IB Chemistry SL 3.4.2 Nucleophilic Substitution Questions

Use real SL exam questions to identify the attack site, predict substitution products and show hydroxide or cyanide electron-pair movement.

Exam points

Identify the electron-deficient carbon bonded to the leaving group as the attack site for a nucleophile.
Deduce the substitution product by replacing the leaving group with the nucleophile while preserving the carbon skeleton.
Show new-bond formation and leaving-group departure with correctly sourced curly arrows and electron-pair movement.

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Study 3.4.2—Nucleophilic substitution conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 2]

Chlorine undergoes many reactions.

(a)

Predict, giving a reason, whether ethane or chloroethane is more reactive.

[ 1 ]

chloroethane AND C-Cl bond is weaker/ $324 \mathrm{~kJ} \mathrm{~mol}^{-1}$ than C-H bond $/ 414 \mathrm{~kJ} \mathrm{~mol}^{-1}$

OR

chloroethane AND contains a polar bond

Marking guidance:

Accept "chloroethane AND polar".

(b)

Write the equation for the reaction of chloroethane with a dilute aqueous solution of sodium hydroxide.

[ 1 ]

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{l})+\mathrm{OH}^{-}(\mathrm{aq}) \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})$

OR
$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{l})+\mathrm{NaOH}(\mathrm{aq}) \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq})$

Marking guidance:

Accept use of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$ and $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} / \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ in the equation.

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IB Chemistry SL 3.4.2 Nucleophilic Substitution Questions question 1

Question (a)

Question (b)