In chemistry, a hydrogen atom abstraction or hydrogen atom transfer (HAT) is any

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and break ...

in which a hydrogen free radical (neutral hydrogen atom) is abstracted from a

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

according to the general equation: :X^\bullet + H-Y -> X-H + Y^\bullet Examples of HAT reactions are oxidative reactions in general, hydrocarbon

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combust ...

, and reactions involving

cytochrome P450 Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compo ...

containing an iron(V)-oxo unit. The abstractor (X•) is usually a radical species itself, but it may also be a

closed-shell In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom ...

species such as chromyl chloride. HAT can take place through proton-coupled electron transfer. A synthetic example is found in iron zeolites, which stabilize alpha-oxygen.

References

{{Reflist Chemical reactions Reaction mechanisms