Organic Syntheses, Coll. Vol. 3, p.656 (1955); Vol. 29, p.78 (1949).
In a 16-cm. evaporating dish
are placed 42.2 g. (0.2 mole) of 3-nitrophthalic acid
50 ml. of water, and a few drops of phenolphthalein
indicator solution. The mixture is made faintly alkaline to phenolphthalein
with about 66 ml. (0.4 mole) of 6 N sodium hydroxide
solution (Note 1)
, the last portions of which are added slowly with good stirring so that the end point may be observed. The color of the phenolphthalein
is discharged by the addition of 0.2–0.3 g. of the 3-nitrophthalic acid
, and 26.0 g. (0.2 mole) of hydrazine sulfate2
is added. The solution is evaporated to dryness over a sand bath
, with stirring at the latter part of the evaporation (Note 2)
, and the residual solid is cooled, ground in a mortar
to a fine powder, and placed in a 200-ml. conical flask
with 25 ml. of tetralin (Note 3)
. The mixture is heated at 160–170° for 3 hours and allowed to cool. After the addition of 50 ml. of benzene
the solid is collected on a Büchner funnel
and pressed down well, and most of the benzene
is removed by suction. The solid is then washed with two 25-ml. portions of ether
and allowed to stand in the air until the odor of ether
is no longer detectable. The resulting material, weight 62–68 g., is an equimolar mixture of sodium sulfate
, and it may be used directly for preparing 5-amino-2,3-dihydro-1,4-phthalazinedione
(luminol, p. 69
For purification, the crude material is suspended in 600–700 ml. of boiling water, and solid sodium carbonate
is added in portions until the nitro compound has dissolved. Decolorizing carbon
is added cautiously, and the suspension is boiled for a few minutes and filtered. The clear red-brown filtrate is acidified with concentrated hydrochloric acid
, and the 5-nitro-2,3-dihydro-1,4-phthalazinedione
is precipitated as a cream-colored flocculent solid. The solution is allowed to cool to room temperature, and the solid is separated by filtration and dried. The product thus obtained weighs 31–32 g.
) and has a melting point of 315–316°
(dec.) when determined with the Kullman copper block (Note 4)
The strength of the sodium hydroxide
solution is not critical; the equivalent amount of a solution of a different concentration may be used.
It is wise to cover the hand with a cloth or a glove while stirring, for the hot mixture may spatter if the heating is too rapid. The evaporation may be finished by transferring the evaporating dish to an oven
shortly after the solid begins to separate. It is necessary to continue the evaporation until the solid is completely dry.
In an optional procedure the dry powder is heated in an oven at 160–170° for 3 hours.
This preparation is referenced from:
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