REACTIONS OF KETENE HUGH.J. HAGEMEYER, JR.

Tennessee Eastman Corporation, Kingsport, Tenn.

Ketene and carbonyl compounds can react to form either enol acetates or p-lactones and products thereof, depend- ing on the choice of catalyst and reaction conditions. Enol acetates are formed by reaction of enolizable car- bonyl compounds-that is, a carbonyl compound con- taining at least one available hydrogen atom on a carbon atom adjacent to the carbonyl group-with ketene in the presence of acid esterification catalysts. Acetylsulfo- acetic acid is a preferred enol acetylation catalyst and temperatures in the range 50" to 90" C. are usually em- ployed. Ketene and carbonyl compounds react to form p-lactones and products thereof in the presence of suitable condensation catalysts. The optimum conditions, cata- lysts, and catalyst concentrations vary for individual carbonyl comqounds. The choice of the catalyst and catalyst concentration should be such that maximum rate of reaction is obtained with a minimum formation of diketene. If 0-lactones or decarboxylation products thereof are the desired compounds, the reaction should be conducted at low temperatures, 0' to 10" C., to mini- mize the linear polymerization of the p-lactone. Where the unsaturated acid is the desired product, the reaction is conducted at 40" to 60" C., to ensure the gradual forma- tion of the linear polyester of the p-lactone, which is then depolymerized by distillation.

ETENE, the inner anhydride of acetic acid,ismanufactured K by the pyrolysis of acetic acid and acetone. Commer- cially i t is used principally in the production of acetic anhydride and, to a lesser extent, diketene. The discovery and develop- ment of new catalysts for reactions with ketene have now led to the manufacture of p-lactones and enol acetates from carbonyl compounds and ketene. Staudinger (17) first described the for- mation of @-lactones by condensing diphenylketene with quinone. I n condensations with diphenyllietene, Staudinger used com- pounds containing highly active carbonyl groups such as dibenzyl ketone, quinone, and benzophenone. The condensation reaction was carried out in the absence of catalysts and required elevated temperatures such that the decarboxylation products of the p- lactones rather than the p-lactones themselves were isolated-for example, benzophenone and diphenylketene give tetraphenyl- ethylene and carbon dioxide.

(CeH5)aCO + (CeHJ2 C=C=O + (CeHJz C=C(CoHs)z + GO1

More recently Kung (10) described the condensation of ketene, CHz=C=O, with formaldehyde and acetaldehyde in the presence of Friedel-Crafts type catalysts to form propionolactone and p- butyrolactone, respectively.

CH*=C==O + CHZO/ZnCl% --+ CH2CH2C=0 LOJ

and

CHZ=C=.O + CH&HO/ZnClZ -3 CH,CHCH-C=O L-0-J

A similar condensation with ketene and furfural and ketene and benzaldehyde was reported by Hurd in 1933 (6) in which the p- lactone decarboxylation products, a-vinylfuran and styrene, re- spectively, were isolated.

765

HC-CH H:-~~CHCH.C=O L-OJ

---t H e b-CHO $ CH2=C=O --+ H KOAc \/ '6 60°C. 0

CH-CH

CeHsCHO + CHa=C=O CaH6CHCHZC=O + KOAC -0.J 60" C.

CsHsCH=CHs + COa

Hurd used anhydrous potassium acetate as a catalyst and in addition to the decarboxylation products he isolated furacrylic acid and cinnamic acid which probably resulted from the depoly- merization of linear polyesters of the corresponding p-lactones upon distillation.

Staudinger in 1911 (16 ) reported diphenylacetylation of the enol of acetophenone with diphenylketene. Vinyl diphenylace- tate was also prepared by the reaction of diphenylketene with acetaldehyde. The enol esters were identified by hydrolysis and isolation of diphenylacetic acid. Gwynn and Degering ( 4 ) in 1942 discovered that enol acetylation with ketene was accom- plished in good yields by using acid esterification catalysts. Ace- tone and ketene reacted in the presence of sulfuric acid catalyst to form isopropenyl acetate.

CHsCOCHa CH-C(OH)CHs + CH2=C=O/EI2SOd + CHFC(CH~)OCOCH~

With the advent of the work of Degering ( 4 ) and Kung (IO) B renewed interest has been taken in the utilization of ketene in the synthesis of organic compounds.

In the author's laboratories the condensation of ketene with itself and with carbonyl *compounds-aldehydes, ketones, dike- tones, keto esters, aromatic aldehydes and ketones, and unsatu- rated aldehydes and ketones-has been investigated. Other catalysts have also been found which are suitable for the conden- sation and in some instances they are superior to the Friedel- Crafts type catalysts for the formation and isolation of p-lactones. Aldehydes and a,p-unsaturated aldehydes and ketones were also enol acetylated.

