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Although insoluble in water, it reacts with acid to produce salts of hydrated chromium ions such as [Cr(H 2 O) 6] 3+. [11] It is also attacked by concentrated alkali to yield salts of [Cr(OH) 6] 3−. When heated with finely divided carbon or aluminium, it is reduced to chromium metal: Cr 2 O 3 + 2 Al → 2 Cr + Al 2 O 3
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 ...
4 CrO 3 → 2 Cr 2 O 3 + 3 O 2. It is used in organic synthesis as an oxidant, often as a solution in acetic acid, [9] or acetone in the case of the Jones oxidation. In these oxidations, the Cr(VI) converts primary alcohols to the corresponding carboxylic acids and secondary alcohols to ketones. The reactions are shown below: Primary alcohols ...
4 HCrO 4 − + 3 RCH 2 OH + 16 H + + 11 H 2 O → 4 [Cr(H 2 O) 6] 3+ + 3 RCOOH. The inorganic products are green, characteristic of chromium(III) aquo complexes. [2] Like many other oxidations of alcohols by metal oxides, the reaction proceeds via the formation of a mixed chromate ester: [3] [4] These esters have the formula CrO 3 (OCH 2 R) −
Commonly three electrons are added to a chromium atom, reducing it to oxidation state +3. In acid solution the aquated Cr 3+ ion is produced. Cr 2 O 2− 7 + 14 H + + 6 e − → 2 Cr 3+ + 7 H 2 O ε 0 = 1.33 V. In alkaline solution chromium(III) hydroxide is produced. The redox potential shows that chromates are weaker oxidizing agent in ...
Potassium hypochromate decomposes in water to form chromium(III) oxide and potassium chromate when alkali is not present or low. [1] Potassium hypochromate also reacts with acids such as hydrochloric acid to form chromium(III) oxide, potassium chromate, and potassium chloride: [2] 6 K 3 CrO 4 + 10 HCl → 4 K 2 CrO 4 + Cr 2 O 3 + 5 H 2 O + 10 KCl
Fractional oxidation states are often used to represent the average oxidation state of several atoms of the same element in a structure. For example, the formula of magnetite is Fe 3 O 4, implying an average oxidation state for iron of + 8 / 3 . [17]: 81–82 However, this average value may not be representative if the atoms are not ...
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]