In a 2-l. round-bottomed, three-necked flask
fitted with a stirrer
and two large-bore condensers
are placed 200 cc. of 50 per cent nitric acid
and 0.25 g. of vanadium pentoxide
. The flask is heated to 65–70° in a water bath
in the water), and 1 cc. of cyclopentanone
is added. Oxidation is indicated by the production of brown fumes. The water bath is removed, and 42 g. (less the 1 cc.) of the cyclic ketone
is added from a dropping funnel
through the condenser at the rate of a drop every three seconds. The heat of the reaction keeps the flask at about 70°. If the temperature drops, oxidation ceases until the ketone has accumulated, when it may proceed almost explosively. In such a case, or if the temperature is higher, much succinic acid
is formed. After addition has been completed, the water bath is replaced and the mixture heated to boiling. The contents of the flask are poured into an evaporating dish
), and the volume reduced one-half. When cold, the acid is filtered and the operation repeated twice; the last time the acid is yellowish, and the color is removed by washing with dilute hydrochloric acid
. The crude glutaric acid
is white and weighs 50–55 g.
per cent); m.p. 92–94°
. If any succinic acid
is present owing to lack of proper control, it separates in the first crop. It is more convenient to allow the mother liquors from several runs to accumulate and work them up separately; from each run 2–3 g.
more of glutaric acid
may be so obtained. Further purification is accomplished, if desired, by crystallization from benzene
. The acid as prepared above always contains traces of nitric acid
, but is satisfactory for conversion into the anhydride. If the catalyst is omitted, the yield is less by 10
per cent. (C. F. H. Allen and W. L. Ball, private communication).