DIKETENE

The dimerization of ketene should be considered in a study of the condensation of ketene with carbonyl groups. Of the three structures commonly assigned to diketene, p-vinylacetolactone has been chosen as representing the product of the condensation of the carbon-to-carbon double bond of one ketene molecule with the carbonyl group of a second ketene molecule to form a p-lactone.

CHz=C=O + CH,=C=O 50" C. CHz=$Xf;C=O f

No catalyst

L O - 1 LO--] CHaCOCH=C=O CHz=CCH&=O CHaC=CHC=O

I I1 I11

Although many investigators show a preference for either P- vinylacetolactone (11) or 0-crotonolactone (111) as representing

766 I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY Vol. 41, No. 4

the structure of diketene, it is interesting to note that diketene does not form @-alkoxy compounds with alcohols which is char- acteristic of the 0-lactones.

Diketene ( 2 5 ) is manufactured in 90 to 95% yields simply by passing ketene in through a dispersion plate in the bottom of a tower (Figure 1, omit formaldehyde and catalyst feed lines) filled with diketene and overflows continuously at the top of the tower. The rate of addition is controlled so that the liquid overflowing at the top of the tower is substantially free of dissolved ketene. Temperature is the important factor in controlling the dimeriza- tion of ketene and at 40" to 50" C. a smooth rapid rate of dimeriza- tion is obtained. The diketene is fed continuously to a still at reduced pressure, 30 mm., for final purification. Catalysts should never be used in the production of diketene.

Commercially ketene is produced by the pyrolysis of acetic acid at reduced pressure, 40 to 100 mm. Where diketene is the desired product it is prepared by inserting one or more scrubbers in series in the reduced pressure system. Ketene is fed into the scrubber (Figure 2, omit formaldehyde and catalyst feed lines) below the packing support and scrubbed with diketene.

Referring to the diagram, 1 indicates a primary scrubber which may be cooled with water or other cooling agent through the cool- ing coil, 2. The scrubber is packed with Raschig rings and ketene is metered through rotameter, 7, and enters the scrubber through the nozzle, 17, below a packing support. Diketene is circulated by a pump, 16, from the reserve tank, 5, through a cooled line, 13. The rate of flow of diketene through the scrubber is gaged by the rotameter, 15. The off-gas is led out at 22 and passes through a condenser, 9, and a liquid gas separator, 10, to the jet in the re- duced pressure system, Where a high throughput is desired two or more scrubbers are usually connected in series. A copper scrubber 6 feet high and 8 inches in inside diameter packed with 0.5-inch Raschig rings was used to produce 3 to 4 pounds of dike- tene per hour in 97% yield. Diketene is cycled through the scrubber at the rate of approximately 1 to 2 gallons per minute at 30" to 35' C. and is overflowed at 25 to the reduced pressure still.

0-Butyrolactone is produced by the hydrogenation of diLetene with Raney nickel catalyst at 60 to 70' C. and 300 to 500 pounds per square inch in the presence of an equal or larger volume of dil- uent. @-Butyrolactone, benzene, and other inert hydrocarbon solvents are suitable as diluents. In the absence of diluents the hydrogenation cannot be controlled and the diketene decomposes with violence.

CH2=CCH&=0 + Hz diluent CH3CHCH&=0 L-OJ -+ - 0 1

Ni(R) GO" to 70' C.

500 pounds per square inch

On increasing the hydrogenation temperature to 120 O to 160 * C. @-butyrolactone undergoes hydrogenolysis to n-butyric acid.

CH,CHCHzC=O + HZ -- + CH3CHzCHzCOOH L O - _ I Ni(R)

120Oto 150" C.

I n continuous hydrogenation diketene can be hydrogenated di- rectly to butyric acid.

REACTIONS OF KETENE WITH ALDEHYDES A h D KETONES

Ketene and aliphatic aldehydes such as acetaldehyde, propion- aldehyde, and butyraldehyde react in the absence of catalyst to form a,p-unsaturated ketones.

2CHz=C=0 + RCHzCHO RCH&H=CHCOCHj + COz

Actually the ketene dimerizes to diketene and as such reacts with the aldehyde to form a 0-lactone which decarboxylates upon heating to form the a,P-unsaturated methyl ketone (1 ).

