DE1121605B - Process for the preparation of enol acetates - Google Patents

Description

Ketene can be known to be either under with carbonyl compounds in the presence of catalysts Formation of / 3-lactones or enol acetates react. If acetone is used as the carbonyl compound, / S-methyl-ß-butyrolactone (I) or isopropenyl acetate can be used (II) arise:

H ₂ C = C = O + H ₃ C-CO-CH ₃ >

catalyst

, HC

C = O

H, C,

H ₃ C

C O

or

catalyst
H ₃ C-CO-CH ₃ H ₃ CC = CH ₂

OH

+ H ₂ C = C = 0

Hq C-C-CHe

OCOCH,

II

Lactone formation is caused by heavy metal salts (zinc, cobalt, iron (II), lead, Cadmium) catalyzes the difluorophosphoric acid.

It has now surprisingly been found that enol acetates by the reaction of ketene with enolizable carbonyl compounds, a phosphoric acid catalyst can be conveniently prepared at temperatures between 20 and 110 ° C, preferably at 60 to 8O ⁰ C, in the presence when the catalyst difluorophosphoric acid or a mixture from equimolecular amounts of difluorophosphoric acid and monofluorophosphoric acid or the reaction product, that of 1 mole of phosphorus pentoxide and 3 moles of hydrogen fluoride according to the equation

HPO ₂ F ₂ + H ₂ PO ₃ F

arises, is used.

The process can be carried out either batchwise or continuously, with as a result the higher reaction temperatures inevitably required in continuous operation and the The associated increase in the reaction rate kept the catalyst concentration lower can be compared to discontinuous operation.

The formation of enol acetate from an enolizable carbonyl compound and ketene is an identical process for the production of enol acetates

Applicant:

Wacker-Chemie GmbH,
Munich 22, Prinzregentenstr. 20th

Dr. Theodor Altenschöpfer, Dr. Eduard Enk,
Dr. Fritz Knörr and Dr. Hellmuth Spes,

Burghausen (Obb.),
have been named as inventors

weight reaction. Are very reactive carbonyl compounds before, such as B. ethyl acetoacetate, so suffice to achieve the enolization a relatively small amount of catalyst and a relatively small excess of carbonyl compound.

In the case of relatively unreactive carbonyl compounds, for example acetone, special measures must be taken to ensure that that the very reactive ketene molecule as many carbonyl molecules as possible in the reactive enol form finds. This can be done by presenting a large excess of carbonyl compound can be accomplished with the keten. Weak catalysts (e.g. phosphoric acid, p-toluenesulfonic acid, m-nitrobenzenesulfonic acid) a larger excess of carbonyl compound than strong catalysts, such as. B. acetylsulfoacetic acid or the reaction product of naphthalene-1,5-disulfonic acid + acetic anhydride.

The ketene-carbonyl compound molar ratio varies within relatively wide limits depending on the constitution of the carbonyl compound. With easy enolizable carbonyl compounds, such as ethyl acetoacetate, a molar ratio of 1: 1 is sufficient.

In the case of carbonyl compounds that are difficult to enolize, for example acetone, a complete Ketene absorption or, to prevent undesired side reactions, a molar ratio of ketene to carbonyl compound of at least 1.4 moles of carbonyl compound per mole of ketene in continuous operation and a molar ratio of at least 1: 1.2 can be used for discontinuous operation.

109 759/420

3 4

For economic reasons one keeps the overreaction of the same with ketene. This is special

carbonyl compound as low as possible, in that it is advantageous, since in reuse, back-

by using a relatively high catalyst-obtained carbonyl compound still containing enol acetate

Concentrations of the percentage of enolized bonds, darker stains can occur Carbonyl molecules is increased. 5 make the dosage difficult.

