Question

Carbon-carbon double bond length will be maximum in which of the following compounds?

• A. $C{H}_3-CH=C{H}_2$
• B. $C{H}_3-CH=CH-C{H}_3$
• C. $C{H}_3-\underset{C{H}_3}{\underset{|}{C}=}\underset{C{H}_3}{\underset{|}{C}-}C{H}_3$
• D. $C{H}_2=C{H}_2$

Answer 1

The correct option is C $C{H}_3-\underset{C{H}_3}{\underset{|}{C}=}\underset{C{H}_3}{\underset{|}{C}-}C{H}_3$

Due to hyperconjugation by methyl group the double bond is partially shared as shown. Therefore more no of hyperconjugation means more bond sharing and hence less double bond character and therefore longer bond. Therefore option $\left(C\right)$ is correct as it contains maximum hyperconjugation.