7. Substitution Reactions

Why does tert-butyl bromide not participate in $S_{N2}$ reactions?

Which of the following statements correctly describes both $SN1$ and $E1$ reactions of alkyl halides?

Which of the following best represents the major organic product formed when 2-bromo-2-methylpropane reacts with water in an $S{N}_1$ reaction?

Which of the following substrates will undergo substitution only through an $S_{\mathrm{N}}1$ mechanism?

Given the following SN1 reaction: $C_4{H}_9\mathrm{Br}$ (tert-butyl bromide) reacts with $H_{2}O$, what are the major organic products formed?

Rank the following alkyl halides from most reactive to least reactive in an S_N1 reaction:

2-bromo-2-methylpentane, 2-chloro-2-methylpentane, 3-chloropentane, and 2-iodo-2-methylpentane.

Which of the following alkyl halides would undergo an $S_{\mathrm{N}}1$ reaction the fastest?

Rank the following alkyl halides in order of increasing reactivity in an $S{N}_1$ reaction: $\mathrm{CH}{3}_{\mathrm{Br}}$, $\mathrm{CH}{3}_{\mathrm{CH}}{2}_{\mathrm{Br}}$, $(\mathrm{CH}{3}_{)}2\mathrm{CHBr}$, $(\mathrm{CH}{3}_{)}3\mathrm{CBr}$.

A reluctant first-order substrate can be forced to ionize by adding some silver nitrate (one of the few soluble silver salts) to the reaction. Silver ion reacts with the halogen to form a silver halide (a highly exothermic reaction), generating the cation of the alkyl group.

Give mechanisms for the following silver-promoted rearrangements.

(b)

Propose a mechanism involving a hydride shift or an alkyl shift for each solvolysis reaction. Explain how each rearrangement forms a more stable intermediate.

Hint: Most rearrangements convert 2° (or incipient 1°) carbocations to 3° or resonance-stabilized carbocations.

(b)

Which of the following S_N1 reactions should proceed at a faster rate? Justify your answer on a reaction coordinate diagram.

When 3-bromo-1-methylcyclohexene undergoes solvolysis in hot ethanol, two products are formed. Propose a mechanism that accounts for both of these products.

Which reacts faster in an S_N1 reaction?

Propose a mechanism for each reaction, showing explicitly how the observed mixtures of products are formed.

(b) 2-methylbut-3-en-2-ol + HBr → 1-bromo-3-methylbut-2-ene + 3-bromo-3-methylbut-1-ene

The bromoalkanes shown below participate in S_N1 reactions with the relative rates shown. Explain this trend. relative rate: