Question

1. Rank the following alcohols in order of ease of dehydration and explain your reason(s) for the ranking: 1-heptanol; 2-heptanol; 2-methyl-2-heptanol.

2. Draw three possible products from the dehydration of 3,3-dimethyl-2-butanol. Realize two of the products will come from a rearrangement.

3. Why is HCl not a good choice as the acid to catalyze a dehydration reaction?

Answer 1

3) in acid catalised dehydration first alcohols are protonated to form -H2O+ . in further step this -H2O+ will be eliminated and forms carbocation . it is more important step in dehydration process.

H2SO4 forms HSO4- after protonation . HSO4- can eliminate -H2O+ ion forms carbocation . but

in case of HCl . first it forms -H2O+ on alcohol. later it is not eliminated by Cl-. that means carbo cation will not form. if we use HCl.

so HCl is not suitable for acid catalysed dehydration.