Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

384 ADIPIC ALDEHYDE FROM CYCLOHEXENE
carbon can be recrystallised from a little alcohol. Yield 5 g.
(almost theoretical).
Benzoin can be reduced to dibenzyl in the same way.
For the replacement of oxygen by hydrogen in ketones and aldehydes
the method of Kishner and Wolff is used as often as is that of Clemmensen.
In the former method the hydrazone or semicarbazone of the carbonyl
compound is heated for several hours—preferably in the presence of
hydrazine hydrate—in a sealed tube or autoclave with sodium ethoxide
at about 160°. The explanation of the reaction is that, under
the catalytic influence of the ethoxide, the hydrazone is transformed
into a diimine which then decomposes in the same way as does
phenyldiimine (p. 286):
T> T> T>
\ = N — N H 2 >- \ C H — N = N H >
The reverse process, conversion of >CH2 into >CO succeeds in the
case of ketones with selenium dioxide. Thus acetone may be directly
oxidised to meihylglyoxal. This oxidising agent has been used very
frequently recently because of the great variety of ways in which it can
be applied.
4. ADIPIC ALDEHYDE FROM CYCLOHEXENE BY OZONISATION 1
Carry out the ozonisation in a thin-walled gas wash-bottle
(capacity 400 c.c.) with an inlet tube widened out to a bell shaped
opening or twisted to a spiral. Connect the bottle to the ozoniser
by bending the inlet tube of the former at a right angle so that
it can be inserted into the delivery tube of the ozoniser, which is
fitted with a mercury seal.
Dissolve 16 g. of cyclohexene in 200 c.c. of pure, dry ethyl
acetate, 2 cool the solution in the bottle with an efficient ice-salt
mixture to - 20° (or, better, with solid carbon dioxide in acetone to
- 50° to - 70°) and then connect to the ozoniser.
During the ozonisation keep the freezing mixture in an insulated
jar (see p. 2) in order to maintain the best possible cooling efEect.
If an ozoniser with at least five discharge tubes is used a very vigorous
current of ozonised oxygen can be employed and the operation completed
in from four to seven hours. For example, if twenty litres
1 F. G. Fischer and K. Loewenberg, Ber., 1933, 66, 666.
2 Shake ethyl acetate four times with an equal volume of water, dry over
calcium chloride, and distil.