Question

Which of the following cycloalkanes involves maximum torsional strain?

• A. Cyclopropane
• B. Cyclobutane
• C. Cyclopentane
• D. Cyclohexane

Answer 1

The correct option is A

Cyclopropane

From the given compounds, all of them are cycloalkanes with the carbons supposedly having $s{p}^3$ hybridizations as per VSEPR. But because they are all cyclic, the bond angles at the ring carbons will not be exactly equal to ${109}^{\circ }$ ${28}^{\prime }$.

According to Baeyer’s strain theory, the amount of the strain is directly proportional to the angle of deviation. $Angleofdeviation,d$ = $\frac{1}{2}({109}^{\circ }$ 28'- valency angle). $‘d^{\prime }$ is maximum in case of cyclopropane, thus torsional strain is maximum in cyclopropane.