alkoxyl

Alkoxyl, in chemistry, refers to the alkoxyl radical species with the general formula RO•. It is an oxygen-centered radical derived from alcohols, ethers, or related oxygen-bearing compounds. Alkoxyl radicals are short‑lived, highly reactive intermediates that participate in a variety of oxidation and decomposition processes.

The radical is primarily characterized by its unpaired electron located on the oxygen atom, although resonance can distribute some electron density toward adjacent atoms in certain structures. Their reactivity arises from the high electrophilicity of the oxygen-centered radical and their ability to engage in hydrogen-atom transfer, addition to double bonds, or fragmentation reactions. Common generation methods include homolytic cleavage of O–H or C–O bonds in alcohols or ethers, photolysis, and redox or catalytic oxidation reactions.

Two principal reaction channels define alkoxyl chemistry. First, hydrogen abstraction from neighboring substrates to give an alcohol (ROH) and a new radical on the substrate. Second, beta-scission (cleavage of the carbon–carbon bond adjacent to oxygen), which converts the alkoxyl radical into a carbonyl compound plus a new radical, or in the case of tert‑alkoxyls, into acetone and a methyl radical, for example: (CH3)3CO• → CH3COCH3 + CH3•. These pathways drive many oxidation and degradation processes in organic chemistry, combustion, and atmospheric chemistry.

Alkoxyl radicals play roles in polymer oxidation, lipid peroxidation, and the broader radical-initiated oxidation of organic matter. They are studied to understand product distributions, reaction kinetics, and the mechanisms of oxidative aging in materials and environments. See also alkyl radicals and other alkoxyl/alkoxy-related species.