Quinolinium Dichromate

Light yellow to Brown powder to crystal.

Quinolinium dichromate (QDC) is found to be a mild reagent for the oxidation of organic compounds. It is particularly effective for oxidizing primary and secondary alcohols to their corresponding aldehydes and ketones, respectively. Like other chromium(VI) reagents, QDC is suitable for laboratory research and development as well as for chemical and pharmaceutical synthesis processes.

Quinolinium dichromate was prepared according to the procedure describe by Balasubramanian et al. [5]
Synthesis of Quinolinium Dichromate: Quinidine (28 mL, 0.2 mol) was added slowly to a cooled solution of chromium trioxide (CrO₃, 20 g, 0.2 mol) in water (20 mL). After stirring for 0.5 hours, the reaction mixture was diluted with acetone (40 mL) and cooled to -15 °C. The yellow crystals that formed were collected by filtration, washed with acetone, and then recrystallized from water. The product was dried under vacuum for approximately 2 hours. Yield: 88%. Melting point: 150–151 °C.

Quinolinium Dichromate, (C9H8N)2[Cr2O7], crystallizes in the monoclinic space group P21/c, with eight cations and four anions in the unit cell. The quinolinium cations and a dichromate anion are connected through N—H...O and C—H...O intermolecular hydrogen bonds and by aromatic π–π-stacking interactions. The dichromate geometry is normal, with a Cr—O(bridging)—Cr angle of 135.1 (2)°.

[1] Sundar, T. V., et al. "Quinolinium dichromate,[C9H7NH+] 2· Cr2O72−." Structure Reports 59.6 (2003): m327-m329.
[2] K. SATISH BABU . Kinetics and mechanism of quinolinium chlorochromate mediated oxidation of sugar alcohols in Bronsted acid media[J]. Chemical Data Collections, 2020, 25: Article 100332. DOI:10.1016/j.cdc.2019.100332.
[3] NEBAHAT DEGIRMENBASI  Beytiye O. Quinaldinium Fluorochromate and Quinaldinium Dichromate: Two New and Efficient Reagents for the Oxidation of Alcohols.[J]. ChemInform, 2004, 35 35. DOI:10.1002/chin.200435039.
[4] BERNADETTE KUOTSU. Quinolinium Dichromate Oxidation of Diols: A Kinetic Study[J]. The Journal of Organic Chemistry, 1996, 61 25: 8875-8877. DOI:10.1021/jo961079m.
[5] Rajalakshmi, K., T. Ramachandramoorthy, and S. Srinivasan. "Oxidation of cyclic ketones by benzyl triethylammonium chlorochromate by 1, 10-phenanthroline as catalyst—kinetic and mechanistic study." J. Chem. Pharm. Res 4 (2012): 894-900.