An increase in the catalyst concentration are

but relatively narrow limits, because not only example 1
an enolization of the carbonyl compound takes place,

but also an overenough can occur, In a boiling mixture of 406 g (7.0 mol)

whereby with elimination of water unsaturated io acetone and 10 g (0.098 mol) difluorophosphoric acid,

Hydrocarbons or their polymerization processes which are in a glass frit flask equipped

forming products. The separated water reacts with a thermometer and reflux condenser, is located

2 moles of ketene with the formation of undesirable vinegar become a total of 220 g within 3.66 hours

acid anhydride. Therefore, a catalyst (5.24 mol) ketene has a rate of 60 g

concentration of 0.01 to 2 ° / ₀ , based on the 15 (1.43 mol) ketene fed per hour, accordingly

Sum of the reactants, ketene-acetone fed advantageously in a molar ratio

proven. = 1: 1.34. The catalyst concentration is

The catalyst concentration is also from 4.54%, based on the fed ketene, or 1.57%, depending on the residence time of the carbonyl ketene, based on the sum of the reactants, mixture in the reaction vessel. A reduction of 220 g (5.24 mol) of ketene, that is 100% of the ketene passed through to the catalyst amount, is absorbed,
It can be achieved that the ketene molecules as possible The vaporized acetone is condensed by freezing a long reaction path in the liquid carbonyl and is presented to the reaction bond via a siphon. But vessels are also redirected here. After neutralization and limits set, since if a critical final distillation is exceeded, the reaction equilibrium is disturbed from 636 g of crude residence time

and a regression of the end product to the starting 121.2 g (2.10 mol) acetone,
common substances takes place. It should be noted that 425.2 g (4.25 mol) of isopropenyl acetate,
the critical residence time at a given molar ratio 4.02 g (0.06 mol) acetic acid,
Ketene carbonyl compound depends on the size 30 44.8 g (0.44 mol) acetic anhydride,
the approach and thus inevitably the amount of catalyst. The acetic anhydride can be replaced by a second

In order to purify the pure enol acetate quantitatively from the distillation, so that that of the vinegar reaction mixture to isolate, e.g. B. by distillation, acid anhydride corresponding ketene value (36.9 g it is advantageous to neutralize the catalyst. 35 = 0.88 mol) in the yield calculation as back-die Neutralization can be achieved in the continuous recovery of ketene »in the form of acetic anhydride« drive continuously, while it can be taken into account in the case of discounting. Based on these numbers natural procedure is carried out in batches. there is a 60.6% conversion of the pre-this In the discontinuous process, it is acetone placed in isopropenyl acetate. The highly recommended that the neutralization is as immediate as possible conversion of the ketene to isopropenyl acetate takes place after formation of the reaction product. 81.2%, based on the supplied ketene. Yield to

In contrast to most of the isopropenyl acetate known to date: 86.5%> based on consumed

Catalysts can use difluorophosphoric acid as acetone, and 97.4% based on consumed

Catalyst not only for discontinuous ketene.

but also during continuous operation without 45 When working under completely identical conditions,

further a practically complete absorption of the but using polyphosphoric acid as

supplied ketens can be achieved. Special pre-catalyst is obtained from 406 g (7.0 mol) of acetone,

directions, such as circulation evaporator or quickly 220 g (5.24 mol) of ketene and 10 g of polyphosphoric acid

running stirrer for better mixing of the quantitative ketene absorption

supplied ketene with the carbonyl compound, 50,152 1 g (2,62 mol) acetone

can be used The application 361J5 g & 61 mol) isopropyl acetate,

Such mampulations, however, result in a substantial amount of _{(0Q31 mol) acetic acid}

loan advantages since the encryption Enolacetatbildung under _{49 4} J _{(0 48 mole) Essigsäureanh} y _drid.
use of difluorophosphoric acid as a catalyst

done extremely easily. It can therefore be increased to 55. This results in a 51.6% conversion of the

promoting mechanical measures completely submitted acetone in isopropenyl acetate. The Um-

be waived. Conversion of the ketene in isopropenyl acetate is

In terms of technical recovery, this is 69.0% based on the ketene fed in. Yield of availability of particular advantage, since no mobile isopropenyl acetate: 82.5%, based on the parts consumed, such as stirrers or pumps, are used, 60 acetone, and 84.5%, based on the ketene consumed. must, which of the acetic anhydride formed in small amounts as a by-product, which example 2
a rather aggressive substance, attacked

can be. In one with a thermometer and a reflux cooler

The addition of the catalyst to the carbonyl-equipped reaction vessel becomes a mixture of

