Ques. 1AIPMT 2015 (Cancelled)
Which of the following species contains equal number of σ- and π-bonds ?
- (CN)2
- CH2(CN)2
- HCO3-
- XeO4
Answer
(4) XeO4
Solution
A single bond = 1σ; a double bond = 1σ + 1π; a triple bond = 1σ + 2π.
(CN)2: N C-C N ⇒ 3σ, 4π
CH2(CN)2: N C-CH2-C N ⇒ 6σ, 4π
HCO3-: one C=O, two C–O, one O–H ⇒ 4σ, 1π
XeO4: Xe forms four Xe=O bonds (sp³, tetrahedral, four pπ–dπ bonds) ⇒ 4σ, 4π
∴ XeO4 has equal numbers of σ and π bonds.
Answer: (4)