Ethyl acetate acetoacetate

Ethyl acetoacetate may be prepared by the action of sodium upon dry ethyl acetate and decomposition of the resulting sodio compound with dilute acetic acid. Most samples of ethyl acetate contain some ethyl alcohol and it is usually assumed that sodium ethoxidc is the condensing agent ... 

The formation of ethyl acetoacetate is an example of a general reaction knowu as the acetoacetlc ester condensation in which an ester having hydrogen on the a-carbon atom condenses with a second molecule of the same ester or with another ester (which may or may not have hydrogen on the a-carbon atom) in the presence of a basic catalyst (sodium, sodium ethoxide, sodamide, sodium triphenylmethide) to form a p-keto-ester. The mechanism of the reaction may be illustrated by the condensation of ethyl acetate with another molecule of ethyl acetate by means of sodium ethoxide. ... 

This is an alternative experiment to the actual preparation of the ester and will give the student practice in conducting a distillation under diminished pressure. Commercial ethyl acetoacetate generally contains inter alia some ethyl acetate and acetic acid these are removed in the following procedure. 

Simple esters (e.g., ethyl acetate) undergo the acetoacetic ester condense tion (compare Section 111,151). The effective condensing agent is sodium ethoxide, produced by the action of sodium upon traces of alcohol present in the ester ... 

The formation of acyloins (a-hydroxyketones of the general formula RCH(OH)COR, where R is an aliphatic residue) proceeds best by reaction between finely-divided sodium (2 atoms) and esters of aliphatic acids (1 mol) in anhydrous ether or in anhydrous benzene with exclusion of oxygen salts of enediols are produced, which are converted by hydrolysis into acyloins. The yield of acetoin from ethyl acetate is low (ca. 23 per cent, in ether) owing to the accompanying acetoacetic ester condensation the latter reaction is favoured when the ester is used as the solvent. Ethyl propionate and ethyl ji-butyrate give yields of 52 per cent, of propionoin and 72 per cent, of butyroin respectively in ether. 

Pentanedione can also be produced by the condensation of acetone with ethyl acetate (312—317), or by the condensation of ethyl acetoacetate and ketene (318—321). Other methods are known (322,323). 

When larger runs are made the yields increase thus 2000 cc. of ethyl acetate and 200 g. of sodium give 515-568 g. of ethyl acetoacetate. From a run of this size it is possible to recover about 700 cc. of ethyl acetate. Approximately a proportionate recovery is obtained in smaller runs. 

Ethyl acetoacetate has been prepared from ethyl acetate by the action of sodium/ sodium ethylate/ sodamide/ and calcium. ... 

Ethyl acetosuccinate has been prepared by the interaction of ethyl sodio-acetoacetate and ethyl chloroacetate or broino-acetate. The method given above is a modification of that given by Conrad. ... 

On treatment with alkoxide bases, esters undergo self-condensation to give a p-keto ester and an alcohol. Ethyl acetate, for exanple, undergoes a Claisen condensation on treatment with sodium ethoxide to give a p-keto ester known by its common nane ethyl ace-toacetate (also called acetoacetic ester) ... 

Ethyl acetoacetate (acetoacetic ester), available by the Claisen condensation of ethyl acetate, has properties that make it a useful starting material for the preparation of ketones. These properties are... 

The formation of ethyl acetoacetate occurs, according- to Claisen, in four steps. The presence of a small quantity of alcohol gives lise to sodium ethylate, which forms an additive compound with ethyl acetate. The latter unites with a second molecule of ethyl acetate yielding the sodium salt of ethyl acetoacetate, and splitting off alcohol, which reacts with fresh metallic sodium. The sodium salt on acidifying passes into the tautomeric (ketonic) form of acetoacetic ester. 

Ethyl Acetoacetate. -The e. planation of the manner in which this substance is produced has been given in the account of the preparation. The result was anived at, not by the iscila-tion of the intermediate compound formed by the union of ethyl acetate with sodium ethylate, but by analogy with the behaviour of benzoic methyl ester with sodium benzylate, which gave the same additive product as that obtained by combining benzoic benzyl ester with sodium methylate, showing that such combinations could occur,... 

Esters, like aldehydes and ketones, are weakly acidic. When an ester with an a- hydrogen is treated with 1 equivalent of a base such as sodium ethoxide, a reversible carbonyl condensation reaction occurs to yield a /3-keto ester. For example, ethyl acetate yields ethyl acetoacetate on base treatment. This reaction between two ester molecules is known as the Claisen condensation reaction. (We ll use ethyl esters, abbreviated "Et," for consistency, but other esters will also work.)... 

Ethyl acetate, ethyl acetoacetate from, 888-889 NMR spectrum of, 823... 

An important group of acylation reactions involves esters, in which case the leaving group is alkoxy or aryloxy. The self-condensation of esters is known as the Claisen condensation.216 Ethyl acetoacetate, for example, is prepared by Claisen condensation of ethyl acetate. All of the steps in the mechanism are reversible, and a full equivalent of base is needed to bring the reaction to completion. Ethyl acetoacetate is more acidic than any of the other species present and is converted to its conjugate base in the final step. The (3-ketoester product is obtained after neutralization. 

