= Stable radical
An unpaired <Electron> does not set a universal <reaction rate>. A <stable radical> can retain radical character during isolation and storage under specified conditions; a persistent <radical (chemistry)> survives long enough under specified conditions to be observed. These descriptions concern lifetime and handling, rather than immunity to every possible <chemical reaction>. <DPPH> is a practical counterexample to the claim that all <free radicals> react immediately.
Two mechanisms help explain persistence. Spreading electronic character over several <chemical atoms>, represented by <chemical resonance>, can lower the <energy> relative to a localized description. Bulky surrounding groups can impede approach to a reactive site and slow recombination. Lower <energy> and slower <chemical kinetics> are different advantages: neither alone guarantees a long lifetime. A primary computational study explicitly separates these effects, using electronic and geometric descriptors; it does not directly measure every predicted lifetime.<A quantitative metric for organic radical stability and persistence using thermodynamic and kinetic features by Shree Sowndarya S. V. and others>[A quantitative metric for organic radical stability and persistence using thermodynamic and kinetic features, Shree Sowndarya S. V., Peter C. St. John and Robert S. Paton, 2021: Abstract and Introduction, thermodynamic stabilization versus kinetic persistence]{ref}
Back to article page
