Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

342 ALUMINIUM CHLOKIDB
immediately after they are prepared (cf. also ZerevitinofFs determination
on p. 84).
The great variety of synthetic processes included in the Grignard
reaction may be illustrated by the production of diphenlymethyl
carbinol and consequently of unsymmetrical diphenylethylene :
1. From benzophenone and methyl magnesium bromide :
/OH
(C6H5)2.CO + CH3.Mg.Br —•> (C6H5)2:C< .
2. From ethyl acetate and phenyl magnesium bromide :
CH3.COOC2H5 + 2C6H5.Mg.Br —>
H
Related to the Grignard synthesis is that of Reformatzky in which
zinc is used to condense the esters of a-halogenated fatty acids with
ketones, e.g. :
(CH3)2:C=CH.CH2.CH2.CO.CH3 + Zn + C1H2C.CO2R
Methvlheptenone
OH
> (CH3)2:C=CH.CH2.CH2.C.CH2.CO2R
H3
CH3
- H '° (CH3)2C:CH.CH2.CH2.C(CH3):CH.CO2H
hydrolysis Geranic acid
THE FRIEDEL-GRAFTS SYNTHESIS
Aluminium Chloride.—For the success of a Friedel-Crafts synthesis
it is essential that the quality of the aluminium chloride used
as catalyst should be beyond reproach. Commercial preparations
are often partially decomposed and unfit for use in consequence of
the entrance of moisture into insufficiently closed containers. In
order to make sure, a small sample should be heated over a flame in a
test tube held obliquely ; the whole, or at least the bulk, of the
chloride should sublime. Preparations which are not too seriously
decomposed can be made fit for use by resublimation.
If it is necessary to prepare the aluminium chloride in the laboratory
the following method should be used. 1
Connect a wide (3-5-4 cm.) hard glass tube, e.g. a tube used for
combustions by Dennstedt's method, by means of a cork with a wide-
1 It is recommended that aluminium chloride obtained during preparative work
in the inorganic department of the laboratory should be employed for syntheses of
the type here described.