Chapter 6, Problem 48P

(a)

Interpretation Introduction

Interpretation: The species ${\text{HO}}^{-}$ , ${\text{CH}}_3{\text{CO}}_2{}^{-}$ and water should be ranked in the order of basicity, nucleophilicity, and leaving-group ability.

Concept introduction: ${\text{S}}_{\text{N}}2$ reactions are facile when the leaving group is good, nucleophile is sufficiently reactive and alkyl halide is a primary alkyl halide.

Leaving-group ability is determined by the capacity of leaving group to accommodate the negative charge as it is displaced from the alkyl halide. Among halogens, the iodides are best leaving groups followed by bromide chloride and fluoride. Besides halides, some sulphonates and sulphate that can easily delocalize the negative charge can also behave as good leaving group. These include tosylate, mesylate and triflate.

In general, the weak conjugate bases that are derived from strong acids are also good leaving groups. Table for leaving groups on the basis of strength of bases are as follows:

  

(b)

Interpretation Introduction

Interpretation: The species ${\text{I}}^{-}{\text{,Br}}^{-}{\text{,Cl}}^{-}{\text{,F}}^{-}$ should be ranked in the order of basicity, nucleophilicity, and leaving-group ability.

Concept introduction: ${\text{S}}_{\text{N}}2$ reactions are facile when the leaving group is good, nucleophile is sufficiently reactive and alkyl halide is a primary alkyl halide.

Leaving-group ability is determined by the capacity of leaving group to accommodate the negative charge as it is displaced from the alkyl halide. Among halogens, the iodides are best leaving groups followed by bromide chloride and fluoride. Besides halides, some sulphonates and sulphate that can easily delocalize the negative charge can also behave as good leaving group. These include tosylate, mesylate and triflate.

In general, the weak conjugate bases that are derived from strong acids are also good leaving groups. Table for leaving groups on the basis of strength of bases are as follows:

  

(c)

Interpretation Introduction

Interpretation: The species ${\text{H}}_2{\text{N,NH}}_{\text{3}}{\text{,H}}_2{\text{P}}^{-}$ should be ranked in the order of basicity, nucleophilicity, and leaving-group ability.

Concept introduction: ${\text{S}}_{\text{N}}2$ reactions are facile when the leaving group is good, nucleophile is sufficiently reactive and alkyl halide is a primary alkyl halide.

Leaving-group ability is determined by the capacity of leaving group to accommodate the negative charge as it is displaced from the alkyl halide. Among halogens the iodides are best leaving groups followed by bromide chloride and fluoride. Besides halides some sulphonates and sulphate that can easily delocalize the negative charge can also behave as good leaving group. These include tosylate, mesylate and triflate.

In general, the weak conjugate bases that are derived from strong acids are also good leaving groups. Table for leaving groups on the basis of strength of bases are as follows:

  

(d)

Interpretation Introduction

Interpretation: The species ${\text{OCN}}^{-}$ and ${\text{SCN}}^{-}$ should be ranked in the order of basicity, nucleophilicity, and leaving-group ability.

Concept introduction: ${\text{S}}_{\text{N}}2$ reactions are facile when the leaving group is good, nucleophile is sufficiently reactive and alkyl halide is a primary alkyl halide.

In general, the weak conjugate bases that are derived from strong acids are also good leaving groups. Table for leaving groups on the basis of strength of bases are as follows:

  

(e)

Interpretation Introduction

Interpretation: The species ${\text{HO}}^{-}{\text{,F}}^{-}{\text{,CH}}_3{\text{S}}^{-}$ should be ranked in the order of basicity, nucleophillicity, and leaving-group ability.

Concept introduction: ${\text{S}}_{\text{N}}2$ reactions are facile when the leaving group is good, nucleophile is sufficiently reactive and alkyl halide is a primary alkyl halide.

Leaving-group ability is determined by the capacity of leaving group to accommodate the negative charge as it is displaced from the alkyl halide. Among halogens, the iodides are best leaving groups followed by bromide chloride and fluoride. Besides halides, some sulphonates and sulphate that can easily delocalize the negative charge can also behave as good leaving group. These include tosylate, mesylate and triflate.

In general, the weak conjugate bases that are derived from strong acids are also good leaving groups.

Nucleophillicity varies directly with negative charge, and also for elements that lie far left and bottom of the periodic table. It also increases with polar aprotic solvents.

(f)

Interpretation Introduction

Interpretation: The species ${\text{H}}_2{\text{O, H}}_2{\text{S, NH}}_{\text{3}}$ should be ranked in the order of basicity, nucleophillicity, and leaving-group ability.

Concept introduction: ${\text{S}}_{\text{N}}2$ reactions are facile when the leaving group is good, nucleophile is sufficiently reactive and alkyl halide is a primary alkyl halide.

Leaving-group ability is determined by the capacity of leaving group to accommodate the negative charge as it is displaced from the alkyl halide. Among halogens, the iodides are best leaving groups followed by bromide chloride and fluoride. Besides halides, some sulphonates and sulphate that can easily delocalize the negative charge can also behave as good leaving group. These include tosylate, mesylate and triflate.

In general, the weak conjugate bases that are derived from strong acids are also good leaving groups. Table for leaving groups on the basis of strength of bases are as follows: