Deprotonation

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Deprotonation is the removal of a proton (H+) from a molecule, forming the conjugate base.

The relative ability of a molecule to give up a proton is measured by its pKa value. A low pKa value indicates that the compound is acidic and will easily give up its proton to a base. The pKa of a compound is determined by many things, but the most significant is the stability of the conjugate base, which is determined mainly by the ability (or inability) of the conjugated base to stabilize the negative charge. The negative charge is stabilized when it is distributed on a large surface or a long chain. One of the mechanisms that distribute the negative charge on a longer chain or a ring is resonance. The solvent can also assist in the stabilization of the negative charge on a conjugated base.

Bases used to deprotonate depend on the pKa of the compound. When the compound is not particularly acidic, and, as such, the molecule does not give up its proton easily, a base stronger than the commonly known hydroxides is required. Hydrides are one of the many types of powerful deprotonating agents. Common hydrides used are sodium hydride and potassium hydride. The hydride forms hydrogen gas with the proton from the other molecule. However, the production of hydrogen also means that deprotonation using agents that release hydrogen is dangerous and should be done in an inert atmosphere (e.g., nitrogen), as the hydrogen can ignite with the oxygen in the air.

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