The formation of 2-butene as a major product by dehydration of 2-butanol is in accordance with
Answers
The dehydration of butan-2-ol
The first two stages
There is nothing new at all in these stages.
In the first stage, the alcohol is protonated by picking up a hydrogen ion from the sulphuric acid.
In the second stage, the positive ion then sheds a water molecule and produces a carbocation.
The complication arises in the next step. When the carbocation loses a hydrogen ion, where is it going to come from?
Where does the hydrogen get removed from?
So that a double bond can form, it will have to come from one of the carbons next door to the one with the positive charge.
If a hydrogen ion is lost from the CH3 group
But-1-ene is formed.
If a hydrogen ion is lost from the CH2 group
This time the product is but-2-ene, CH3CH=CHCH3.
In fact the situation is even more complicated than it looks, because but-2-ene exhibits geometric isomerism. You get a mixture of two isomers formed - cis-but-2-ene and trans-but-2-ene.
Cis-but-2-ene is also known as (Z)-but-2-ene; trans-but-2-ene is also known as (E)-but-2-ene. For an explanation of the two ways of naming these two compounds, follow the link in the box below.
The overall result
Dehydration of butan-2-ol leads to a mixture containing:
but-1-ene
cis-but-2-ene (also known as (Z)-but-2-ene)
trans-but-2-ene (also known as (E)-but-2-ene