Description Preparation Note Tetrahyrofurane/Water/Pyridine/Iodine 90.54/9.05/0.41/0.43 (v/v/v/w) Other Notes Oxidizer solution, containing tetrahydrofuran (THF), pyridine, iodine and water, is applied to oxidize the chemically unstable trivalent phosphorous triester linkage formed in the coupling reaction to a stable pentavalent phosphate triester. Iodine functions as a mild oxidant and water functions as an oxygen donor.