Binding takes place as a result of the easy miscibility of the 284.2 g (2.84 mol) of isopropenyl acetate and 284.2 g

Difluorophosphoric acid with carbonyl compounds (4.90 mol) acetone and 5.7 g (0.056 mol) difluoro

heated to the boil by means of a metering pump immediately before the phosphoric acid, and every hour

to 214.5 g (3.69 mol) of acetone, 142.5 g (3.40 mol) of ketene and 3.50 g (0.034 mol) difluorophosphoric acid, corresponding to an amount of 2.45 ° / ₀ of ketene fed. After the ketene feed has started, the supply of heat is dispensed with, since the isopropenyl acetate formation, which takes place in an exothermic reaction, releases enough heat to maintain the required reaction temperature. After the acetone has been separated off by freezing, the exhaust gas is passed through an absorption tower sprinkled with acetic acid, in which any ketene still present reacts with the acetic acid to form acetic anhydride. The reaction product formed is drawn off continuously via a cooler. The molar ratio of ketene feed to acetone fed in is 1: 1.09, corresponding to a molar ratio of absorbed ketene feed to acetate = 1: 1.11; this corresponds to a molar ratio of supplied ketene to total acetone = 1: 1.45 or a molar ratio of absorbed ketene to total acetone = 1: 1.47. The Ketenabsorption in the reactor is 561.3 g (13.39 moles), corresponding to an absorption of 98.3 ° / ₀ of the supplied ketene. The residence time of the reaction product in the reactor, which is defined as the quotient of

Grams of reactor content

Grams of production per hour '

is 1.60 hours. After a reaction time of 4 hours, within which 570.8 g (13.60 mol) of ketene, 858, Og (14.76 mol) of acetone and 13.98 g (0.137 mol) of difluorophosphoric acid are obtained from 2007.4 g of reaction product by neutralization with sodium acetate and subsequent distillation

410.2 g (7.05 moles)
1411.9 g (14.09 moles)

2.2 g (0.037 mol)

99.9 g (0.98 mol)

Acetone,

Isopropenyl acetate, of which newly formed in reaction: 1127.7 g (11.27 mol),

Acetic acid (after subtracting the neutralization of the difluorophosphoric acid with Sodium acetate formed acetic acid), acetic anhydride.

35

40

45

Based on these figures, the following balance results: conversion of the run up in acetone isopropenyl 76.3 ° / _0th Conversion of the supplied ketene into isopropenyl acetate 82.8% or 84.3% conversion of the absorbed ketene into isopropenyl acetate. The isopropenyl acetate yield is 89.4% based on acetone consumed and 99.1% based on ketene consumed.

When working under completely identical conditions, but using polyphosphoric acid as a catalyst, only 1890.1 g of reaction product are obtained. The Ketenabsorption is 444.0 g (10,54MoI) which are 77.6 ° / ₀ of the supplied ketene. As a result of this incomplete ketene absorption, the molar ratio of absorbed ketene to feed acetone is 1: 1.4; this corresponds to a molar ratio of absorbed ketene to total acetone = 1: 1.86. Compared to the use of difluorophosphoric acid as a catalyst, the residence time of the reaction product in the reactor increases from 1.60 hours to 1.75 hours. After the reaction has ended, 1890.1 g of reaction product are obtained by distillation

676.0 g (11.62MoI) acetone, 919.8 g (9.19 mol) isopropenyl acetate, of which newly formed in reaction: 635.6 g (635 mol), 15.6 g (0.26 moles) acetic acid, 133.8 g (1.31 moles) acetic anhydride.

The run up of acetone in isopropenyl acetate conversion 43.0% on the basis of these figures results using polyphosphoric acid in a concentration of 0.98 ° / _0, based on the sum of the reactants, the following balance. Conversion of the supplied ketene into isopropenyl acetate 46.7% or 60.2% conversion of the absorbed ketene into isopropenyl acetate. The yield of isopropenyl acetate is 79.0 g, based on consumed acetone, and 80.4 ° / ₀ based on consumed ketene.

