How does 2 butene form when 1butanol is dehydrated with conc.H2SO4? Why 1 butene is not formed?

Question

Answer

H2O will remove

Answer

Dehydration of 1-butanol with conc. H2SO4

When 1-butanol is dehydrated with conc. H2SO4, it undergoes elimination reaction to form two isomers of butene - 1-butene and 2-butene.

Formation of 2-butene

2-butene is the major product formed in the reaction due to the following reasons:

The reaction proceeds via the E1 mechanism, which involves the formation of a carbocation intermediate.

The carbocation intermediate formed during the reaction is more stable in the case of 2-butene due to the presence of a tertiary carbon atom, which can stabilize the positive charge through hyperconjugation.

In the case of 1-butene, the carbocation intermediate formed would be less stable due to the absence of a tertiary carbon atom, leading to a lower yield of 1-butene.

Why 1-butene is not formed?

The formation of 1-butene is disfavored due to the following reasons:

The carbocation intermediate formed during the reaction is less stable in the case of 1-butene due to the absence of a tertiary carbon atom, leading to a lower yield of 1-butene.

The reaction conditions (i.e., conc. H2SO4) promote the formation of the more stable 2-butene isomer.

Therefore, the dehydration of 1-butanol with conc. H2SO4 primarily leads to the formation of 2-butene as the major product.