Propiedades Fiscio Quimicas

Páginas: 4 (930 palabras) Publicado: 7 de abril de 2012
Organic Syntheses, Coll. Vol. 1, p.235 (1941); Vol. 6, p.36 (1926).

[Acetoacetic acid, ethyl ester]

Submitted by J. K. H. Inglis and K. C. Roberts.
Checked by C. S. Marveland F. E. Kendall.

1. Procedure
In a 2-l. round-bottomed flask, fitted with an efficient reflux condenser, are placed 500 g. (531 cc.,
5.7 moles) of ethyl acetate (Note 1), and 50 g. (2.2 atoms)of clean sodium wire or finely sliced sodium
(Note 2) is added. The reaction is at first quite slow, and must be started by warming on a water bath
(Note 3). After the reaction is once started itproceeds vigorously and cooling is then necessary in order
to avoid loss of material through the condenser. When the rapid reaction slows down, the reaction
mixture is heated on a water bath until thesodium has completely dissolved. This usually requires about
one and one-half hours. At this stage the reaction mixture should be a clear red liquid with a green
This solution isthen cooled and made slightly acid by adding about 275 cc. of 50 per cent acetic
acid (Note 4). Salt is added if necessary to cause the ester to separate. The ester layer is separated, dried
overcalcium chloride, and fractionally distilled under reduced pressure from a modified Claisen flask
(p. 130).
The yield of ester boiling at 76–80°/18 mm. is 105–110 g. (28–29 per cent of the theoreticalamount
based on the ethyl acetate) (Note 5).

2. Notes
1. The grade of ethyl acetate used is very important. It must be entirely free from water and should
contain about 2–3 per cent of alcohol.The absolute ethyl acetate of the U. S. Industrial Alcohol
Company is satisfactory for use. If this grade is not available, ordinary ethyl acetate may be purified by
washing it with twice its volumeof water and drying over fused potassium carbonate, from which it is
decanted, and used directly. The ethyl acetate purified in this way contains enough ethyl alcohol to
allow the reaction to run...
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