Quaternary carbon

A quaternary carbon is a carbon atom bound to four other carbon atoms.^[1] For this reason, quaternary carbon atoms are found only in hydrocarbons having at least five carbon atoms. Quaternary carbon atoms can occur in branched alkanes, but not in linear alkanes.^[2]

	primary carbon	secondary carbon	tertiary carbon	quaternary carbon
General structure (R = Organyl group)
Partial Structural formula

quaternary carbon
Structural formula of neopentane (quaternary carbon is highlighted red)

Synthesis

Bis-Phenol A synthesis from acetone and phenol

The formation of chiral quaternary carbon centers has been a synthetic challenge. Chemists have developed asymmetric Diels–Alder reactions,^[3] Heck reaction, Enyne cyclization, cycloaddition reactions,^[4] C–H activation, Allylic substitution,^[5] Pauson–Khand reaction,^[6] etc. to construct asymmetric quaternary carbon atoms.

One of the most industrially important compounds containing a quaternary carbon is bis-phenol A (BPA). The central atom is a quaternary carbon. Retrosynthetically, that carbon is the central atom of an acetone molecule before condensation with two equivalents of phenol - BPA Production Process