Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

CHAPTBK IX
THE GEIGNAED AND FEIEDEL-CEAFT8 SYNTHESES.
OEGANIC EADICLES
THE GRIGNARD REACTION
1. PREPARATION OF ALCOHOLS
(a) BENZOHYDROL FROM BENZALDEHYDE AND PHENYL
MAGNESIUM BROMIDE
A SMALL, dry, round-bottomed flask is fitted with a branched neck
attachment and the oblique branch is connected with a reflux condenser
closed at the upper end with a calcium chloride tube.
Through the stopper of the upright branch a dropping funnel with a
long outlet tube is inserted. The flask contains 3-2 g. of magnesium
shavings, on to which a mixture of 20 g. of pure, constant-boiling
bromobenzene and 50 c.c. of absolute ether is dropped gradually
from the funnel. After about a quarter of the mixture has been
added the operation is interrupted until evolution of heat and ebullition
of the ether indicate the beginning of the reaction. Occasionally
there is an obstinate delay ; by holding a basin with warm
water under the flask, or, better by dropping in a particle of iodine,
the reaction can be started with rapidity and certainty. When
preparing the phenyl magnesium bromide solution it is important
to keep the process in check by cooling from time to time and by
regulating the inflow of bromobenzene so that the reaction just
continues of its own accord. The bromobenzene which adheres to
the dropping funnel is washed into the flask with a little absolute
ether. When most of the metal has dissolved and the reaction
becomes noticeably slacker, the solution is boiled for some time
by dipping the flask into a basin of warm water until only a few
particles of magnesium remain in suspension.
The solution is now cooled in ice-water and 10-6 g. of freshly
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