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Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids. [1] A variety of oxidants can be used.
The international pictogram for oxidizing chemicals. Dangerous goods label for oxidizing agents. An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "accepts"/"receives" an electron from a reducing agent (called the reductant, reducer, or electron donor).
These iodine compounds are hypervalent because the iodine atom formally contains in its valence shell more than the 8 electrons required for the octet rule. Hypervalent iodine oxyanions are known for oxidation states +1, +3, +5, and +7; organic analogues of these moieties are known for each oxidation state except +7.
It is a colourless gas that reacts with oxygen to give water and iodine. Although it is useful in iodination reactions in the laboratory, it does not have large-scale industrial uses, unlike the other hydrogen halides. Commercially, it is usually made by reacting iodine with hydrogen sulfide or hydrazine: [4] 2 I 2 + N 2 H 4 4 HI + N 2
The mechanism of carbonyl oxidation by iodine(III) reagents varies as a function of substrate structure and reaction conditions, but some generalizations are possible. Under basic conditions, the active iodinating species are iodine(III) compounds in which any relatively acidic ligands on iodine (such as acetate) have been replaced by alkoxide. [1]
In contrast, two-step sequence via a borane (vide supra) that is subsequently oxidized to the alcohol with hydrogen peroxide is of synthetic utility. The synthetic utility of Grignard oxidations can be increased by a reaction of Grignard reagents with oxygen in presence of an alkene to an ethylene extended alcohol. [22]
[4] [10] One such method makes use of hydrogen peroxide as the oxidizer and iodine or an iodine salt as a catalyst for the oxidation occurring in a polar solvent; e.g. isopropyl alcohol. [11] When heated to near its melting point, 1,4-benzoquinone sublimes, even at atmospheric pressure, allowing for an effective purification.
There are two reactions occurring simultaneously in the solution. In the first, slow reaction, iodine is produced: H 2 O 2 + 2 I − + 2 H + → I 2 + 2 H 2 O. In the second, fast reaction, iodine is reconverted to two iodide ions by the thiosulfate: 2 S 2 O 2− 3 + I 2 → S 4 O 2− 6 + 2 I −. After some time the solution changes color to ...