Question

For the following list of hydrocarbons, rank the hydrocarbons in strength from weakest acid to strongest acid. CH3CH2CHzCH3, CH3CH2C CH, CH3CH2CH-CH2 Weakest Strongest CH, CH2C CH CH CH,CH-CH2

Answer 1

A hydrogen tends to be more acidic when it is attached to a more electronegative atom. The given compounds are all alike except for the hybridization of one of the carbon atoms.

The alkanes have sp³ hybridization, alkenes have sp² hybridization and the alkanes have sp hybridization. We know that, sp hybridized carbons are more electronegative than sp² and sp³ hybridized carbons.

This is because of the difference in electronegativity is that, p orbitals are further away from the nucleus than s orbitals. So the more p orbitals contribution you have to the hybrid orbital, the less electronegative the hybrid orbital is. sp orbitals have the most "s" character (50%) while sp³ orbitals having the least.

The electronegativity order is :

sp>sp²>sp³

Hence, the acidic nature of the given compounds is :

Alkynes >Alkenes>Alkanes

The answer is :

1 butyne > 1 butene > Butane