CH,COCH=C=O + RCHnCHO + CH3COCH--C=O

then CH,COC€I-C=O + RCHzCH=CHCOCH3 + CO2

RCHz-CH- ' b J17ith acetaldehyde the product is 3-pentene-2-one; with pro-

pionaldehyde 3-hexen-2-one; and with butyraldehyde 3-hepten- 2-one. The reaction is conducted by passing ketene into a solu- tion of the aldehyde a t room temperature. Conversions to unsat- urated ketones average between 50 and 65%,

A similar condensation reaction is not observed with ketones. Ketene and acet,one do react, however, in the absence of a catalyst a t elevated temperatures, to form small amounts of isopropenyl acetate in addition to diketene.

CHz=C=O+CH,COCH,/BO O C. --+ CHz=C(CHJ-OCOCHI

ENOL ACETYLATIONS

With catalysts such as sulfuric acid ( 5 ) , p-toluencsulfonic acid, and particularly with acetylsulfoacetic acid in concentrations of 0.01 to 0.1% and a t 40Oto 80" C., the corresponding enol acetates are formed. Acetylsulfoacetic acid is prepared by the reaction of acetic anhydride with sulfuric acid: the acetic acid is distilled off at reduced pressure (8 ) .

H2S04 + 2( CHsCO) ~O+CHSCO~SO~.~I€~COOH f2CHyCOOH

CHFC=O + CH3CHO/Hd304 + CHFCHOCOCH~ CI€?=C=O + CHaCOCIla/I12304 --+ CH2=C(CH3)0COCHa

In the case of the aldehydes, the a,@-unsaturated kelones \yvliich result froni the condensation of diketene with the aldehydes are formed in increasing amounts as me ascend in the aldehyde series.

TABLE I. ESOL XCXTYLATIOK Unsaturated

$.P. , Conversion, Conversion, Enol Acetate Ketone,

Carbonyl Compound C. % % Acetaldehyde 72 21 Propionaldehyde 99 18 Butyraldehydo 128 7 -4oetone 96 45 RIethyl ethyl ketone 118 31

17 34 51

None None

The conversions are bnsed on the ketene added. Sulfuric acid was used as the catalyst. With acetylsulfoacetic acid as a cnta- lyst, greatly increased conversions to the enol acetates are ob- tained-e.g., with acetone the conversion to isopropenj-1 acetate is 75 t o 8570 as compared with 35 to 45% for sulfuric acid cata- lyst. Anhydrous sodium acetate is also a catalyst for the enol acetylation of acetone with ketene.

p-LACTOhES

In the presence of suitable condensation catalysts, aldehydes and ketones condense with ketene to form @-lactones. Some of the better catalyst materials include boric acid, triacetyl borate, mercuric chloride, zinc chloride, zinc thiocyanate, magnesium pel chlorate, and boron trifluoride etherate.

Catalysts suitable for use In the condensation of ketene with carbonyl compounds generally fall within the classification of a group of salts which are strongly acid in concentrated aqueous solutions ( I d ) . The compounds are capable of forming coordina- tion complexes with hydroxy groups and also have a strong cata- lytic activity towards carbonyl derivatives These compounds in- clude the borates, aluminates, halides, thiocyanates, nitrates, chlorates, and perchlorates of zinc, tin, mercury, aluminum, lith- ium, boron, iron, manganese, and cobalt.

The inactivity of some salts of this group is generally due to their insolubility in the reaction solution.

Although this list includes the Friedel-Crafts type of catalyst, most of the compounds are not Friedel-Crafts catalysts. The cata-

April 1949 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 767

polyoxymethylene acetates due to the prep- ence of water in the 95% paraformaldehyde which is vaporized in the depolymerization and enters the reactor. Under anhydrous con- ditions yields of propionolactone as high as 96% have been obtained.

The reduced pressure reactor (Figure 2) used in the manufacture of diketene was also used in the production of lactones.

The apparatus shown is charged with 50 grams of zinc chloride in 5 gallons of propiono- lactone which is circulated through the scrubber, 1, at 1.5 to 2 gallons per minute. Paraformal- dehyde is depolymerized at 19, metered through a heated rotameter, 8, and mixed with gaseous ketene immediately before entering the scrubber through the nozzle, 17, which is centered below the screen supporting the packing. The reaction temperature is held a t 5' to 10' C. by cooling. There are two factors on which the choice of a reaction temperature depends: (1) to obtain a fast rate of reaction between ketene and formal- dehyde so as to minimize the amount of homo condensations due to the presence of high con- centrations of the monomers in solutions, and (2) to minimize the formation of linear polyesters of the @-lactone.

