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Reactivity 3. What are the mechanisms of chemical change?

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  1. 3.1 Proton transfer reactions

    1. • Acid = proton donor • Base = proton acceptor • Deduce acid and base in a reaction; distinguish base and alkali

    2. • Differ by one proton • Deduce conjugate acid/base formulas

    3. • Can act as both acid and base • Write equations showing acid and base behaviour

    4. • pH = −log₁₀[H⁺] • [H⁺] = 10⁻ᵖᴴ • Calculate pH and [H+]; include universal indicator and pH probe use

    5. • Kw = [H⁺][OH⁻] • Acidic: [H⁺] > [OH⁻] • Neutral: [H⁺] = [OH⁻] • Basic: [H⁺] < [OH⁻] • Recognize acidic, neutral, and basic solutions from [H+] and [OH-]

    6. • Differ in extent of ionization • Equilibrium favors weaker conjugate • Distinguish strong/weak from concentrated/dilute

    7. • Acid + metal oxide/hydroxide/carbonate/hydrogencarbonate • Formulate equations and identify parent acids/bases of salts

    8. • Strong acid-strong base titrations • Characteristic shapes • Sketch and interpret intercept and equivalence point for monoprotic titrations

  2. 3.2 Electron transfer reactions

    1. 3.2.1Oxidation and reduction

      • Electron transfer, oxidation state change • Oxygen gain/loss, hydrogen loss/gain • Oxidizing/reducing agents • Deduce oxidation states and identify oxidized/reduced species

    2. 3.2.2Half-equations

      • Separate oxidation and reduction • Show electron loss/gain • Deduce redox half-equations and equations in acidic or neutral solutions

    3. 3.2.3Periodic trends in redox

      • Metals: ease of oxidation • Halogens: ease of reduction • Metal displacement reactions • Predict metal oxidation and halogen reduction using supplied data

    4. 3.2.4Acids with reactive metals

      • Release H₂ gas • Deduce equations for reactive metals with dilute acids

    5. 3.2.5Electrodes in electrochemical cells

      • Oxidation at anode • Reduction at cathode • Signs/polarities in voltaic vs. electrolytic cells • Identify anode/cathode from electrode reactions

    6. 3.2.6Primary (voltaic) cells

      • Spontaneous redox → electrical energy • Electron flow: anode → cathode (external circuit) • Ion movement across salt bridge • Include metal/metal ion half-cells, circuit, and salt bridge

    7. 3.2.7Secondary (rechargeable) cells

      • Redox reactions reversible with electrical energy • Deduce charging reactions from discharge reactions and compare cell types

    8. 3.2.8Electrolytic cells

      • Electrical energy → chemical energy • Non-spontaneous reactions • Electrolysis of molten salts • Explain current conduction and deduce molten salt electrolysis products

    9. 3.2.9Oxidation of organic functional groups

      • Primary alcohols → aldehydes → carboxylic acids • Secondary alcohols → ketones • Include distillation/reflux setup and that tertiary alcohols are not oxidized similarly

    10. 3.2.10Reduction of organic functional groups

      • Carboxylic acids → aldehydes → primary alcohols • Ketones → secondary alcohols • Include hydride ion role; specific reducing agents and mechanisms are not assessed

    11. 3.2.11Reduction of unsaturated compounds

      • Addition of H₂ lowers unsaturation • Alkenes + H₂, alkynes + H₂ • Deduce hydrogenation products of alkenes and alkynes

  3. 3.3 Electron sharing reactions (Radicals)

    1. • Molecular entity with unpaired electron • Highly reactive • Recognize radical notation and high reactivity

    2. • Produces radicals • Halogens with UV light/heat (initiation step) • Use single-barbed arrows for single-electron movement

    3. • Alkanes + halogens • Propagation and termination steps • Mixture of products • Write initiation, propagation, and termination equations

  4. 3.4 Electron-pair sharing reactions

    1. • Donate electron pair to electrophile • Recognize nucleophiles as electron-rich species

    2. • Nucleophile donates pair, forms new bond • Another bond breaks, leaving group departs • Deduce substitution products from nucleophile and leaving group

    3. • Both electrons stay with one fragment • Forms ions • Use curly arrows to show electron-pair movement

    4. • Accept electron pair from nucleophile • Recognize electrophiles as electron-deficient species

    5. • High electron density at C=C bond • Reactions: + H₂O, + halogens, + hydrogen halides • Deduce alkene addition equations; SL mechanisms are not assessed

    6. • Lewis acid = electron-pair acceptor • Lewis base = electron-pair donor • Classify nucleophiles/electrophiles using Lewis acid-base theory

    7. • Lewis base + Lewis acid • Nucleophiles = Lewis bases • Electrophiles = Lewis acids • Explain coordination bond formation with electron-pair donation

    8. • Ligands donate electron pairs to transition metal cations • Identify ligands and central transition metal cations in complex ions