Chapter 12, Problem 12.31P

Interpretation Introduction

(a)

Interpretation:

$\text{Dichloromethane}$ (${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$) can be treated with $\text{butyllithium}$, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2 }}\text{- Li}$ ($\text{Bu- Li}$), to make a carbene in situ, analogous to the way a carbene is generated from $\text{trichloromethane}$ (${\text{CHCl}}_{\text{3}}$) using ${\text{HO}}^{\text{-}}$. The mechanism for the generation of a carbene from ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ is to be shown.

Concept introduction:

A carbene is characterized by a C atom with two bonds and a lone pair of electrons. Even though the C atom is uncharged, carbenes are typically highly electrophilic due to the lack of an octet. Carbenes are sp2 hybridized. Carbenes can be made from strongly basic carbanion by following proton transfer and heterolysis steps.

Interpretation Introduction

(b)

Interpretation:

$\text{Dichloromethane}$ (${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$) can be treated with $\text{butyllithium}$, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2 }}\text{- Li}$ ($\text{Bu- Li}$) to make carbene in situ, analogous to the way a carbene is generated from $\text{trichloromethane}$ (${\text{CHCl}}_{\text{3}}$) using ${\text{HO}}^{\text{-}}$. The reason for using $\text{butyllithium}$ instead of ${\text{HO}}^{\text{-}}$ is to be explained.

Concept introduction:

For deprotonation of an acid, the base must be stronger if the acid is weaker. A base having positive charge and ${\text{sp}}^3$ hybridized carbon atom is stronger than the negatively charged ${\text{sp}}^3$ oxygen atom.

Interpretation Introduction

(c)

Interpretation:

All four products of the given reaction are to be drawn.

Concept introduction:

Carbenes are typically highly electrophilic due to the lack of an octet. Carbene reacts with alkene to generate the three-membered ring. The reaction produces a mixture of stereoisomers as alkene is planar, and the electrophile can be added to either face of the alkene. One stereoisomer is produced by the addition of the carbene to one face, and the second is produced by addition to the other face.