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For oxidations to the aldehydes and ketones, two equivalents of chromic acid oxidize three equivalents of the alcohol: 2 HCrO 4 − + 3 RR'C(OH)H + 8 H + + 4 H 2 O → 2 [Cr(H 2 O) 6] 3+ + 3 RR'CO. For oxidation of primary alcohols to carboxylic acids, 4 equivalents of chromic acid oxidize 3 equivalents of the alcohol. The aldehyde is an ...
This kind of chromic acid may be used as a cleaning mixture for glass. Chromic acid may also refer to the molecular species, H 2 CrO 4 of which the trioxide is the anhydride. Chromic acid features chromium in an oxidation state of +6 (and a valence of VI or 6). It is a strong and corrosive oxidizing agent and a moderate carcinogen.
Oxidative cyclizations of olefinic alcohols to cyclic ethers may occur via [3+2], [2+2], [1] or epoxidation mechanisms. Insights into the mechanism is provided by structure-reactivity, implicating direct epoxidation by the chromate ester. [1] Subsequent epoxide opening and release of chromium leads to the observed products.
The red line on the predominance diagram is not quite horizontal due to the simultaneous equilibrium with the chromate ion. 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.
Sulfuric acid is not an oxidizing agent, but the sulfate ion is a very weak oxidizing agent. Since sulfur is in its maximum oxidation state in the sulfate ion, it cannot act as a reducing agent. Cu + 2 H 2 SO 4 → SO 2 + 2 H 2 O + SO 2−
Stages in the oxidation of primary alcohols to carboxylic acids via aldehydes and aldehyde hydrates. Almost all industrial scale oxidations use oxygen or air as the oxidant. [2] Through a variety of mechanisms, the removal of a hydride equivalent converts a primary or secondary alcohol to an aldehyde or ketone, respectively.
Collins reagent is especially useful for oxidations of acid sensitive compounds. Primary and secondary alcohols are oxidized respectively to aldehydes and ketones in yields of 87-98%. [5] Like other oxidations by Cr(VI), the stoichiometry of the oxidations is complex because the metal undergoes 3e reduction and the substrate is oxidized by 2 ...
The first example of an oxidative phenol coupling in synthetic chemistry can be traced to Julius Löwe’s 1868 synthesis of ellagic acid, accomplished by heating gallic acid with arsenic acid. [ 8 ] In the synthesis of complex organic compounds , oxidative phenol couplings are sometimes employed.