The presence of a nitrogen in the ring or groups α to the ring like a carbonyl group ( C =O ) , an imine group ( C = N ) , a vinyl group ( C = C ) , or an anion will also suffice as a source of pi orbitals to maintain conjugation .
Also , pi orbitals needed for conjugation can come from substituent groups α to the ring like : a carbonyl group ( C =O ) , an imine group ( C = N ) , a vinyl group ( C = C ) , or an anion .