Organic Syntheses, CV 4, 932
Submitted by H. B. Hass and Myron L. Bender
1.
Checked by Arthur C. Cope and Malcolm Chamberlain.
1. Procedure
Eleven and one-half grams (0.5 g. atom) of sodium is dissolved in
500 ml. of absolute ethanol in a
1-l. round-bottomed flask.
Forty-six grams (0.52 mole) of 2-nitropropane is added, then
92.5 g. (0.50 mole) of o-xylyl bromide (Note
1). The flask is attached to a
reflux condenser connected to a drying tube and shaken at intervals for 4 hours. The reaction mixture, originally at room temperature, becomes warm spontaneously, and a white precipitate of
sodium bromide forms (Note
2).
After a reaction period of 4 hours the
sodium bromide is separated by filtration and the
ethanol is removed by distillation on a
steam bath. The residue of product and
sodium bromide is dissolved in
100 ml. of ether and 150 ml. of water. The
ether layer is washed with two
50-ml. portions of 10% sodium hydroxide solution to remove any
acetoxime and excess
2-nitropropane and is then washed with 50 ml. of water. The
ether layer is separated and is dried with
15 g. of anhydrous sodium sulfate, and the
ether is removed by distillation on a
steam bath.
The crude product is distilled from a
Claisen flask under reduced pressure. The yield of
o-tolualdehyde boiling at
68–72°/6 mm.,
n25D 1.5430, is
41–44 g. (
68–73%) (Note
3).
2. Notes
1.
o-Xylyl bromide may be obtained from the Eastman Kodak Company or may be prepared by the light-catalyzed bromination of
o-xylene.
2
2. The solution is originally supersaturated with the sodium salt of
2-nitropropane, and a precipitate of this salt may be mistaken for
sodium bromide.
3. This is a general method for the preparation of substituted benzaldehydes. The following aldehydes have been prepared by the same general procedure.
3
3. Discussion
This preparation is referenced from:
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