Question

1. why is HCl not a good choice as the acid to catalyze a dehydration reaction?

Answer 1

Answer:

1) HCl contains the Cl^- which is a good nucleophile

2) 2-methyl-2- heptanol > 2-heptanol > 1-heptanol

3) see image attached

Explanation:

If the dehydration of alcohols is carried out using HCl, the chloride ion which is a good nucleophile will attack the substrate to yield an undesirable product.

The dehydration of alcohols is an E1 reaction. Recall that the ease of E1 reaction increases in the order 3°> 2°> 1°. Hence, 2-methyl-2- heptanol forms a tertiary carbocation intermediate during dehydration and has the greatest ease of dehydration.

The three products formed during the dehydration of 3,3-dimethyl-2-butanol are shown in the image attached. Two out of the three are formed by rearrangement reactions.