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 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 by condensing diketene with aromatic or aliphatic 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 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 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 , 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