Organic Syntheses, Coll. Vol. 1, p.471 (1941); Vol. 4, p.59 (1925).
In a dry 3-l. flask
, fitted with a mercury-sealed stirrer
, a 500-cc. dropping funnel
, and a condenser
provided at its upper end with a drying tube
containing a mixture of calcium chloride and soda-lime (Note 1)
, is placed 48.6 g. (2 atoms) of magnesium turnings
. There are then added 200 cc. of dry ether
, a small crystal of iodine
, and about 25 cc. of a solution of 253 g. (230 cc., 2 moles) of freshly distilled benzyl chloride
in 1 l. of dry ether
. If the reaction does not start at once, the flask is partially immersed in a bath containing water heated to about 40°. As soon as the ether
begins to boil, and reaction sets in, the bath is removed and stirring is commenced. The remainder of the benzyl chloride
can be added during the course of one-half hour if the reaction is regulated by cooling the greater part of the flask by immersion in ice water (Note 2)
. The reaction will continue for about fifteen minutes after all the benzyl chloride
has been added, and then the mixture is refluxed gently for about fifteen minutes.
To the stirred benzylmagnesium chloride
is then added 616 g. (522 cc., 4 moles) of freshly distilled diethyl sulfate (Note 3)
. The addition of diethyl sulfate
is so regulated that gentle refluxing takes place throughout the reaction. Once reaction is started with a few cubic centimeters of diethyl sulfate
, it is necessary to cool the reaction flask by ice water in order to complete addition within about one hour. When all the ester
has been added, stirring is continued with gentle boiling for fifteen minutes (Note 4)
The cooled mixture is next poured, with stirring, upon a mixture of 1 kg. of crushed ice, 1 l. of water, and 200 cc. of concentrated hydrochloric acid
. After stirring a few minutes to dissolve the sludge, the major part of the water layer is siphoned off and the ethereal solution is separated. The water layer is washed once with about 50 cc. of ether
, and this washing is added to the ethereal solution of n-propylbenzene
. The ether
is removed by distillation from a water or steam bath
through a fractionating column
. The residue is poured into 1 l. of 10 per cent sodium hydroxide solution in about 50 per cent alcohol
, and this mixture is refluxed for one hour (Note 5)
. After the n-propylbenzene
is thrown out by the addition of a large volume of water, the hydrocarbon
is separated, combined with an ether
extract of the aqueous layer, dried by standing over 10–15 g. of solid potassium hydroxide
, and fractionally distilled through an efficient column
. The yield of n-propylbenzene
, distilling at 155–160°
, is 165–180 g.
per cent of the theoretical amount).
The function of the calcium chloride
is to absorb any moisture and carbon dioxide
which might diffuse into the reaction flask. The deleterious effect of another constituent of the atmosphere, oxygen
, may be decreased by first sweeping out the flask with dry nitrogen or hydrogen
. The initial use of a dry inert atmosphere may also be supplemented by the use of a trap1
to exclude the air, particularly in those operations requiring extensive periods.
If the diethyl sulfate
is dark in color it should be washed, prior to distillation, with ice water and then with a sodium bicarbonate
solution until all free acid is removed.
At the end of this time a negative color test shows that the Grignard reagent has been used up.
The solution is refluxed with alcoholic alkali to decompose any unaltered diethyl sulfate
This preparation is referenced from:
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved