Lesson 7: Organic Reaction Schemes & Multi-Step Synthesis
Demonstrating understanding of organic chemical structure, properties, and reactions for NCEA Level 2 Chemistry.
🎯 Ngā Whāinga Akoranga | Learning Intentions
Multi-step reaction conversion pathways linking alkanes, haloalkanes, alkenes, alcohols, carboxylic acids, and amines (substitution, addition, elimination, oxidation).
Construct multi-step synthesis flowcharts, identify required reagents/conditions (e.g., PCl5, SOCl2, KOH(alc), KOH(aq), H2SO4(conc), H+/Cr2O72-), and troubleshoot reaction schemes.
🎥 Media Anchor & Pedagogical Scaffold
Organic Reaction Schemes & Reagents Summary
Video Clip: Completing reaction schemes — NCEA Level 2 Organic Chemistry | Delene Holm (Runtime: 9m 08s).
🧠 1. Before Viewing (Activate & Predict)
How do synthetic organic chemists map out multi-step reaction pathways to create complex medicines from basic hydrocarbons?
👁️ 2. During Viewing (Watch With a Job)
- Steps in a scheme: using the video as a guide, what information must you identify at each arrow in a reaction scheme? (reactant, reagent, product — what else?)
- Work through: the video shows how to complete a 3-step reaction scheme. Describe in words the strategy: do you start at the beginning, end, or wherever you have the most information?
- Apply: draw a 2-step scheme converting ethene → ethanol → ethanoic acid. Label each arrow with the reagents and conditions required.
🗣️ 3. After Viewing & Kaiako Move (Process & Apply)
Kaiako Move: Provide the 'KOH Trap' memory mnemonic: KOH in Alcohol = Alkene (elimination); KOH in Aqua = Alcohol (substitution).
Immediate Task: Complete Section 7 of your Organic Portfolio: Master Reaction Pathways Map & Reagent Reconciler.
⚡ Whakaoho | Do Now: Organic Recall Challenge (10 mins)
You cannot get there in one step. Start with ethane. Finish with ethanoic acid. There is no single reagent that does it.
Two minutes: list every reaction type you have met so far — substitution, addition, elimination, oxidation. Then sketch any route from ethane to ethanoic acid, even a clumsy one. Do not worry about reagents yet; get the sequence of functional groups right first.
📖 Activity 1: Core Reaction Mechanism & Structure Analysis (25 mins)
Build the map (15 min). In pairs, draw a single diagram with alkane, haloalkane, alkene, alcohol, carboxylic acid and amine as nodes. Draw an arrow for every conversion you know and label it with reagent AND condition. Leave arrows you cannot justify off the map — a wrong arrow costs more than a missing one.
Solve three (10 min). Your kaiako will give three conversions. For each, give the shortest valid route with reagents and conditions at every step. Then answer the Excellence question: for one of them, explain why a shorter-looking route does not actually work.
📝 Activity 2: Level 2 Chemistry Portfolio Task & Merit/Excellence Scaffolding (20 mins)
Organic Portfolio — Section 7. Submit: (1) your completed conversion map, every arrow labelled with reagent and condition; (2) three multi-step syntheses written out in full; (3) one paragraph explaining a route you rejected and why.
🏫 Kaiako Planning & Pedagogy Notes
NCEA Level 2 Alignment: Direct preparation for NCEA Level 2 Chemistry (External) (Demonstrate understanding of the properties of selected organic compounds). Emphasise linking observations and reagents to molecular structure for Merit/Excellence grades.