SODIUM DICHROMATE, NATRIUM DIKROMAT
Sodium dichromate is an inorganic compound with the formula Na2Cr2O7. Usually presented in the form of the dihydrate salt Na2Cr2O7 · 2H2O. In fact, all chromium ore is processed by conversion to sodium dichromate and all chromium-based compounds and materials are made from this salt. [1] In terms of reactivity and appearance, sodium dichromate and potassium dichromate are very similar. However, the sodium salt is twenty times more soluble than the potassium salt (49 g / L at 0 ° C) and its equivalent weight is also lower. [2]
Reaction
The dichromate and chromate salts are oxidizing agents. In order to whiten the skin material, sodium dichromate is first reduced with sulfur dioxide.
In the field of organic synthesis, [2] this compound oxidizes the C-H bonds of benzyl and allyls to their carbonyl derivatives. For example, 2,4,6-trinitrotoluene is oxidized to its carboxylic acids. [3] Similarly, 2,3-dimethylnaphthalene is oxidized by Na2Cr2O7 to 2,3-naphthalendicarboxylic acid. [4]
Secondary alcohols are oxidized to ketones, for example menthol to mentona; [5] dihydrocholesterol becomes cholestanone: [6]
3 R2CHOH + Cr2O72− + 2 H + → 3 R2C = O + Cr2O3 + 4 H2O
Compared to the potassium salt, sodium dichromate's advantage is its large solubility in water and polar solvents such as acetic acid.
When heated strongly, sodium dichromate decomposes to form sodium chromate, chromium (III) oxide and oxygen: 4 Na2Cr2O7 → 4 Na2CrO4 + 2 Cr2O3 + 3 O2 [3] [7] Sodium dichromate can be used to convert fluorene to fluorenone.
Work safety
Like other hexavalent chromium compounds, sodium dichromate is considered dangerous. It is also known that this compound is a carcinogen. [8]
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