https://doi.org/10.1351/goldbook.S05878
In certain reactions in solution a
transient
radical
will interact with a diamagnetic
reagent
to form a more persistent
radical. The product radical accumulates to a concentration where detection and, frequently, identification are possible by EPR/ESR spectroscopy
. The key reaction is usually one of attachment
; the diamagnetic
reagent
is said to be a 'spin trap' and the persistent
product radical is then the 'spin adduct
'. The procedure is referred to as spin trapping
, and is used for monitoring
reactions involving the intermediacy of reactive
radicals at concentrations too low for direct observation. Typical spin traps are C-nitroso compounds
and nitrones
, to which reactive radicals will rapidly add to form nitryl radicals. A quantitative development, in which essentially all reactive radicals generated in a particular system are intercepted, has been referred to as 'spin counting'. Spin trapping
has also been adapted to the interception of radicals generated in both gaseous and solid phases. In these cases the spin adduct is in practice transferred to a liquid solution for observation in order to facilitate interpretation of the EPR/ESR spectra of the radicals obtained.