3.4.1—Nucleophiles
- Syllabus
- First assessment 2025
- Objective
- 3.4.1
- Level
- SL
A nucleophile is an electron-rich species that donates an electron pair to an electron-deficient centre.
Look for an available electron pair: OH⁻ and CN⁻ use a negative charge and lone pair, while NH₃ uses a lone pair without being an anion. A curly arrow must start at that pair and point toward the atom where the new bond forms.
Representative question
Identify a nucleophile which could be used for this reaction.
OH−
Marking guidance:
Accept water / H2O
Accept "hydroxide"/ "sodium hydroxide / NaOH"
Retrieve the route: classify nucleophiles and electrophiles, show heterolysis, write substitution and addition mechanisms, map Lewis coordination, compare SN1/SN2, and restore aromaticity in benzene substitution.
Check electron-pair arrow origin and destination, leaving-group departure, intermediate identity, carbocation stability and the assessed mechanism boundary.