Question

Calculate the number of rings present in C₁₈H₁₂.

Answer 1

Double bond equivalent formula = (C –\(\frac{1}{2}\) + \(\frac{1}{2}\)) Where C = no. of carbon atoms. H = no. of hydrogen and halogen atoms and N = no. of nitrogen atoms. So. in C₆H₆ Double bond equkalent = 18 – \(\frac{12}{2}\) + 0 + 1 = 18 – 6 + 1 = 13

One ring is equal to one double bond equivalent. 

∴ here four rings are there, four double bond equivalent arc used. So remaining, 13 – 4 = 9. 

nine double bonds are present in the ring. Hence, C₁₈H₁₂ contain four aromatic rings.