In a 48-hour run 3.5 grams of ketene per minute and 2.5 grams of formaldehyde per minute were mixed immediately before entering

lyst activity depends on the solubility of the metal salt as well the scrubber. Catalyst make-up was added intermittently as the degree of diwociation in organic media, With aldehydes a t 4 and a concentration of 0.05 to 0.25% was maintained. Pro- and ketones the effective metal salts Can be thought of as forming heater, and then redistilled. A yield of 88% propionolactone, 3% an oxonium'type complex with the carbonyl group. acrylic acid, and 9% residue was obtained.

The choice of a catalyst is important if a high yield of @-lactone is to be obtained. This choice of a catalyst depends on the reac- t i d y of the particular carbonyl compound to be condensed with ketene. For example, with aldehydes (particularly the lower ali-

Conversion Mole phatic aldehydes, formaldehyde and acetaldehyde, and aromatic To di- To Ratio aldehydes) the preferred catalysts are boric acid, triacetyl borate, Ketene, CHIO, ZnCh, T, To lac- ketene acrylio Red- Keten$/

Run Grams Grams % ' C. tone acid acid due CHzO zinc thiocyanate, and zinc chloride. Acetone, methyl ethyl ke- 7 15 1.10/1 tone, methyl pyruvate, and diacetyl require strong condensation 16 3360 2023 3 10 60 4 12 24 1 19/1

12 6 1.03/1 catalysts such as boron trifluoride etherate or acetic acid complex ix :;;i :gig !:: ii !i . 2 14 10 1 05/1 to obtain maximum yields. Zinc chloride acetic acid complex and 20 1990 1422 0.3 10 84 . I 11 5 1 02/1

22 1095 760 . . , 0 3 23 . 71 1.02/1 the metal fluoborates of zinc, iron, and tin can also be included in 23 1440 1031 . , 40 7 21 . 62 0.97/1 this group.

In carrying out the condensation of ketene with aldehydes continuously, it is preferred to add the ketene and aldehyde in equimolar amounts to a solution of the catalyst in the cor- responding lactone. Other solvents such as ethers, alkyl halides, and ketones are also suitable and are preferred in batchwise operation because of the polymerization tendency of the @-lactones.

CONDENSER

PUMP

Figure 1. Condensation Reactor

* pionolactone was taken off continuously a t 25, fed to a flash

TABLE 11. PROPIONOLACTONE

15 3050 2142 3 0 78 3

PROPIONOLACTONE

Ketene and formaldehyde are metered sepa- rately and passed into a solution of zinc chloride in propionolactone. The solution is cycled through the column concurrent with the flow of incom- ing gases and is maintained a t approximately 10' C. by cooling. The lactone is overflowed continuously through a rotameter to a small flash heater at reduced pressure. The crude lactone is then redistilled to remove acrylic acid.

Typical results are reported in Table 11. It was found that some propionolactone is

formed even in the absence of any catalyst. Although the temperature was 40" C. in run 23 and 7% propionolactone was obtained, no acrylic acid was isolated by destructive distilla- tion of the residue. The residue formed in the presence of catalysts is comprised largely of Figure 2. Reduced Pressure Reactor for Ketene Reactions

768 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 41, No. 4

Table 111. Products from Aliphatic Aldehydes and Ketones Carbonyl Compound Lactone Reduction Polymerization and Pyrolysis Alcoholysis (9) Decarboxylation Formaldehyde Propionolactone Propionic acid Acrylic acid 8-Alkoxypvopionic acid Ethylene Acetaldehyde P-Butyrolactone Butyric acid Crotonic acid P-Alkoxybutyric acid Propylene Acetone 0-Methyl-8-butyrolactone Isovaleric acid P,8-Dimethylacrylic acid 8-Alkoxyisovaleric acid Isobutylene Methyl ethyl ketone 8-Ethyl-B-butyrolactone 3-Methylpen- 8-Methyl-p-ethylacrylic acid 2-Alkoxv-2-methvl uentanoic 2-Methvl-1-butene _ .

tanoic acid acid Butyraldehyde 8-Propylpropionolactone Caproic acid 8-Propylacrylic acid P-Alkoxycaproic acid I-Pentene

Propionolactone can be purified by redistillation at 28" C. and 3 mm. to give a product showing no unsaturation on the infrared spectrometer. The pure lactone has the constants: n"," 1,4135, dEo 1.1489, melting point -31.2" C., boiling point 51" C. at 10 mm.

Acetaldehyde and ketene reacted similarly, using a solution of 0.25% zinc chloride in p-butyrolactone. An 85% yield of P-buty- rolactone r a s obtained. Diketene and methyl propenyl ketone are by-products.

