Question

Why are hydrogen of cyclopropane more acidic than propane?

Answer 1

The greater reactivity of cyclopropane derives from what we call bond-strain. When carbon atoms only have single bonds with neighboring atoms, the bonding electron pairs tend to get as far from each other as possible, leading to the well-known tetrahedral arrangement. The angle between the bonds is 109,5 degrees. In cyclopropane the three carbon ring forms an equilateral triangle, and the resulting bond angle will be 60 degrees: the bonds are heavily compressed, resulting in a lot of bond strain. It takes a lot less energy to break a tensed bond than a ‘relaxed’ bond.