Ascorbic acid

Chemistry

Acidity

The hydroxyls (OH) next to the double bond are enols. One enol loses an electron pair, becoming an oxonium group (=OH2+), by creating a double bond to the carbon. Simultaneously, the carbon-carbon double bond (between the enols) transfers its electrons to form a double bond to the next (two-oxygen) carbon. To give way, the double bond electrons of the carbonyl are received by the carbonyl's oxygen, to produce an enolate. The oxonium promptly deprotonates to produce a carbonyl, and this loss of protons gives ascorbic acid its acidity. The overall reaction is enol deprotonation to produce an enolate, where the negative charge of the resulting enolate counterion is delocalized over the system of carbonyl (C=O) and the double bond (C=C). This delocalization makes the counterion more stable and less likely to regain the proton.

Related Topics:
Double bond - Enol - Electron pair - Oxonium - Enolate - Deprotonate - Carbonyl - Acidity

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Tautomerism

Ascorbic acid also rapidly inconverts into two unstable diketone tautomers by proton transfer, although it is the most stable in the enol form. The proton of the enol is lost, and reacquired by electrons from the double bond, to produce a diketone. There are two possible forms, 1,2-diketone and 1,3-diketone.

Related Topics:
Inconvert - Diketone - Tautomer - Proton transfer

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