With ketones such as acetone and methyl ethyl ketone the re- action is carried out in the presence of excess ketone, which is recovered and recycled.

CHaCOCHa + C H e C = O --+ CHs-C(CH8)-0 0°C. I

BF3 etherate CH2----&=0

b.p. 54" C. at 10 rnm.

a n d

CHsCHzCOCHs + CHz=C=O + CHaCHzC(CHa)-0 AHz---C=O I

b.p. 60" to 61 O C. at 10 min.

As the molecular weight increases the problem of isolating the lactone becomes more difficult because of a tendency to decar- boxylation. However, once the p-lactones are isolated in the pure state, they are stable compounds a t rooin temperature.

If an unsaturated acid is desired as the final product, the reac- tion between ketene and the carbonyl compound is carried out a t 40 O to G O o C. to give a low molecular weight linear polyester of the @-lactone directly. This linear polyester is then depolymerized by distillation to form the a,p-unsaturated acid ( b , l f ).

CHa=C=O + CHZO/ZnCl2 40" to 60" C. -OCHzCH2CO- + [OCHZCI~ZCO] -OCH&IIzCO

-CO [OCH~CH~CO],O/CU(OAC)~ A CHz-CHCOOH --+

I n this particular case a small amount of copper acetate is added as an inhibitor to vinyl polymerization prior to the distillation. Some of the products which are obtained from aliphatic aldehydes and ketones with ketene via the p-lactones are listed in Table 111.

Furfural gave only tars and uncontrollable reactions with zinc chloride and similar catalysts. Furacrylic acid and cinnamic acid were prepared by the reaction of ketene with furfural and benxal- dehyde, respectively, a t G O o C. using sodium acetate catalyst fol- lowed by destructive distillation. Yields were 40 to 60%.

UNSATURATED ALDEHYDES AND KETONES

Unsaturated aldehydes and ketones can react with lret m e to give a variety of products. In the presence of suitable conden- sation catalysts ketene adds both 1,2 and 1,4 to form p(1)- and a( 11)-lactones.

RCH=CR-CR=O + CHt=C=O/ZnCl2 0 to 10 O 0. 4 3 2 1

+ RCH=CR-CR-CHz $. RCHCRcCRO

I c=o 1 1 I O--C=O CH2

I I1

R can be hydrogen, alkyl, or aryl. The &lactones are decarboxylated by pyrolyzing 0.r heating at

temperatures above 100" to 120" C. to form diene derivatives. &Lactones decarboxylate a t slightly higher temperatures and also form diene derivatives.

I

RCH=CR-CR-CH2 A RCH=CR--CR=CH2 + Cod 1 --f

0 - L o RCHCR=CRO

A CHz=CR--CR=CHR + COz + I I CHz-----C=O

P-Lactones are usually formed in the ratio of 10 to 1 of the delta lactones as calculated from the yield of olefinic decomposition products obtained from the condensation of crotonaldehyde with ketene (Table IV). If a doubly unsaturated acid is the desired product, the condensation is carried out a t 40' t o 50" C. and a product is obtained comprising largely the linear polyesters of the lactones. Destructive distillation a t reduced pressure result5 in the formation of the doubly unsaturated acid. Sorbic acid is manufactured in 70 to 80% yields in this may from crotonaldchyde and ketene.

With enol esterification catalysts, and a t 50" to 80" C., the wr- responding acetoxy dienes are formed. For example, 1-ace1 oxy-

AROMATIC ALDEHYDES AND KETONES

Benzaldehyde and acetophenone reacted with ketene; boric acid and zinc chloride were used as catalysts at, 0 O to 10' C. De- carboxylation gave good yields of styrene and a-methylstyrene, respectively.

CsI15CHO + CH-C=O --+ CeHsCHCHzC=O L-0-J

Acetone was uaed as diluent in the benzaldehyde reactioii. The yield of styrene was approximately three times as much with boric acid catalyst as with sodium acetate. The aromatic ketones gave no reaction with sodium acetate catalyst.

CsH&HCHzC=O A CBH~CH=CHZ KaOA4c 12%, &BO3 34% ' - 0 2 +

TABLE IT'. U S S A T U R A T E D -4LDEHYDES AND l<ETOKES

Condensation Condition--

Carbonyl followed by followed by de- Enol Acetylation 0" to 10' C . 50' to 60" C .

