Lesson 4: Alcohols: Classification & Oxidation Reactions
Demonstrating understanding of organic chemical structure, properties, and reactions for NCEA Level 2 Chemistry.
🎯 Ngā Whāinga Akoranga | Learning Intentions
Primary, secondary, and tertiary alcohol structures; oxidation using acidified potassium permanganate (MnO4-/H+) and acidified potassium dichromate (Cr2O72-/H+); haloalkane elimination to alkenes.
Classify alcohols using structural formulas, observe and record colour changes in lab oxidations (purple to colorless, orange to green), and write oxidation pathways for primary and secondary alcohols.
🎥 Media Anchor & Pedagogical Scaffold
Alcohol Oxidation & Functional Group Conversion
Video Clip: GCSE Chemistry — Alcohols — structure, properties, classification, and reactions | Cognito (Runtime: 4m 07s).
🧠 1. Before Viewing (Activate & Predict)
How do breathalyzers detect ethanol in human breath using dichromate oxidation chemistry?
👁️ 2. During Viewing (Watch With a Job)
- Functional group: draw the hydroxyl (-OH) group and explain what makes it the characteristic group of all alcohols.
- Oxidation: the video shows what happens when a primary alcohol is oxidised. Write the type of product formed and name one reagent used for the oxidation.
- Fermentation vs synthesis: name TWO ways ethanol can be produced — state ONE advantage of each method.
🗣️ 3. After Viewing & Kaiako Move (Process & Apply)
Kaiako Move: Conduct the microscale alcohol oxidation practical. Discuss safety when handling concentrated acid catalysts.
Immediate Task: Complete Section 4 of your Organic Portfolio: Alcohol Classification & Oxidation Colour Change Diagnostic Matrix.
⚡ Whakaoho | Do Now: Organic Recall Challenge (10 mins)
Orange to green. Early breathalysers worked by blowing through a tube of acidified potassium dichromate. If the crystals turned from orange to green, the driver had been drinking.
Two minutes: dichromate is an oxidising agent and ethanol is an alcohol. Predict what the ethanol was turned into, and say what happened to the chromium to make it change colour. You have met both halves before — put them together.
📖 Activity 1: Core Reaction Mechanism & Structure Analysis (25 mins)
Classify first (10 min). You cannot predict an oxidation product until you know which kind of alcohol you have. Sort six alcohols into primary, secondary and tertiary by counting what is attached to the carbon bearing the –OH. Then predict each one's oxidation product. One will resist oxidation entirely — find it and explain what it is missing.
Two steps, not one (15 min). A primary alcohol oxidises twice. Draw ethanol → ethanal → ethanoic acid and label the reagent and condition driving each step. Then answer: if you wanted to stop at the aldehyde, what would you change about the apparatus, and why does distilling it off as it forms work?
📝 Activity 2: Level 2 Chemistry Portfolio Task & Merit/Excellence Scaffolding (20 mins)
Organic Portfolio — Section 4. Submit: (1) six alcohols classified with reasons; (2) oxidation equations with reagents, conditions and the observed colour change; (3) an explanation of why tertiary alcohols resist oxidation, written in terms of bonds rather than 'because they are tertiary'.
🏫 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.