htranszfer

Htranszfer is a term used in chemistry to describe processes that move hydrogen atoms or protons between chemical species. In many contexts it is written as hydrogen transfer or H-transfer and encompasses several related mechanistic classes.

Hydrogen atom transfer (HAT) involves the movement of a neutral hydrogen atom, including its electron, and often proceeds through radical intermediates. Hydride transfer refers to the movement of a hydride (H−), delivering two electrons to an acceptor; this type is common in metal-catalyzed reductions and biological redox reactions. Proton transfer concerns the movement of a proton (H+) without an accompanying electron, and proton-coupled electron transfer (PCET) describes processes where proton and electron transfer occur either simultaneously or in a coupled sequence.

Mechanistic aspects vary: HAT can be concerted or stepwise and is influenced by bond strengths, radical stability, and solvent; hydride transfer depends on hydricity and the relative affinity of donor and acceptor; PCET combines aspects of both. In biological systems, enzymes use cofactors such as NADH or metal centers to effect hydride or proton transfers, while synthetic chemistry employs catalysts to control selectivity and rate.

Applications include organic synthesis, where hydrogen transfer enables hydrofunctionalization and radical transformations; bioenergetics and metabolism, where hydrogen transfers power redox reactions and energy storage; and materials science, where PCET mechanisms inform the design of solar fuels and electrochemical devices.

See also: hydrogen atom transfer, hydride transfer, proton transfer, proton-coupled electron transfer, radical chemistry.