Compound decarboxylation polymerization Conditions Crotonaldehyde 387, Piperylene Sorbic acid l-Acetoxy-1,3-

6 0 - 6 1 O C. Methacrolein Isoprene 4-hIetiiyl-2,4- No reaction

Ethacrolein Z-F,thyi-l&buta- 4-Ethyl-2,4- 1-Acetoxy-2-methyl-

Methyl vinyl Isoprene 2-Acetoxy-l,3-buta- ketone diene, b.p.io 54' C.

Methyl isopro- 2,3-Dimethyl-1,3- ''-Ace toxy-3-me thyl- penyl ketene butadiene l,a-butadiene,

4% Isoprene butadicne, b.p.40

pentadienoic acid

acid b.p.40 67' c. diene pentadienoic 1,3-bntadiene,

1,2-Dimethyl-1,3- b.p.ro 62' C. butadiene

April 1949 169

1,a-butadiene is produced by the reaction of ketene with crotonal- dehyde in the presence of sulfuric acid a t 60 O t o 80 O C.

I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

60-80 O C. CHZ=C=O + CHaCH=CHCHO/HzS04

CH2=CHCH=CHOCOCHs

Some of the products which have been formed with the com- mon ~ l , p unsaturated aldehydes and ketones are reported in Table IV.

All these products are useful in resins, drying oils, etc. The enol acetates form both rubbers and resins and can be polymer- ized and copolymerized.

DIKETONES

Ketene condenses with diketenes to form the mono- and di-p- lactones. I n the absence of excess ketene the decarboxylation products indicate the formation of both the mono- and di-&lac- tones.

For example, 86 grams of diaoetyl were diluted with 250 ml. of ethyl ether containing 12 ml. of boron trifluoride etherate and 2

ram moles of ketene were passed in through a high speed stirrer. !!he catalyst was neutralized with anhydrous sodium acetate and the mixture was distilled a t atmpspheric pressure. Four grams of 2,3-dirnethyl-lJ3-butadiene, bo.il?ng point 68 O Cb! and 12 grams of methyl isopropenyl ketone, boihng point 95-98 C. were isolated in addition to 47 grams of unchanged diacetyl.

o o c. CH3COCOCI33 + 2 CHz=C=O BFetherate-) '

@-lactone increases, and higher yields of the unsaturated esters are obtained. Hydroxydicarboxylic acids can be formed by hydroly- sis of the crude lactone, and with alcohols the corresponding al- koxydicarboxylic acid diester is produced. HYDROLYSIS

CH&(CHg) --CHzCOOCzHs + + NaOH, HC1 O = L B HOOCCHzC(CHs)-CH&OOH + CzH5OH

AH ALCOHOLYSIS

CZH~OOCCH~C (CHI) -CHzCOOC2Hs

dCaHs

Enol acetylation of methyl pyruvate gave a low yield of methyl a-acetoxyacrylate. Ethyl acetoacetate and ethyl levulinate led to a mixture of isomers-e.g., with acetoacetic ester.

CH&OCHzCOOC~Hs + CHz=C=O/HzSO4 60-80 A C

0 0

CHz==C--CHz b OCz& + CHsC=CH E OCzHs

CHzC(CH3) COCHs CHzC(CHs) C(CHJ CHo bCOCH8 bCOCH3

o= -0 A-d-o The enol acetates of acetoacetic ester rearrange on prolonged heating in the presence of acid catalysts to form ethyl diacetylacetate. This compound boils slightly below the mixture of enol acetate isomers and has a higher index of refraction n2: = 1.4690

6=L-0 + A ' A CH&(CHJCOCHs -+ CH~=C(CH~)COCHI + COz

o= A ' -0

CHpC(CHs)~(CHa)~& - * + CHz=C(CHdC(CHs)=CH2 4- 2 0 2 as compared to 1.4420 for the enol acetate isomers. I I

o=LO a--(5=0 Degering (16) and Hurd ( 7 ) both reported the acetylation of the

enol forms of diketones with ketene in 1944. It is interesting to note that whereas the mono and dienol acetates of diacetyl and acetylacetone can be prepared, acetonylacetone is only cyclized under acetylation conditions and no enol acetates have been iso- lated. Under condensation conditions the decarboxylation prod- ucts of both the mono- and di-@-lactones from acetonyl acetone and ketene were isolated. The products of the reaction of ketene with diketones under both condensation and enol acetylation conditions are summarized in Table V.

KETO ESTERS

Methyl pyruvate, ethyl acetoacetate, and methyl levulinate also reacted with ketene under condensation and enol acetylation conditions. No effort was made to isolate the 8-lactones but the decarboxylation products were isolated instead. Methyl pyru- vate reacts with ketene to form a &lactone, which is then decar- boxylated to form methyl methacrylate.

