Organic Reactions Volume 4 - Sciencemadness Dot Org

370 ORGANIC REACTIONS
added. The reaction vessel is placed in an oil bath, and a rapid stream
of hydrogen is passed into the solution. A faint development of hydrogen
chloride commences at 70°; the rate of evolution increases with rise
in temperature and reaches a maximum at 180°, at which temperature
the reduction is carried out. The hydrogen chloride formation drops off
^ quite suddenly after five to ten hours, and at the
point where it becomes faint the reaction is interrupted.
After the reaction mixture has cooled to room temperature,
the decalin solution is decanted from the
catalyst, diluted with 600 ml. of ether, and shaken
with an equal volume of saturated sodium bisulfite
solution for twelve hours. The voluminous precipitate
of bisulfite compound is filtered and is washed
thoroughly with ether. The bisulfite compound is
decomposed by boiling with excess dilute aqueous
sodium carbonate, and the aldehyde is extracted with
ether. The ether solution is dried, and the ether is
evaporated. The aldehyde crystallizes immediately.
It contains traces of decalin, which are washed out
with petroleum ether. It is distilled at reduced pressure
(oil pump). The average yield is 90%. The
aldehyde can be recrystallized from benzene by the
FIG. 1
addition of petroleum ether to give a product that
melts at 79.5-80°.
2- and 9-Phenanthraldehydes. These are prepared in the same manner
as the 3-aldehyde except that 4 parts of decalin are employed in
the reduction of 1 part of acid chloride. The yield of the 2-isomer, m.p.
59-59.5°, recrystallized from benzene-petroleum ether, is 70%. The
yield of the 9-isomer, m.p. 100.5-101°, recrystallized from ethanol, is
90%.
TABLES OF ACID CHLORIDES REDUCED BY THE ROSENMUND
METHOD
In the following tables are summarized the compounds whose reduction
by the Rosenmund method is reported in the literature to November,
1947. Acid chlorides in which the functional group is attached to
an aliphatic or hydroaromatic residue are listed in Table I; aromatic
and heterocyclic acid chlorides are listed in Tables II and III, respectively.