Example 3

In a manner analogous to Example 2, a starting mixture of 300.5 g (3.0 mol) of isopropenyl acetate, 300.5 g (5.17 mol) of acetone and 6 g of an equimolecular mixture is poured ^{into a reaction vessel with a capacity of 700 cm 3} monofluorophosphoric acid and difluorophosphoric acid for 5 hours, a total of 817.4 g (19.46 mol) of ketene, 2706g (46.60 moles) of acetone and 34.5 g of an equimolecular mixture of monofluorophosphoric acid and difluorophosphoric acid, corresponding to an amount of 4.22 ° / ₀ of the ketene, fed at a rate of 163.5 g (3.90 mol) of ketene, 541.2 g (9.34 mol) of acetone and 6.9 g of an equimolecular mixture of monofluorophosphoric acid and difluorophosphoric acid per hour. This corresponds to a molar ratio of fed ketene to total acetone = 1: 2.66. The resulting molar ratio of absorbed ketene to total acetone is 1: 2.74. The ketene absorption is 807.2 g, that is 98.8% of the ketene fed in. The residence time is 0.86 hours. The catalyst concentration is 0.98 ° / _0, based on the sum of the reactants. After the reaction has ended, 4140 g of reaction product are obtained by neutralization with sodium acetate and subsequent distillation:

1969.3 g (33.9 mol) acetone,

1762.4 g (17.62 mol) of isopropenyl acetate, of which in

Reaction newly formed: 1461.9 g (14.61 mol)

25.4 g (0.42 mol) acetic acid (from neutralization),
226.0 g (2.22 moles) acetic anhydride.

Based on these figures, the following balance emerges: Conversion of the acetone introduced into isopropenyl acetate 31.4%. Conversion of the forwarded Ketene in isopropenyl acetate 75.1% and 76.1% conversion of the absorbed ketene to isopropenyl acetate, respectively. The yield of isopropenyl acetate is 81.7%, based on acetone consumed, and 99.0%, based on ketene consumed.

Example 4

In a manner analogous to Example 2, in a reactor with a capacity of 100 liters Starting mixture of 42 kg (420 mol) isopropenyl acetate,

7 8

18 kg (310MoI) acetone, 3 kg (29.4 mol) acetic acid neutralization, a total of 83.5 kg (1.02 kg mol) sodium anhydride and 0.279 kg (2.74 mol) of difluorophosphorus acetate were consumed, obtained by distillation: acid for 6 hours total 31.86 kg (757.9 mol)

Ketene, 72.7 kg (1252 moles) acetone and 0.23 kg 10 199 kg (175.9 kg moles) acetone,

(2.26 mol) difluorophosphoric acid, corresponding to a 5 22340 kg (223.4 kg mol) isopropenyl acetate,

Amount of 0.72% of the ketene, with a speed of 124.6 kg (2.18 kg mol) of acetic acid, of which in re-

ability of 5.31kg (126.3 mol) ketene, 12.117 kg action formed: 81.5 kg (1.36 kg mol),

(208.6 mol) acetone and 0.038 kg (0.376 mol) difluoro _{9? G 4 k (9 59 k mol) acetic acid anhydride}

phosphoric acid fed in per hour This corresponds _{to the} distillation residue

Total ketene 10 _{WQnnen fed to a molar ratio} . _{125 k (J 23 k mol)}

acetone = 1: 2.06. The ketene absorption is quantitative. ,. ". _{,, C} " ,. ° '..

