2,3-Butanedione
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
(Diacetyl), CH3COCOCH2 86.09 CAS RN®: 431-03-8.—Bright yellow to yellowish-green liquid. Soluble in water. Miscible with
alcohol and with ether. Boils at about 88°.
Assay
Hydroxylamine hydrochloride solution: Dissolve 20 g of hydroxylamine hydrochloride in 40 mL of water, and dilute with alcohol to 400 mL.
Add, with stirring, 300 mL of 0.5 N alcoholic potassium hydroxide VS, and filter. Discard after 2 days.
Procedure: Transfer about 1 g, accurately weighed, to a glass-stoppered, 250-mL flask, add 75.0 mL of Hydroxylamine hydrochloride solution, and insert the stopper in the flask. Reflux the mixture for 1 hour, then cool to room temperature. Add bromophenol blue TS, and titrate with 0.5 N hydrochloric acid VS to a greenish-yellow endpoint. [Note—Alternatively, the solution may be titrated potentiometrically to a pH of 3.4.] Perform a blank test with the same quantities of reagent used for the test specimen, and make any necessary correction. Each mL of 0.5 N
hydrochloric acid is equivalent to 43.05 mg of CH COCOCH . Not less than 97% of CH3COCOCH2 is found.
Congealing Temperature〈651〉: between −2.0° and −5.5°.
Refractive Index〈831〉: between 1.3935 and 1.3965, at 20°.
Specific Gravity〈841〉: about 0.98.