0 ° C CHsCOCOOCHa + CHa==C=O/BF3 etherate __.f

CHa C(CHa)COOCH~

o=c- ' b CHz--C(CHs)-COOCH3 + CH2=C(CHs)-COOCH3

I / O=%-d

The enol acetates of the ketoesters can be copoly- merized with polymerizable vinyl monomers in the

presence of peroxide catalysts to give clear, colorless resins. Some of the compounds which can be prepared from keto esters and ketene are reported in Table VI.

'

,

TABLE V. REACTION PRODUCTS OF KETENE WITH DIKETONES Carbonyl Condensation Conditions

Compound Decarboxylation Product; Enol Acetylation Produots Diaoetyl

Aoetylacetone

Acetonylaoetone

14% methyl isopropenyl ketone

5% 2 3-dimeth~l-l.3-buta- dieie, b.p.rss 68' C.

27% 4-methyl-4-penten-2- one b.p.785 127' C.

14% '2,4-dirnethyl-l 4-pen- tadiene, b.pm 8 8 O ' C:

2,5-Dimethyl-l,5-hexa&ene, 5-Methyl-5-hexene-Z-one, b.p.?84 112' c.

b.p.784 154' c.

4% or-acetoxyvinyl methyl 1.7% ketone, 2 3-diacotoxy-1 b.p.5 3 Z e C. 3-

butahiene, b.p.6 53& C. 43% I-methyl 2-acetylvinyl '

acetate, b.p.10 84O C. 18% 2,4-diacetoxyplperyl-

ene, b.p.la 114' C. 85% 2,5-dimethylfuran

TABLE VI. PRODUCTS OF KETO ESTERS AND KETENE Carbonyl Condensation Conditiono,

Compound Deoarboxylation Products Enol Acetylation Product

pyruvate b.p.io 62" C. Methyl 14% methyl methacrylate Methyl a-acetoxyacrylate,

Ethyl 84% ethyl isopropenyl- 70% ethyl 3-acetoxycrotonate acetoacetate acetate, b.p.eo 54.5' C., and isomer, b.p.to 94O C.,

nv 1.4400, d$' 1.0159 nZ,O 1.4420, dgg 1.0659

Methyl, levulinate

Ethyl levulinate

Methyl 8-isopropenylaro- pionate; b.p.zo 54' C., ny 1.4224, d g 0.9346

Ethyl diacetylacetate, b.p.10 89' C.. ny 1.4690

38% ethyl 4-aoetoxy-4-pen- tenoate and isomer, b.p.6 8Q0 C.,n2,O 1.4361, diz 1.0478

Ethyl acetoacetate and methyl levulinate undergo the same condensation to form unsaturated esters. As the carbonyl group is removed from the carboxyl group the ease of formation of the

770 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 41, No. 4

REACTIOR O F KETERE WITH HYDROCYANIC ACID (8, 18)

The reaction of ketene with hydrocyanic acid shows the forma- tion of an enolizable kctonitrile (IC) which is subsequently acety- lated to form the enol acetate. The reactions which occur are represented by the equations

CH*=C=O + HCN + CH3COCN + CII2=C(OH)CN

then

CHZ=C(OH)CK f CH2=C=O CHz==C(OCOCH,)CS

In addition to a-acetoxyacrylonitrile a small amount of the dimer of pyruvonitrile is also formed

2CHaCOCN -+ C H J C O ~ C ( C N ) ~ C H ~ a-acetoxyisosuccinic dinitrile

The dimer can be pyrolyzed a t elevated temperatures or dis- tilled in the presence of basic catalysts such as sodium acetate to

The reaction of ketene with hydrocyanic acid is carried out by passing ketene into hydrocyanic acid in the presence or absence of diluents, a t -10" to + loo C. Diluents are used mainly to reduce the vapor pressure of the hydrocyanic acid and a-acetoxyacrylo- nitrile itself is a preferred diluent for the reaction. Although con- siderable reaction is obtained in the absence of catalyst, the high- est yields are obtained with a mildly basic catalyst. Anhydrous sodium and potassium acetate are superior to the alkali cyanides and tertiary nitrogenous compounds as catalysts.

I n this reaction an optimum concentration of catalyst has been observed. With no catalyst or too low a concentration of cata- l j r s t , diketene is formed in large amounts. With too high a con- centration of catalyst the dimerization of pyruvonitrile increases and considerable amounts of a-acetoxyisosuccinic dinitrile are formed.

