次锰酸钾
| 次锰酸钾 | |
|---|---|
| |
| IUPAC名 potassium manganate(V) potassium tetraoxidomanganate(3−) | |
| 性质[1] | |
| 化学式 | K3MnO4 |
| 摩尔质量 | 236.23 g·mol⁻¹ |
| 外观 | 淡蓝色固体 |
| λmax | 670 nm (ε = 900 dm3 mol−1 cm−1) nm |
| 相关物质 | |
| 其他阴离子 | 锰酸钾 高锰酸钾 |
| 若非注明，所有数据均出自标准状态（25 ℃，100 kPa）下。 | |
次锰酸钾（K3MnO4）是一种淡蓝色的盐，它是很少见的次锰酸盐。
制备
[编辑]最早制得的次锰酸盐是Na3MnO4·10H2O，但后来发现它实际上是Na3MnO4·0.25NaOH·10H2O。[2]
- MnO−
4 + SO2−
3 + H2O → MnO3−
4 + SO2−
4 + 2 H+
- MnO−
- 2 MnO2−
4 + H2O2 + 2 OH− → 2 MnO3−
4 + O2 + 2 H2O
- 2 MnO2−
- 2 MnO2−
4 + C
8H
7O−
3 + 2 OH− → 2 MnO3−
4 + C
8H
5O−
3 + 2 H2O
- 2 MnO2−
- 2 MnO2 + 3 OH− → MnO3−
4 + MnO(OH) + H2O
- 2 MnO2 + 3 OH− → MnO3−
性质
[编辑]次锰酸盐在无水和无二氧化碳的条件下能稳定存在。在水溶液中因歧化而不稳定，尤其是在碱性溶液中。[3][4]估计pH=14的水溶液中它的标准电极电势如下所示：[6][7][8]
- MnO2−
4 + e− ⇌ MnO3−
4 E = +0.27 V - MnO3−
4 + e− + 4 H2O ⇌ MnO2 + 6 OH− E = +0.96 V
歧化反应被认为经过质子化的中间体，[8]因为HMnO2−
4 ⇌ MnO3−
4 + H+的酸度系数的负对数，即pKa约为13.7 ± 0.2。[9]然而，K3MnO4能与Ca2Cl(PO4)共结晶并析出，使得人们可以用紫外可见吸收光谱来研究锰(V)酸根离子。[3][10]
用高锰酸钾或锰酸钾氧化有机化合物时，次锰酸根离子经常作为中间体出现。[2]
参考资料
[编辑]- ^ 1.0 1.1 Lee, Donald G.; Chen, Tao, Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of oxidation of organic compounds by high-valent transition metal oxides, J. Am. Chem. Soc., 1993, 115 (24): 11231–36, doi:10.1021/ja00077a023.
- ^ 2.0 2.1 《无机化学丛书》第九卷：锰分族、铁系、铂系. 北京: 科学出版社. : P46–47. ISBN 7-03-002238-6.
- ^ 3.0 3.1 3.2 3.3 Cotton, F. Albert; Wilkinson, Geoffrey, Advanced Inorganic Chemistry 4th, New York: Wiley: 746, 1980, ISBN 0-471-02775-8.
- ^ 4.0 4.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements. Oxford: Pergamon. 1984: 1221–22. ISBN 0-08-022057-6..
- ^ Lee, Donald G.; Chen, Tao, Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds, J. Am. Chem. Soc., 1989, 111 (19): 7534–38, doi:10.1021/ja00201a039.
- ^ Weast, Robert C. (编). CRC Handbook of Chemistry and Physics 62nd. Boca Raton, FL: CRC Press. 1981: D-134. ISBN 0-8493-0462-8..
- ^ Manganese – compounds – standard reduction potentials, WebElements, [2010-06-26], （原始内容存档于2021-01-17）.
- ^ 8.0 8.1 Sekula-Brzezińska, K.; Wrona, P. K.; Galus, Z., Rate of the MnO4−/MnO42− and MnO42−/MnO43− electrode reactions in alkaline solutions at solid electrodes, Electrochim. Acta, 1979, 24 (5): 555–63, doi:10.1016/0013-4686(79)85032-X.
- ^ Rush, J. D.; Bielski, B. H. J., Studies of Manganate(V), -(VI), and -(VII) Tetraoxyanions by Pulse Radiolysis. Optical Spectra of Protonated Forms, Inorg. Chem., 1995, 34 (23): 5832–38, doi:10.1021/ic00127a022.
- ^ Carrington, A.; Symons, M. C. R., Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions, J. Chem. Soc., 1956: 3373–80, doi:10.1039/JR9560003373.
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