Chapter 17, Problem 17.54P

Interpretation Introduction

(a)

Interpretation:

The synthesis of the given Witting reagent from an alkyl halide is to be shown.

Concept introduction:

Wittig reagents can be generated from alkyl halides. The alkyl halide is first reacted with triphenylphosphine and the product of that reaction is treated with a strong base. In the first step, the reaction favors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${\text{Ph}}_{\text{3}}\text{P}$ attacks on the carbon attached to the leaving group (halide anion). The organic product accommodates the positive charge on the phosphorus atom due to the large size and its electronegativity. Finally, deprotonation is carried out by butyllithium. It is a very strong base which is necessary because deprotonation takes place at a carbon atom. However, deprotonation is facilitated because the negatively charged carbon is stabilized by the adjacent positive charge on the P atom.

Interpretation Introduction

(b)

Interpretation:

The synthesis of the given Witting reagent from an alkyl halide is to be shown.

Concept introduction:

Wittig reagents can be generated from alkyl halides. The alkyl halide is first reacted with triphenylphosphine and the product of that reaction is treated with a strong base. In the first step, the reaction favors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${\text{Ph}}_{\text{3}}\text{P}$ attacks the carbon attached to the leaving group (halide anion). The organic product accommodates the positive charge on the phosphorus atom due to the large size and its electronegativity. Finally, deprotonation is carried out by butyllithium. It is a very strong base and which is necessary because deprotonation takes place at a carbon atom. However, deprotonation is facilitated because negatively charged carbon is stabilized by the adjacent positive charge on the P atom.

Interpretation Introduction

(c)

Interpretation:

The synthesis of given Witting reagent from an alkyl halide is to be shown.

Concept introduction:

The Wittig reagents can be generated from alkyl halides. The alkyl halide is first reacted with triphenylphosphine and the product of that reaction is treated with a strong base. In the first step, the reaction favors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${\text{Ph}}_{\text{3}}\text{P}$ attacks on the carbon attached to the leaving group (halide anion). The organic product accommodates the positive charge on the phosphorus atom due to the large size and its electronegativity. Finally, deprotonation is carried out by butyllithium. It is a very strong base and which is necessary because deprotonation takes place at a carbon atom. However, deprotonation is facilitated because the negatively charged carbon is stabilized by the adjacent positive charge on the P atom.