Chapter 8, Problem 15E

(a)

Interpretation Introduction

Interpretation: Mechanism for the first synthetic step of oxymercuration-demercuration reaction shown below should be drawn.

Concept introduction: Alkenes are regarded as electron-rich and often undergo addition reaction in the presence of electrophilic halo acids or mercuric acetate in the presence of THF solvent. The intermediate formed in former is a carbocation and finally nucleophilic part of halo acid or mercuric acetate attacks in a rapid step to give addition product.

  

(b)

Interpretation Introduction

Interpretation: A Lewis structure of ${\text{NaBH}}_{\text{4}}$ should be drawn.

Concept introduction: Lewis structures depict covalent bonds and describe valence electrons are present in the molecule. The sequence that leads to the Lewis structure of the molecule is as follows:

• Identify the central atom and arrange various other atoms around it. This atom so chosen is the least electronegative one.

• Estimate the total valence electrons.

• First, place a single bond between each pair.

• The remaining electrons can be allocated as lone pairs to satisfy the octet rule for each atom.

(c)

Interpretation Introduction

Interpretation: Particular characteristics of oxymercuration reaction shown below should be explained.

  

Concept introduction: Oxymercuration takes place in the presence of $\text{Hg}{\left(\text{OAc}\right)}_{\text{2}}$ and THF solvent. The overall addition of nucleophilic water ( $\text{OH}$ and $\text{H}$ ) occurs in accordance with Markovnikov’s Rule. Rule suggests that the negative part of nucleophiles must go to the carbon that has more alkyl substituents or less $\text{H}$ atoms. No carbocation rearrangement is involved.

(d)

Interpretation Introduction

Interpretation: Mechanism for acid-catalyzed hydration of below alkene substrate should be drawn.

  

Concept introduction: Acid-catalyzed hydration is the electrophilic addition of water. The reactive species that act as a catalyst are ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$

.In the second stage water, itself acts as a nucleophile and abstracts a proton to hydration product. The carbocation rearrangement can also be found in such reactions.