Reactive intermediates

thumb|120px|The tert-butyl cation is a relatively stable carbenium ion.

In organic chemistry, a carbanion is an anion with a lone pair attached to a tervalent carbon atom. This gives the carbon atom a negative charge.

thumb|60px|Methylene (compound)|Methylene is the simplest carbene. In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.

radical composed by one atom of oxygen and one atom of hydrogen

molecular entity that is formed from the reactants (or preceding intermediates) and reacts further to give the directly observed products of a chemical reaction

thumb|115px|right|The generic structure of a nitrene group

In organic chemistry, arynes and benzynes are a class of highly reactive chemical species derived from an aromatic ring by removal of two substituents. Arynes are examples of didehydroarenes (1,2-didehydroarenes in this case), although 1,3- and 1,4-didehydroarenes are also known. Arynes are examples of alkynes under high strain.

thumb|right|300px|Resonance structures of an enolate anion.

class of ions

any cation that has a pentavalent carbon atom

class of ions

class of compounds

charged free radical species

A reductone is a special class of organic compounds. They are enediols with a carbonyl group adjacent to the enediol group, i.e. RC(OH)=C(OH)-C(O)R. The enediol structure is stabilized by the resonance resulting from the tautomerism with the adjacent carbonyl. Therefore, the chemical equilibrium produces mainly the enediol form rather than the keto form.

Fluoromethylidyne is not a stable chemical species but a metastable radical containing one highly reactive carbon atom bound to one fluorine atom with the formula CF. The carbon atom has a lone-pair and a single unpaired (radical) electron in the ground state.

Class of reactive intermediate species based on nitrogen and isoeletronic with carbene

Cyclopentyne is a cycloalkyne containing five carbon atoms in the ring. Due to the ideal bond angle of 180° at each atom of the alkyne but the structural requirement that the bonds form a ring, this chemical is a highly strained structure, and the triple bond is highly reactive. The triple bond easily undergoes both [2+2] and [4+2] cycloaddition reactions. Unlike benzyne, which undergoes a [2+2] addition with loss of stereochemistry at the alkene partner, cyclopentyne reacts with alkenes with retention of geometry of the partner, an example of the relevance of orbital symmetry even for highly