The residence time is 5 hours. The catalyst ³³⁴ ' ^{6 k} 8 (°' ⁹ f / o ^de , ^{r Em} l ^a g ^e ) _u ^D f ^stll l ^atl ° ⁿ /:,

concentration is 0.31%, based on the sum of the dry residue containing 114.2 kg

Respondents. After the reaction has ended, a salt mixture of Natnum-Di-

from 167.069 kg of reaction product, that is 99.4% of the 15 fluorophosphate and sodium acetate,

material used, through neutralization with 242 kg (0.71% of the filler) distillation

0.590 kg (7.2 mol) of sodium acetate and subsequent lust.
Obtain distillation:

Based on these figures, the following balance emerges:

50.469 kg (870.1 mol) of acetone, ₂₀ conversion of the acetone introduced into iso-

105.11 kg (1050MoI) isopropenyl acetate, propenyl acetate thereof 56.4 ° / _0th Conversion of the forwarded

newly formed in reaction: 63.11 kg of ketene in isopropenyl acetate 89.5% or 89.9%

(631.1 mol), conversion of the absorbed ketene to isopropenyl

0.374 kg (6.25 mol) of acetic acid, of which in acetate. The yield of isopropenyl acetate is

action formed: 76.2 g (1.27MoI), ^a 5 96.1%, based on acetone consumed, and 98.1%,

8.328 kg (81.57 mol) of acetic anhydride, of which 8 ^{relate to} consumed ketene.

newly formed in reaction: 5.328 kg

(52.3 moles), Example 6

0.732 kg of higher-boiling components, _{3O in a mixture of 687 g (70 mol) of} cyclohexanone

1.296 kg of organic residue, corresponding to _un d ^ 4 _{g of} difluorophosphoric acid, which is in one

0.78% of the deposit. Glass frit flasks equipped with thermometer and

Rückfiußkühler located, are at a reaction on the basis of these results the following figures balance Temperature 72-76 ⁰ C within ₂ hours 3V conversion of the run up in acetone iso-35 210 g (5.0 mol) of ketene with a Geschwinpropenylacetat 50.4% · Conversion of the fed rate of 60 g (1.43 mol) of ketene per hour to ketene in isopropenyl acetate 83.4%. The yield passed on. This corresponds to a molar ratio to isopropenyl acetate is 91.3%, based on transferred ketene-cyclohexanone = 1: 1.4. The catalyst consumed acetone and 96.8%, based on the analyzer concentration, is 0.16%, based on the required ketene. 40 Total of respondents. The reaction mixture 5 is obtained by vacuum distillation, 567 g

(4.05 mol) cyclohexenyl acetate from boiling point 99 to

In a manner analogous to that in Examples 2 and 3 100 ^c C at 50 mm mercury column, corresponding to a

are in a reaction vessel of 1080 1 capacity conversion of the ketene in cyclohexenyl acetate of

capacity in a starting mixture of 712 kg (12.3 kg mol) 45 81%.

Acetone and 2.14 kg (0.021 kg mole) difluorophosphorus - Example 7
acid for 164 hours a total of 10 496 kg

(250 kg mol) ketene, 23 028 kg (397 kg mol) acetone In a mixture of 614.0 g (8.5 mol) n-butyr

and 71.77 kg (0.704 kg mole) of difluorophosphoric acid, aldehyde and 1.2 g of difluorophosphoric acid, which are

corresponding to an amount of 0.68% of the ketene, at 5 ° in a glass frit flask equipped with thermal

a speed of 64 kg (1.52 kg mol) ketene, meter and reflux condenser are located at a

140.4 kg (2.42 kg mol) acetone and 0.438 kg reaction temperature of 65 to 68 ⁰ C within

(0.0043 kg mol) of difluorophosphoric acid per hour for 3V ₂ hours with a total of 210 g (5.0 mol) of ketene

directed. This corresponds to a molar ratio to a rate of 60 g (1.43 mol) of ketene per

directed ketene total acetone = 1: 1.63. That fed up 55 hours. This corresponds to a molar

Adjusting molar ratio of absorbed ketene-ratio of fed-in ketene-n-butyraldehyde = 1: 1.7.

total acetone is 1: 1.65, with the acetone feed. The catalyst concentration is 0.15%, based on

only when a reaction temperature of the sum of the reactants is reached, from the

73 ° C is started. The ketene absorption is the reaction mixture is obtained by distillation

10 422.5 kg (248.3 kg mol), that is 99.3% of the tensile 60 182.5 g (1.6 mol) of n-butenyl acetate at the boiling point

directed Ketens. The residence time is 4.3 hours. 128 ° C at 735 mm of mercury, accordingly

