Chapter 17, Problem 17.53P

Interpretation Introduction

(a)

Interpretation:

The complete mechanism that proceeds when the given species treated with triphenylphosphine followed by butyllithium is to be drawn.

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 reaction fovors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${\text{Ph}}_{\text{3}}\text{P}$ attacks on the carbon attached to the halide anion. The organic product accommodates the positive charge on the phosphorus atom due to the large size and its electronegativity. Finally, deprotonation carried 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.

Answer to Problem 17.53P

The complete mechanism of the given alkyl halide is treated with triphenylphosphine followed by butyllithium as shown below.

Explanation of Solution

The given alkyl halide is

The Wittig reagent is generated from the given alkyl halide and triphenylphosphine followed by butyllithium. Triphenylphosphine, ${\text{Ph}}_{\text{3}}\text{P}$ is a very good nucleophile, so it favors ${\text{S}}_{\text{N}}\text{2}$ reaction. Firstly, nucleophile treated with the alkyl halide and ${\text{Br}}^{\text{-}}$ departs from the substrate in the same step. The product accommodates the positive charge on the P atom.

Lastly, the product obtained from the first step is treated with butyllithium to form Wittig reagent. ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{Li}$, strong base abstracts the proton from a Carbon atom. The carbon atom that is deprotonated possesses the negative charge and it is stabilized by the positive charge on P.

The complete mechanism of the given alkyl halide is treated with triphenylphosphine followed by butyllithium as shown below.

Conclusion

The complete mechanism for the given species treated with triphenylphosphine followed by butyllithium is drawn.

Interpretation Introduction

(b)

Interpretation:

The complete mechanism that proceeds when the given species treated with triphenylphosphine followed by butyllithium is to be drawn.

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 reaction fovors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${\text{Ph}}_{\text{3}}\text{P}$ attacks on the carbon attached to the halide anion. The organic product accommodates the positive charge on the phosphorus atom due to the large size and its electronegativity. Finally, deprotonation carried 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.

Answer to Problem 17.53P

The complete mechanism of the given alkyl halide is treated with triphenylphosphine followed by butyllithium as shown below.

Explanation of Solution

The given alkyl halide is

The Wittig reagent is generated from the given alkyl halide and triphenylphosphine followed by butyllithium. Triphenylphosphine, ${\text{Ph}}_{\text{3}}\text{P}$ is a very good nucleophile, so it favors ${\text{S}}_{\text{N}}\text{2}$ reaction. Firstly, nucleophile treated with alkyl halide and the leaving group, ${\text{Br}}^{\text{-}}$ departs from the substrate in the same step. The product accommodates the positive charge on the P atom.

Lastly, the product obtained from the first step is treated with butyllithium to form Wittig reagent. ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{Li}$, strong base abstracts the proton from a Carbon atom. The carbon atom that is deprotonated possesses the negative charge and it is stabilized by the positive charge on P.

The complete mechanism of the given alkyl halide is treated with triphenylphosphine followed by butyllithium as shown below.

Conclusion

The complete mechanism for the given species treated with triphenylphosphine followed by butyllithium is drawn.

Interpretation Introduction

(c)

Interpretation:

The complete mechanism that proceeds when the given species treated with triphenylphosphine followed by butyllithium is to be drawn.

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 reaction fovors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${\text{Ph}}_{\text{3}}\text{P}$ attacks on the carbon attached to the halide anion. The organic product accommodates the positive charge on the phosphorus atom due to the large size and its electronegativity. Finally, deprotonation carried 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.

Answer to Problem 17.53P

The complete mechanism of the given alkyl halide is treated with triphenylphosphine followed by butyllithium as shown below.

Explanation of Solution

The given alkyl halide is

The Wittig reagent is generated from the given alkyl halide and triphenylphosphine followed by butyllithium. Triphenylphosphine, ${\text{Ph}}_{\text{3}}\text{P}$ is a very good nucleophile, so it favors ${\text{S}}_{\text{N}}\text{2}$ reaction. Firstly, nucleophile treated with the alkyl halide and the leaving group, ${\text{Cl}}^{\text{-}}$ departs from the substrate in the same step. The product accommodates the positive charge on the P atom.

After that, the product obtained from the first step is treated with butyllithium to form Wittig reagent. ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{Li}$, strong base abstracts the proton from a Carbon atom. The carbon atom that is deprotonated possesses the negative charge and it is stabilized by the positive charge on P.

The complete mechanism of the given alkyl halide is treated with triphenylphosphine followed by butyllithium as shown below.

Conclusion

The complete mechanism for the given species treated with triphenylphosphine followed by butyllithium is drawn.