Organic Syntheses, CV 2, 541
Submitted by Charles D. Hurd and R. N. Meinert.
Checked by W. L. McEwen and W. H. Carothers.
1. Procedure
One hundred grams (125 cc., 1.7 moles) of n-propyl alcohol, b.p.
96–96.6°, is placed in a
2-l. three-necked, round-bottomed flask fitted with a
mercury-sealed stirrer (Note
1), a
dropping funnel, and a
60-cm. bulb condenser (Note
2) set at an angle of 45°. Water at 60° is kept circulating through this condenser. A
condenser set for downward distillation is connected to the top of the first condenser. Cold water circulates through the second condenser. By means of an
adapter, the lower end of the second condenser is fitted to a
receiver which is cooled with ice water.
The alcohol in the flask is heated to boiling, stirred, and a mixture of
164 g. (0.56 mole) of potassium dichromate,
120 cc. of concentrated sulfuric acid (2.2 moles), and 1 l. of water is added through the dropping funnel. The addition takes about thirty minutes, and during this time the contents of the flask are kept vigorously boiling. After all the oxidizing mixture has been added, the contents of the flask are boiled for fifteen minutes to distil the last of the aldehyde. The
propionaldehyde which collects in the receiver is dried with
5 g. of anhydrous sodium sulfate and fractionally distilled. The yield of
propionaldehyde boiling at
48–55°, and having a refractive index of 1.364 (Note
3), is
44–47 g. (
45–49 per cent of the calculated amount).
2. Notes
1. The yield of
propionaldehyde depends largely upon the efficiency of the stirrer.
2. The purpose of the first condenser is to condense and return to the flask any
propyl alcohol which escapes.
3. The recorded value for the index of refraction (
N20°D) is 1.3636.
3. Discussion
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