7. Substitution Reactions

When equivalent amounts of methyl bromide and sodium iodide are dissolved in methanol, the concentration of iodide ion quickly decreases and then slowly returns to its original concentration. Account for this observation.

Provide an arrow-pushing mechanism that rationalizes the outcome of the reaction shown.

Optically active 2-bromobutane undergoes racemization on treatment with a solution of KBr. Propose a mechanism for this racemization.

Provide a mechanism for the following S_N1 reactions that feature a rearrangement.

(b)

Suggest a mechanism for the following substitution reactions.

(c)

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (vii) HCl; (viii) HBr; If no reaction occurs, write 'no reaction.'

(o)

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions:(vii) HCl; (viii) HBr If no reaction occurs, write 'no reaction.'

(k)

What stereoisomers does the following reaction form?

When tert-butyl bromide is heated with an equal amount of ethanol in an inert solvent, one of the products is ethyl tert-butyl ether.

a. What happens to the reaction rate if the concentration of ethanol is doubled?

Explain the difference in reactivity between CH₃O⁺H₂ and CH₃OH in a nucleophilic substitution reaction. (The pK_a of H₃O⁺ is −1.7.)