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3.2.11—Reduction of unsaturated compounds

Syllabus
First assessment 2025
Objective
3.2.11
Level
HL

Hydrogenation of Alkenes and Alkynes

Hydrogenation adds H2 across π bonds. Continue addition until the required saturated product is formed; nickel, palladium or platinum catalysts with heat or pressure are typical conditions.

Count π bonds to determine hydrogen demand: one mole of H₂ saturates one C=C, while full conversion of one C≡C to C–C needs two moles of H₂. Keep the carbon skeleton unchanged when drawing the product.

Deducing Hydrogenation Products

Assessment in practice

Representative question

Question 1

[Maximum number: 2]

State the reagent and conditions needed and draw the structural formula of the product.

Electron Transfer Reactions Summary

Retrieve the route: assign oxidation states, balance half-equations, predict displacement, label cells, trace electrons and ions, follow organic redox pathways, calculate potentials and choose electrolysis products.

Check electron loss/gain, anode/cathode versus polarity, spontaneous sign, salt-bridge direction, ions present, organic functional-group direction and object-cathode placement.