Organic Syntheses, Coll. Vol. 2, p.541 (1943); Vol. 12, p.64 (1932).
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.
per cent of the calculated amount).
The yield of propionaldehyde
depends largely upon the efficiency of the stirrer.
The purpose of the first condenser is to condense and return to the flask any propyl alcohol
The recorded value for the index of refraction (N20°D
) is 1.3636.
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