Question

1)   The total number of π-bonds and closed rings in the molecular formula C₁₁H₁₂N₂O₂ is:

		A) 4
		B) 5
		C) 6
		D) 7

Answer 1

ANSWER D) 7

The total number of π-bonds and closed rings in a compound is given by the INDEX OF HYDROGEN DEFICIENCY (IDH) of the molecule

Calculation of IDH

The molecular formula of the compound =C₁₁H₁₂N₂O₂

The molecular formula of the corresponding alkane =C₁₁H₂₄

In the calculation of the number of H atoms in the compound , ignore O atoms and for each N atom present reduce the number of H atom by 1.(If X, a halogen atom is presentthen for each halogen atom increase the number of H atoms by 1)

In the compound C₁₁H₁₂N₂O₂ there are 2 N atoms and 12 H atoms. The net number of H atoms =12-2=10

IDH = (Number of H atoms in the corresponding alkane - The number(net) of H atoms in the compound)/2

      =(24 - 10)/2 =7

The total number of π-bonds and closed rings in the molecule = IDH = 7

ANSWER D) 7