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It can be prepared by treating chromium metal with fluorine at 400 °C and 200 bar pressure. The peroxochromate(V) is another example of the +5 oxidation state. Potassium peroxochromate (K 3 [Cr(O 2) 4]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures. This red brown compound is stable at room temperature but ...
The hydrogen chromate ion may be protonated, with the formation of molecular chromic acid, H 2 CrO 4, but the pK a for the equilibrium H 2 CrO 4 ⇌ HCrO − 4 + H + is not well characterized. Reported values vary between about −0.8 and 1.6. [4] The dichromate ion is a somewhat weaker base than the chromate ion: [5]
It was popularized for selective oxidation of primary and secondary alcohols to carbonyl compounds. Collins reagent is a solution of the same CrO 3 (pyridine) 2 but in dichloromethane. The Ratcliffe variant of Collins reagent relates to details of the preparation of this solution, i.e., the addition of chromium trioxide to a solution of ...
A typical PCC oxidation involves addition of an alcohol to a suspension of PCC in dichloromethane. [6] [7] [8] The general reaction is: 2 [C 5 H 5 NH][CrO 3 Cl] + 3 R 2 CHOH → 2 [C 5 H 5 NH]Cl + Cr 2 O 3 + 3 R 2 C=O + 3 H 2 O. For example, the triterpene lupeol was oxidized to lupenone: [9]
At pH < 5.89 (pH < pK 1) the hydrogen chromate ion is predominant in dilute solution but the dichromate ion is predominant in more concentrated solutions. Predominance diagrams can become very complicated when many polymeric species can be formed as, for example, with vanadate, [4] molybdate [1] and tungstate. [1]
Chromyl chloride can be prepared by the reaction of potassium chromate or potassium dichromate with hydrogen chloride in the presence of concentrated sulfuric acid, followed by distillation. [3] [4] K 2 Cr 2 O 7 + 6 HCl → 2 CrO 2 Cl 2 + 2 KCl + 3 H 2 O. The sulfuric acid serves as a dehydration agent.
It can be prepared by treating chromium metal with fluorine at 400 °C and 200 bar pressure. The peroxochromate(V) is another example of the +5 oxidation state. Potassium peroxochromate (K 3 [Cr(O 2) 4]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures. This red brown compound is stable at room temperature but ...
Sodium dichromate is the inorganic compound with the formula Na 2 Cr 2 O 7. However, the salt is usually handled as its dihydrate Na 2 Cr 2 O 7 ·2 H 2 O . Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. [ 1 ]