A<unk>  (also known as a stable<unk>  is a particular<unk>  demonstrating particular stability despite being a reactive intermediate.  Instability in these<unk> s involves reactivity with substrates, or dimerisation (see Wanzlick equilibrium).<unk> s can exist in the singlet state or the triplet state, with the singlet state<unk> s being the more stable.
Persistent carbene
Halogenated ether
Heterocyclic compound
Organic peroxide
Inhalant
Bifunctional catalyst
Xylene
Dimethyl sulfide