hydridedonor

A hydridedonor refers to a chemical species that can readily donate a hydride ion (H⁻). A hydride ion is a hydrogen atom with an extra electron, giving it a negative charge. Hydridedonors are crucial reagents in organic synthesis, particularly in reduction reactions where they transfer a hydride ion to an acceptor molecule, typically a carbonyl compound or an alkene.

Common hydridedonors include metal hydrides such as sodium borohydride (NaBH₄) and lithium aluminum hydride (LiAlH₄). These compounds are characterized by the presence of a metal-hydrogen bond where the hydrogen atom carries a partial or full negative charge. The strength of the hydridedonor's ability to donate a hydride ion is influenced by the electronegativity of the metal and the overall structure of the compound.

The mechanism of hydride transfer generally involves the nucleophilic attack of the hydride ion on an electrophilic center in the substrate molecule. This process effectively reduces the substrate by adding hydrogen atoms. For example, in the reduction of a ketone to a secondary alcohol, a hydridedonor delivers a hydride ion to the carbonyl carbon, followed by protonation of the alkoxide intermediate. The choice of hydridedonor depends on the specific functional group to be reduced and the desired selectivity of the reaction. Some hydridedonors are more reactive and less selective than others.