Rodniks

Rodniks is a term encountered in some scientific writings to denote free radicals in chemistry. In standard English usage, the preferred term is radical; rodnik is largely seen in transliterations from non-English sources. A radical is any atom, molecule, or ion that contains at least one unpaired electron. This unpaired electron makes radicals highly reactive and often paramagnetic, driving rapid reactions to achieve electron pairing with other species.

Radicals are formed by processes such as homolytic bond cleavage, redox reactions, photolysis, or radiolysis. Many radicals are transient, but some are stabilized by resonance, conjugation, or steric protection, giving rise to persistent radicals such as allyl, benzyl, or TEMPO.

Radicals are typically detected and studied by electron spin resonance (ESR or EPR) spectroscopy, which senses unpaired electron spins. Their chemistry follows characteristic patterns, including hydrogen-atom abstraction, addition to multiple bonds, and radical–radical coupling. Oxygen-centered radicals (for example hydroxyl OH•) and peroxyl radicals ROO• play prominent roles in atmospheric chemistry and biology, while carbon-centered radicals (R•) drive many organic transformations.

Applications and relevance of radicals span polymerization, combustion, and broad areas of organic synthesis where radical reactions enable bond formation under mild or selective conditions. In biology and environmental science, reactive oxygen species, a subset of radicals, influence cellular damage and degradation pathways. Safety concerns arise from their high reactivity, potential to initiate unwanted side reactions, and oxidative damage to living systems and materials. See also radical, ESR, radical polymerization, and reactive oxygen species.