The catalyst concentration is 0.22%, based on a conversion of the fed ketene into

the sum of the respondents. The continuous butenyl acetate of 32%
nuierlich withdrawn reaction product is continuously

to the extent of its formation with the sodium provided. Example 8

acetate neutralized. After termination of the reaction In a manner analogous to Example 2, in

are made from 34 136 kg reaction product, that is a reactor with a capacity ^{of 700 cm 3 inside}

99.5% of the material used, at the beginning of which a total of 630 g (15.0MoI) of ketene,

215Og (16.5 mol) of ethyl acetoacetate using a total of 8.6 g (0.085 mol) difluorophosphoric acid as a catalyst, equivalent to a molar ratio of fed initiated ketene ethyl acetoacetate = 1: 1.1, at a reaction temperature of 65 to 7O ⁰ C for implementation brought. The residence time is 1.26 hours. The catalyst ^{concentration is 0.31 0} I ₀ , based on the sum of the reactants. The ketene absorption is quantitative. After neutralization by vacuum distillation, the reaction mixture gives the enol acetates of ethyl acetoacetate with a boiling point of 94 ^° C. at 10 mm of mercury in a yield of 95%, based on consumed ethyl acetoacetate.

Example 9

In a mixture of 500.6 g (5.0 mol) of acetylacetone and 0.6 g of difluorophosphoric acid, which is in a fritted glass flask equipped with a thermometer and reflux condenser, are at a reaction temperature of 65 to 70 ° C within 3V ₂ hours a total of 210 g (5.0 mol) of ketene fed at a rate of 60 g (1.43 mol) of ketene per hour. This corresponds to a molar ratio of supplied ketene to acetylacetone = 1: 1. The catalyst concentration is 0.08%, based on the sum of the reactants. Corresponding to a 70% conversion of the ketene to the Monoenolacetat of acetylacetone is obtained from the reaction mixture by vacuum distillation, 497.0 g (3.5 mol) of acetylacetone Monoenolacetat of boiling point 82 to 84 ^C C at 10 mm of mercury.

Example 10

In a mixture of 500.6 g (5.0 mol) of acetylacetone and 1.5 g of difluorophosphoric acid, which, is equipped with thermometer and reflux condenser in a fritted glass flask, are at a reaction temperature of 65 to 7O ⁰ C within 420 hours total , 4 g (10.0 mol) of ketene fed at a rate of 60 g (1.43 mol) of ketene per hour. This corresponds to a molar ratio of supplied ketene to acetylacetone = 2: 1. The catalyst concentration is 0.16%, based on the sum of the reactants. Ish from the Reaktionsgem obtained by vacuum distillation of 320.0 g (2.25 mol) of boiling point Monoenolacetat to 84 ⁰ C at 10 mm of mercury and 156.0 g (0.85 mol) of di-enolacetate of boiling point 114 ° C in mm Mercury column. This corresponds to a 45 ° / o conversion of acetylacetone in the Monoenolacetat and a 17 _^0/0 by weight conversion of acetylacetone in the di-enolacetate.

Claims (3)

PATENT CLAIMS: 1. A process for the preparation of enol acetates by reacting enolizable carbonyl compounds with ketene in the presence of a phosphoric acid catalyst, characterized in that the catalyst used is difluorophosphoric acid or a mixture of equimolecular amounts of difluorophosphoric acid and monofluorophosphoric acid or the reaction product used in the reaction of 1 Moles of phosphorus pentoxide and 3 moles of hydrogen fluoride are formed and consist of equimolecular amounts of difluorophosphoric acid and monofluorophosphoric acid. 2. The method according to claim 1, characterized in that in a temperature range between 20 and 110 ⁰ C, preferably between 60 and 80 ° C, is carried out. 3. The method according to claim 1 and 2, characterized in that a catalyst concentration of 0.01 to 2 ⁰ I ₀ , based on the sum of the reactants, is used. Considered publications:
German patent specification No. 1 014 104. 109 759/420 1.62