Chapter 7.2, Problem 7.2E

(a)

Interpretation Introduction

Interpretation: The value of $\Delta H°$ for overall reaction of $2\text{-fluoro-}2\text{-methylpropane}$ to $2\text{-fluoro-}2\text{-propanol}$ should be calculated.

Concept introduction:Thermodynamics is a study of energy transfers that can be done by either heat or work. The energy transferred through work involves force. When work is positive then system gains energy while when work is negative then system loses energy. Heat is not a state function and therefore change in enthalpy of reaction $\left(\Delta H{°}_{\text{rxn}}\right)$ has been introduced. The formula to calculate $\Delta H°$ from bond dissociation of reactants and products is as follows:

  $\Delta H°=\text{Sum of }DH°\text{ of bonds broken}-\text{Sum of }DH°\text{ of bonds formed}$

(b)

Interpretation Introduction

Interpretation: The mechanism using curved arrows should be indicated for below reactions.

  

Concept introduction:Unimolecuar substitution or ${\text{S}}_{\text{N}}1$ proceeds via a two-step mechanism. The first slow step that determines the rate is the removal of the leaving group from the substrate haloalkane and generates a carbocation. Since the rate is only governed by substrate alone and no other nucleophile or solvent it is termed as unimolecular substitution. The final step is the attack of the nucleophile on carbocation generated and the formation of racemic products.

A general ${\text{S}}_{\text{N}}1$ reaction mechanistic pathway is illustrated as follows:

  

(c)

Interpretation Introduction

Interpretation: The effect observed on the rate of methanolysis when the concentration of tertiary alkyl halide taken in (i) is doubled and diethyl ether is used to dilute methanol solvent should be determined.

  

Concept introduction:Unimolecuar substitution or ${\text{S}}_{\text{N}}1$ proceeds via a two-step mechanism. The first slow step that determines the rate is the removal of the leaving group from the substrate haloalkane and generates a carbocation. Since the rate is only governed by substrate alone and no other nucleophile or solvent it is termed as unimolecular substitution. The final step is the attack of the nucleophile on carbocation generated and the formation of racemic products. Rate of ${\text{S}}_{\text{N}}1$ follows first-order kinetics and is independent of solvent or nucleophile concentration as they are not involved in first rate-determining step.

A general ${\text{S}}_{\text{N}}1$ reaction mechanistic pathway is illustrated below: