Substitution reactions may occur by either of two mechanisms namely ${\mathrm{S}}_{\mathrm{N}}1$ or ${\mathrm{S}}_{\mathrm{N}}2$. Outline the meaning of the term ${\mathrm{S}}_{\mathrm{N}}1$.

Predict the mechanism $\left({\mathrm{S}}_{\mathrm{N}}1 \mathrm{or} {\mathrm{S}}_{\mathrm{N}}2\right)$ expected for the reaction of the following halogenoalkanes with aqueous $\mathrm{KOH}$.

• 1-chlorobutane to form butan-1-ol
• 2-chloro-2-methylpropane to form 2-methylpropan-2-ol.

Explain the mechanism of each of the following reactions using curly arrows to represent the movement of electron pairs.

• 1-chlorobutane to form butan-1-ol
• 2-chloro-2-methylpropane to form 2-methylpropan-2-ol.

There are several structural isomers with the molecular formula ${\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{Br}$.

Deduce the name of one of the isomers which can exist as enantiomers and draw three-dimensional representations of its two enantiomers.

${\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{Br}+\mathrm{NaOH}\to {\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{OH}+\mathrm{NaBr}$

The reaction with 1-bromopentane proceeds by an ${\mathrm{S}}_{\mathrm{N}}2$ mechanism. Describe this mechanism using structural formulas and curly arrows to represent the movement of electron pairs.

${\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{Br}+\mathrm{NaOH}\to {\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{OH}+\mathrm{NaBr}$

The reaction with 2-bromo-2-methylbutane proceeds by an ${\mathrm{S}}_{\mathrm{N}}1$ mechanism. Describe this mechanism using structural formulas and curly arrows to represent the movement of electron pairs.

Explain why 1-bromopentane reacts by an ${\mathrm{S}}_{\mathrm{N}}2$ mechanism whereas 2-bromo-2-methylbutane reacts by an ${\mathrm{S}}_{\mathrm{N}}1$ mechanism.

Explain whether the boiling point of 1-bromopentane will be higher, lower, or the same as that of 2-bromo-2- methylbutane.

${\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{Br}+\mathrm{NaOH}\to {\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{OH}+\mathrm{NaBr}$

The product ${\mathrm{C}}_5{\mathrm{H}}_{11}\mathrm{OH}$ formed from the reaction with 1-bromopentane is warmed with ethanoic acid in the presence of a few drops of concentrated sulphuric acid. State the name of the type of reaction taking place and the structural formula of the organic product.