Chapter 12, Problem 12.12P

Interpretation Introduction

(a)

Interpretation:

Complete and detailed mechanism of the given reaction is to be drawn and major product of the given reaction is to be identified.

Concept introduction:

Water can undergo the acid-catalyzed addition to an alkene producing alcohol. Electrophilic addition of ${\text{H}}^{\text{+}}$ produces the stable carbocation intermediate. Carbocation intermediate is capable of rearrangement via $\text{1, 2-alkyl shift}$ for more stability. In coordination step ${\text{H}}_{\text{2}}\text{O}$ attacks the carbocation which follows the Markovnikov addition. In last step proton transfer produces an uncharged alcohol.

Interpretation Introduction

(b)

Interpretation:

Complete and detailed mechanism of the given reaction is to be drawn and the major product is to be identified.

Concept introduction:

The method to add water across a double bond is oxymercuration-reduction also called as oxymercuration-demercuration reaction. In first step of electrophilic addition reaction between alkene and $\text{Hg}{\left(\text{OAc}\right)}_2$ results in a cyclic mercurinium ion intermediate. In second step water is act as nucleophile to open the three membered ring. In third step positively charged oxygen atom is deprotonated. In last step reducing agent sodium borohydride ${\text{(NaBH}}_{\text{4}}\text{)}$ replaces the Hg containing substituent with hydrogen atom.

The product of oxymercuration-reduction follows Markovnikov’s rule- that is the $\text{OH}$ group forms a bond to the carbon atom that can better stabilize a positive charge (the most substituted carbon atom in alkene). Rearrangement does not take place with oxymercuration-reduction.