention, and particularly those of the : diketene. and proplonaldehyde, thereafter frac aliphatic series, are useful as organic solvents, tionally distlllingvtherresultant reaction mixture, 1' and also as intermediates for the preparation of and separately condensing and recovering the saturated ketones and alcohols. fraction boiling between 128° and 131° C. under atmospheric ‘pressure and containing the pro 45 . ‘The term “alpha, beta-unsaturated ketones” 45 _ is used in the speci?cation and claims to desig pylidene acetone. _ _ , ~‘nate ketones in which the double bond is 10- 9. The process of making 2-ethylbutylidene cated between the alpha and beta carbon atoms. acetone, which comprises reacting a mixturecon I claim: taining diketene and 2-ethylbutyraldehyde, thereafter fractionally distilling the resultant re-_ 50 1. Process which comprises reacting diketene 50 with an‘: aldehyde having atv least two carbon 1 action mixture, and separately condensing and ‘ atoms in its molecule, and recovering an alpha, recovering the fraction boiling between 182° beta unsaturated ketone from the resultant re and 190° C. under atmospheric pressureand con— ‘ action mixture. ' ' taining the 2-ethvlbutylidene acetone. 2. Process which, comprises reacting diketene 10. Process of _ making benzylidene acetone, with an aldehyde having at least two carbon which comprises heating and reacting diketene as ' atoms in its molecule, fractionally distilling the with benzaldehyde, fractionally distilling the re resultant reaction mixture, and separately con sultant reaction mixture, and separately recover densing and recovering the fraction containing ing the benzylidene acetone therein boiling at 258° to 263° C. under atmospheric pressure.