Citrazinic acid explained

Citrazinic acid (CZA) is a heterocyclic compound consisting of a dihydropyridine ring derived with a carboxylate group. The yellow solid exists as multiple tautomers, and it frequently forms dimers.^[1]

Citrazinic acid is commonly formed in citric acid based carbon nanodots (CND). It is responsible for the blue light found in citric acid CNDs. The wavelengths of light emitted by citrazinic in CNDs can be shifted by changing the pH of the solution.^[2]

Preparation

Citrazinic acid can be prepared creating a solution of citric acid and toluenesulfonic acid, which forms a 1,3-diester. That solution, when added to a heated ammonia solution results in citrazinic acid.^[3]

Notes and References

1. Stagi L, Mura S, Malfatti L, Carbonaro CM, Ricci PC, Porcu S, Secci F, Innocenzi P . 6 . Anomalous Optical Properties of Citrazinic Acid under Extreme pH Conditions . ACS Omega . 5 . 19 . 10958–10964 . May 2020 . 32455216 . 7241015 . 10.1021/acsomega.0c00775 .
2. Mocci F, Olla C, Cappai A, Corpino R, Ricci PC, Chiriu D, Salis M, Carbonaro CM . 6 . Formation of Citrazinic Acid Ions and Their Contribution to Optical and Magnetic Features of Carbon Nanodots: A Combined Experimental and Computational Approach . Materials . 14 . 4 . 770 . February 2021 . 33562081 . 10.3390/ma14040770 . 7914458 . 2021Mate...14..770M . free .
3. Baizer MM, Dub M, Gister S, Steinberg NG . Synthesis of isoniazid from citric acid . Journal of the American Pharmaceutical Association . 45 . 7 . 478–480 . July 1956 . 13345683 . 10.1002/jps.3030450714 .