(b) For aromatic compounds following conditions should be satisfied (i) planarity (ii) complete delocalisation of π-electrons in the ring. (iii) presence of (4n+2)π-electrons in the ring, where n=0,1,2,... . This is called Huckel rule. e.g. n=0,2πe− n=1,6πe− n=2,10πe−