ロジゾン酸二ナトリウム

解説5,6-dihydroxy-5-cyclohexene-1,2,3,4-tetraone disodium salt．C6O6Na2(213.94)．ロジゾン酸二ナトリウム, 2,3,5,6-テトラヒドロキシ-p-ベンゾキノンを水酸化ナトリウム溶液中で空気酸化して得られる．紫色の針状結晶．Ba2＋ の沈殿試薬．また，Ba，Sr，Pb，Snなどの点滴試薬としても用いられる．"Ba2＋ の検出限界は0.25 μg，限界濃度1：200000．容量分析法による Ba2＋，SO42－定量の指示薬ともなる．[CAS 523-21-7] 森北出版「化学辞典（第2版）

用途Ba, Sr, Pb, Sn, SO4の検出、定量。

使用Sodium rhodizonate dibasic can be employed as a reactant in the synthesis of: Dihydroxyquinone carbonate by cyclocondensation reaction with phosgene. Zwitterionic systems by condensation of heteroaryl-boronic acids.

純化方法The free acid is obtained by acidifiying and extracting with Et2O, drying (MgSO4), filtering, evaporating and distilling in a vacuum (b 155-160o/14mm). The free acid solidifies on cooling, and the colourless crystals can be recrystallised from tetrahydrofuran/pet ether or *C6H6. It forms a dihydrate m 130-140o. The pure di Na salt is formed by dissolving the acid in 2 equivalents of NaOH and evaporating in a vacuum. It forms violet crystals which give an orange solution in H2O that is unstable for extended periods even at 0o, and should be prepared freshly before use. Salts of rhodizonic acid cannot be purified by recrystallisation without great loss due to conversion to crotonate, so that the original material must be prepared anew if pure salt is required. It can be washed with NaOAc solution, then EtOH, to remove excess NaOAc, dried under vacuum and stored in the dark. [UV and tautomerism: Schwarzenbach & Suter Helv Chim Acta 24 617 1941, Polarography: Preisler & Berger J Am Chem Soc 64 67 1942, Souchay & Taibouet J Chim Phys 49 C108 1952, Beilstein 8 H 535, 8 II 572, 8 III 4214, 8 IV 3609.]