Croconic Acid

[488-86-8] C5H2O5 (MW 142.07) InChI = 1S/C5H2O5/c6-1-2(7)4(9)5(10)3(1)8/h6-7H InChIKey = RBSLJAJQOVYTRQ-UHFFFAOYSA-N (reagent used in the construction of near-infrared-absorbing dyes) Physical Data: mp >300 °C. Solubility: soluble in THF, alcohols, and water. Form Supplied in: widely available as white powder. Purification: croconic acid can be recrystallized by first dissolving in hot THF, followed by the addition of an equal volume of ether after cooling. Anhydrous croconic acid is obtained by drying for several hours at 100 °C at 10−3 torr. Handling, Storage, and Precautions: croconic acid should be stored in dark; the reagent is somewhat hygroscopic.