Three small hydrocarbons are listed below in condensed structural form.
• Ethane: CH3–CH3
• Ethene: CH2═CH2
• Ethyne: HC≡CH
All atoms satisfy the octet rule and no resonance is involved.
(a) Describe the difference between a σ bond and a π bond in terms of the location and type of orbital overlap that produces each bond.
(b) For each hydrocarbon, determine the total number of σ bonds and the total number of π bonds present.
(c) For each hydrocarbon, explain whether free rotation about the carbon–carbon bond axis is possible. Support your answer by referring to the bonding identified in part (b).