The reaction was monitored by TLC (eluent petroleum ether ethyl acetate 75 25). The methyl acetoacetate was UV active, stained yellow with p-anisaldehyde, R 0.5. No starting material remained after 48 hours. 

The quality of the ethyl acetate used is of great importance for the success of this experiment since the completely alcohol-free compound reacts only very slowly with sodium even on warming, whilst, on the other hand, material containing much alcohol reacts readily with sodium but gives varying and sometimes poor yields of ethyl acetoacetate. 

Finely powdered sodamide (34 g.),a which is kept in a closed container, is added gradually in small portions to a mixture of 120 c.c. of ethyl acetate (purified as for the preparation of ethyl acetoacetate) and 32 c.c. of dry acetone. During the addition of the sodamide the mixture is cooled in a freezing mixture. The flask is provided with a cork or rubber stopper carrying a calcium chloride tube. A vigorous evolution of ammonia at once begins. After all the soda-... 

The Mechanism of the Ethyl Acetoacetate Synthesis—Before the tautomerism of ethyl acetoacetate is discussed we must consider the mechanism of its formation, which for decades has been the subject of lively discussion and was conclusively explained only in recent years (Scheibler). It has been found that even the C=0-group of the simple carboxylic esters, although in other respects inferior in activity to the true carbonyl group, can be enolised by alkali metals. Thus ethyl acetate is converted by potassium into the potassium salt of the tautomeric enol with evolution of hydrogen ... 

It is not only the esters of organic acids which combine, in the manner of the ethyl acetoacetate synthesis , with the enolates of ketones and of esters an analogous behaviour is shown by the esters of nitrous and nitric, acids. The process which leads to the formation of isonitroso-and atinitro-compounds yields products fundamentally similar to those already described just as with ethyl acetate the group CO.CHs enters, so here, the NO- and N02-groups are involved, and enolise " exactly as does >O=0 ... 

Acetamido-4-amino-6-chloro-s-triazine, see Atrazine Acetanilide, see Aniline, Chlorobenzene, Vinclozolin Acetic acid, see Acenaphthene, Acetaldehyde, Acetic anhydride. Acetone, Acetonitrile, Acrolein, Acrylonitrile, Aldicarb. Amyl acetate, sec-Amyl acetate, Bis(2-ethylhexyl) phthalate. Butyl acetate, sec-Butyl acetate, ferf-Butyl acetate, 2-Chlorophenol, Diazinon. 2,4-Dimethylphenol, 2,4-Dinitrophenol, 2,4-Dinitrotoluene, 1,4-Dioxane, 1,2-Diphenylhydrazine, Esfenvalerate. Ethyl acetate, Flucvthrinate. Formic acid, sec-Hexyl acetate. Isopropyl acetate, Isoamyl acetate. Isobutyl acetate, Methanol. Methyl acetate. 2-Methvl-2-butene. Methyl ferf-butvl ether. Methyl cellosolve acetate. 2-Methvlphenol. Methomvl. 4-Nitrophenol, Pentachlorophenol, Phenol. Propyl acetate. 1,1,1-Trichloroethane, Vinyl acetate. Vinyl chloride Acetoacetic acid, see Mevinphos Acetone, see Acrolein. Acrylonitrile. Atrazine. Butane. 

Ethyl Acetoacetate. 250 g of ethyl acetate are shaken with a sodium carbonate solution, separated and allowed to stand for 23 hours over anhydrous calcium chloride. Filter and distill taking care to keep moisture or water from the reaction. 

The Claisen reaction (sometimes Claisen condensation) is formally the base-catalysed reaction between two molecules of ester to give a P-ketoester. Thus, from two molecules of ethyl acetate the product is ethyl acetoacetate. 

Addition of ethyl acetate to a specimen having a transaminase activity of 47 units was responsible for the following increases in enzyme activity 10 mg/100 ml, 60 units 20 mg/100 ml, 77 units 40 mg/100 ml, 107 units and 80 mg/100 ml, 150 units. Transaminase activity in these specimens determined by another method ranged from 32 to 34 units (C7). Thus, when serum from patients with ketosis is assayed for aspartate aminotransferase activity by the diazo method, false elevations of activity may be recorded due to reaction of acetoacetic acid. In Table 11 are shown some values obtained by the diazo method and by an ultraviolet NADH NAD aspartate aminotransferase technique (B12). Examination of the medical records of these patients indicated that they were either diabetics who were in ketosis or individuals who were eating very poorly and had some degree of starvation ketosis. Similar elevations have been observed in patients receiving p-aminosalicylic acid (G6). 

The enolate anion attacks the carbonyl carbon of a second molecule of ester and gives a P-ketoester. Thus, the Claisen condensation is a nucleophilic acyl substitution reaction. Eor example, two molecules of ethyl acetate condense together to form the enolate of ethyl acetoacetate, which upon addition of an acid produces ethyl acetoacetate (P-ketoester). 

Nucleophilic attack of the enolate anion to the carhonyl carhon of another ethyl acetate gives an alkoxide tetrahedral intermediate. The resulting alkoxide reforms the carhonyl group hy ejecting the ethoxide anion. This ethoxide anion deprotonates the a-hydrogen, and produces a new enolate anion of the resulting condensed product, which is protonated in the next step upon acidification during work-up and yields the ethyl acetoacetate. 

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