A comparison of average results with and without sodiuni ace- tate catalyst is reported in Table VII. These runs were carried out operating continuously using the column shown for dilcetene and propionolactone (Figure 1). Unreacled hydrocyanic acid was separated from the product by distillation and recycled to the reactor, The residue was mainly a-acetoxyisosuccinic dinitrile.

* yield a-acetoxyacrylonitrile and hydrocyanic acid.

TABLE I'II. REACTION OF T C s m m VI'ITII HYDROCYANIC A C I D

Acetoxy- acrylo- nitrile

Ketene Ketene Resin Yield on to di- Yield, % of' Ketene,

Conversion, yo

IICN Ketene ketene c70 Total Average % S o catalyst 24 40 44 78 6 . 5 12 runs 34

74 18.0 12 runs 60 0.0870 XaOAc 42.5 70 14 0.34 , KaOAc 70 88 0 . 1 88 8 . 7 7 rnns 88 0.457, NaOAc 58 67 2 . 5 66 30 12 rnns 6 3 . 5

a-,~cetoxyisosuccinic dinitrile can be formed alniost t o the ex- clusion of a-acetoxyacrylonitrile by carrying out the reaction with hydrocyanic acid as a 50% solution in acetic acid a t 0" C. and with 0.370 sodium acetate catalyst. Less than 10% acetic anhydride is formed as a by-product.

LITERATURE CITED

Boese, A. B., U. S. Patent 2,108,427 (Feh. 15, 1938). Ibid., 2,382,464 (Aug. 14, 1945). Dommoni, T. F., and Cuneo, J. F., Zbid., 2,411,823 (Nov. 26,

Gwynn, B. H., and begering, E. F., J . Am. Chem. SOC., 64, 2216

Gwynn and Degering, U. S. Patent 2,383,966 (1942). Hurd, C. D., J. Am. Chem. SOC., 55, 275 (1933). Hurd, C. D., Edwards, E. E., and Roach, J. I<., Ibid., 66, 2013

Johnston, F., and Newton, L. W., U. S. Patent 2,395,930 (March

Kung, F. E.,Ibid. , 2,352,641 (JuEy4, 1944). Ibid., 2,356,459 (Aug. 22, 1944). Ibid., 2,361,036 (Oct. 24, 1944). hfeerwein, Ann., 455, 227 (1927). Mugdan, M., and Sixt, J., U. S. Patent 2,216,450 (Oct. 1, 1940). Roy, G. C., Ibid., 2,396,201 (March 5, 1946). Spence, d. A., and Degering, E. F., J . Am. Chem. Sac., 66, 1624

Staudinger, Ann., 384, 51 (1911). Staudinger and Kon, Ibid., 384, 38-135 (1911). Trollman, Schlaffer, and Ostrowski, German Patent 736,504

1946).

(1942).

(1944).

6, 1946).

(1944).

(1943).

RECEIVED March 8, 1948. Presented in the Symposium on Industrial Processes, American Bssociation for the Adranoemont of Science, Chicago, Ill., December 2 6 , 1947.

Relations for J. W. WILSON AND GEROULD H. SMITH Union Oil Company of California, Oleum, Calif.

MARKED advance in the measurenient of the viscous prop- A erties of lubricating greases was disclosed by Arveson (1) in papers published in 1932 and 1934. His results were obtained on a novel apparatus employing constant flow rate rather than constant pressure. Beerbower, Sproule, Patherg, and Zimmer (2 ) have developed a simplified apparatus of lhis type in n-hich constant f l o ~ rate is obtained by means of hydraulic oil and an accurate metering pump. This apparatus, which is known as the S.O.D. pressure viscometer (Precision Scientific Company, Chi- cago, Ill.) has led to a large amount of work on the flow char- acteristics of lubricating greases (e, .$, 8, 9, 11, 13).

Arwson used his data to calculate consistency values, which he termed "apparent viscosity," v a , by means of the Poiseuille equation :

As lubricating greases are non-Kewtonian in character, differ- ent values of qa will be obtained for a grease a t diffcrcnt rates of f l o ~ in a given capillary, or a t a given rate of flow in capillarics with different radii. Arveson showed that by plotting qa against the expression 4Q/n-IP, most suitably on logarithmic scales, smooth curves could be obtained. This expression, 4Q/n-R3, Cali

he shown mathematically to be the rate of shear, S, a t the wall of a capillary for the flow of a Nevtonian fluid. For a lion-Sew- tonian fluid, the cxprcssion only approsirnates the rate of shear at, the wall; nevertheless, there are abundant data obtained with the S.O.D. viscometer t'o indicate that if the dimensions of two