Heptaldehyde enol acetate

A. Heptaldehyde enol acetate. A mixture of 28S g. (335 ml., 2.5 moles) of heptaldehyde (Note 1), 612 g. (566 ml., 6 moles) of acetic anhydride, and 49 g. (0.5 mole) of powdered potassium acetate is placed in a 2-1. fl2isk fitted with a reflux condenser. The flask is heated in an oil bath kept at 155-160° for 1 hour. The mixture is then allowed to cool, placed in a 2-1. separatory funnel, washed several times with warm water (Note 2) to remove the excess acetic anhydride, and finally washed with 5% sodium carbonate solution (Note 3). The resultant oil is fractionated under reduced pressure through an cflicient column... 

Note 4). The initial fraction consists of pure heptaldehyde followed by heptaldehyde containing heptaldehyde enol acetate. The fraction boiling at 88-90°/17 mm. is pure enol acetate, 1.4295-1.4305 df 0.880-0.884. The yield is 175-195 g. 

The reaction mixture consists of unchanged heptaldehyde, heptaldehyde enol acetate, heptaldehyde diacetate, and a small amount of polymerized material. The proportion of free heptaldehyde and heptaldehyde diacetate depends upon the time of heating, longer periods of heating favoring the formation of the diacetate. An eflBcient fractionating column, preferably of the Whitmore-Fenske type, should be used in order to obtain the enol acetate free of the heptaldehyde and heptaldehyde diacctatc impurities. The checkers used a Whitmore-Fenske type column of about six theoretical plates. 

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