Question

The following cycloalkyne is too unstable to exist. Explain

Short answer

The linear geometry is distorted in the cyclopentyne and so the molecule is unstable.

Step-by-step solution

Stability of cyclic system with triple bonds

Alkynes are sp hybridized molecules. They have linear geometry and the bond angle is ${180}^0$. When the linear geometry is distorted, it results in angular strain and decreased stability. So when alkynes are present in cyclic structures they become unstable.

Stability of cyclopentyne

As from above figure we can observe that the triple bond is present in the ring. Triple bonded atom having linear hybridized orbitals. But due to cyclic systems linearity destroyed.

Hence cycloalkynes are less stable.