Dehydroacetic Acid
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168.15Keto form: 2H-Pyran-2,4(3H)-dione, 3-acetyl-6-methyl-.
3-Acetyl-6-methyl-2H-pyran-2,4(3H)-dione
[520-45-6].Enol form: 2H-Pyran-2-one, 3-acetyl-4-hydroxy-6-methyl-.
3-Acetyl-4-hydroxy-6-methyl-2H-pyran-2-one
[771-03-9].» Dehydroacetic Acid contains not less than 98.0 percent and not more than 100.5 percent of C8H8O4, calculated on the dried basis.
Packaging and storage—
Preserve in well-closed containers. No storage requirements specified.
USP Reference standards 
11
—
11—
USP Dehydroacetic Acid RS 
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Identification, Infrared Absorption 197K
.
197K
.
Heavy metals, Method II 231:
not more than 0.001%.
231:
not more than 0.001%.
Loss on drying 731:
Dry it at 80
for 4 hours: it loses not more than 1.0% of its weight.
731:
Dry it at 80 for 4 hours: it loses not more than 1.0% of its weight.
Melting range, Class I 741:
between 109 and 111.
741:
between 109 and 111.
Residue on ignition 281:
not more than 0.1%.
281:
not more than 0.1%.
Assay—
Transfer about 500 mg of Dehydroacetic Acid, accurately weighed, into a 250-mL conical flask, dissolve it in 75 mL of neutralized alcohol, add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS to a pink endpoint that persists for not less than 30 seconds. Each mL of 0.1 N sodium hydroxide is equivalent to 16.82 mg of C8H8O4.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Robert H. Lafaver, M.S.
Scientific Liaison 1-301-816-8335 |
(EXC2010) Monographs - Excipients |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 1778
Pharmacopeial Forum: Volume No. 33(4) Page 703