Dehydroacetic Acid
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C8H8O4 168.15

Keto 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.
Identification , Infrared Absorption 197K.
Heavy metals, Method II 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.
Melting range, Class I 741: between 109 and 111.
Residue on ignition 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, B.A.
(EM105) Excipient Monographs 1
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 1222
Pharmacopeial Forum: Volume No. 33(4) Page 703