Arrange benzene, n-hexane and ethyne in decreasing order of acidic behaviour. Also give reason for this behaviour.

Explanation

The hybridization state of carbon in these three compounds is

Since, s-electrons are closer to the nucleus , therefore , as the s-character of the orbital making the C-H bond increases, the electrons of C-H bond lie closer and closer to the carbon atom. In other words, the partial +ve charge on the H-atom increases and hence the acidic character increases as the s-character of the orbital increases. Thus, the acidic character decreases in the order : Ethyne gt Benzene gt Hexane