Q: In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
This kind of molecule is detected by the CIDNP effect in NMR spectroscopy, and examples of them include the nitroso component of Fremy's salt and TEMPO. They take part in reactions like NMP, ATRP, and RAFT, or reversible addition-fragmentation chain transfer. One of these based on naphthalene shows up as five quintets in ESR spectroscopy, which is especially suited to their study. The most prominent biological one is counteracted by its namesake dismutase, superoxide, and the anti-Markovnikov addition of HBr to an alkene can occur via one of these. Other reactions involving them tend to consist of initiation, propagation, and termination. FTP, name these highly reactive molecules characterized by an unpaired electron in their outer shell.
A:
Science