Organic Reactions In Action

Overview

Students connect familiar organic compounds to reaction patterns and use structural or condensed formulae to predict products. The lesson builds on prior learning about bonding, homologous series, naming organic compounds and identifying functional groups, while developing the refreshed curriculum capabilities of using evidence, communicating scientific ideas and participating safely in collaborative learning.

Learning intentions

Students will:

• identify homologous series and functional groups in organic compounds
• describe combustion, oxidation, substitution, addition, esterification and hydrolysis
• write balanced equations using structural or condensed formulae
• distinguish observations, reagents and conditions, products, and reaction type
• use evidence and chemical reasoning to predict and check reactions

Success criteria

• I can identify the functional group and homologous series of a compound.
• I can write a balanced equation and include appropriate reagents or conditions.
• I can label the observation, reactants, products and reaction type.
• I can explain why a reaction occurs using bonding and functional-group ideas.

Curriculum links

• Senior secondary Science: understanding organic compounds, chemical reactions, representations and evidence-based explanations.
• Nature of Science: investigating, interpreting representations, communicating explanations and evaluating evidence.
• Science capabilities: use evidence, critique evidence, interpret data, and communicate in scientific language.
• Relevant learning connects with investigating practical chemical reactions and explaining organic production processes.

Prior knowledge: Students should know covalent bonding, molecular formulae, balancing equations, naming alkanes, alkenes and alcohols, and the meaning of saturated and unsaturated. Briefly revisit these concepts if needed.

Key vocabulary: homologous series, functional group, alkane, alkene, alcohol, carboxylic acid, ester, combustion, oxidation, substitution, addition, esterification, hydrolysis, reagent, catalyst, reflux, observation, product.

Lesson structure (60 minutes)

1. 0–5 min · Hook and retrieval. Display a fuel flame, ripe fruit and scented ester image in the hook and retrieval slides; ask, “What do these have in common chemically?” Students individually name any organic compounds or reactions they recognise, then compare answers.

2. 5–17 min · Explicit teaching: patterns and reaction language. Use the homologous series and reaction vocabulary slides to explain that a homologous series has the same functional group, similar chemical reactions and a regular change between members. Define functional groups: C=C in alkenes, –OH in alcohols, –COOH in carboxylic acids and –COO– in esters. Students annotate a four-column table: reaction type, reagents/conditions, observation, products.

Emphasise that an observation is evidence such as fizzing, heat or a colour change; it is not the equation or product. Reagents and conditions cause the reaction, while products are the new substances formed.

3. 17–30 min · Worked examples. Model each example on the worked-equation slides, thinking aloud and requiring students to predict the next step.

• Combustion: identify carbon and hydrogen, form CO₂ and H₂O, then balance. CH₄ + 2O₂ → CO₂ + 2H₂O Observation: blue flame, heat and light. Reagent/condition: oxygen and ignition. Product: carbon dioxide and water. Type: combustion.

• Addition: locate the C=C bond, break the π bond and add one H–Br across it. CH₂=CH₂ + HBr → CH₃CH₂Br Observation: bromine water would decolourise if bromine were used instead. Reagent: HBr; condition: no special catalyst required at this level. Product: bromoethane. Type: addition. Stress that the carbon skeleton is not lost.

• Esterification: combine an alcohol and carboxylic acid, remove H₂O and name the ester from the two reactants. CH₃CH₂OH + CH₃COOH ⇌ CH₃COOCH₂CH₃ + H₂O Reagents/conditions: concentrated sulfuric acid catalyst and gentle heating. Observation: fruity smell, using wafting only. Products: ethyl ethanoate and water. Type: esterification and condensation.

Briefly show oxidation and hydrolysis: CH₃CH₂OH + [O] → CH₃COOH + H₂O (ethanol oxidised, acidified dichromate, heat; orange to green). CH₃COOCH₂CH₃ + H₂O ⇌ CH₃COOH + CH₃CH₂OH (acidic hydrolysis, heat). Explain substitution with a halogenoalkane: CH₃CH₂Br + OH⁻ → CH₃CH₂OH + Br⁻. A hydrogen or halogen is replaced by another group.

4. 30–40 min · Guided practice with fading prompts. Students complete three reactions on the board or in books. Begin with prompts: “What functional group is present?”, “Which bond changes?”, “What atoms must balance?” Gradually remove prompts and ask pairs to classify each reaction and add observations and conditions. Pause for mini-whiteboard checks. Correct the misconception that “oxidation always means adding oxygen”: explain that oxidation may also involve loss of hydrogen or electrons, although oxygen is used in this course’s alcohol examples.

5. 40–53 min · Independent worksheet practice. Distribute selected sections of the Organic Chemistry Reactions Worksheet. Students complete the reaction-identification, equation-writing and conditions questions, including at least one combustion, addition, oxidation, substitution, esterification or hydrolysis example. Students must label observation, reagents/conditions, products and reaction type. Circulate and confer: ask students to explain each decision rather than supplying products.

6. 53–58 min · Peer and self-check. Use the checking and correction slides to reveal equations and conditions one at a time. Students check in a different colour, identify one error pattern and correct it. Remind students that reversible reactions need ⇌, catalysts are written above the arrow, and state symbols are included only when known and useful.

7. 58–60 min · Exit ticket and close. Students answer: “For ethanol + ethanoic acid, identify the reaction type, write the equation, state one condition, and distinguish one observation from one product.” Collect responses and preview that the next lesson will use reaction pathways to synthesise organic compounds.

Resources

• the complete organic reactions teaching deck
• the Organic Chemistry Reactions Worksheet
• Mini-whiteboards, pens and erasers
• Student exercise books and periodic tables
• Molecular model kits or displayed structural formulae
• Safety glasses for any teacher demonstration
• Optional teacher demonstration materials: ethanol, acidified dichromate and a fume cupboard

Assessment

• Check retrieval responses, mini-whiteboards and explanations during guided practice.
• Mark selected worksheet questions for correct formulae, balancing, reaction classification and conditions.
• Use the exit ticket to identify whether students confuse observations with products or omit conditions; reteach these points next lesson.

Differentiation

• Support: provide a reaction-word bank, partially completed structural formulae, colour-coded functional groups and the prompts “identify, change, balance, classify”. Pair students strategically and allow oral rehearsal before writing.
• EAL and learning support: use a visual reaction template with separate boxes for observation, reagents/conditions, products and reaction type; explicitly model pronunciation and display vocabulary throughout.
• Extension: students construct a two-step pathway from an alkene to an ester, justify the reagents and conditions, and explain how hydrolysis reverses esterification.
• Address misconceptions directly: addition does not produce water; ester names do not simply repeat both reactant names; catalysts change reaction rate, not the final equilibrium position; balancing changes coefficients, never subscripts.

Safety: No student handling of chemicals is required. If demonstrating oxidation, the teacher uses small quantities, safety glasses, gloves and a fume cupboard, follows school chemical-management procedures, and avoids smelling chemicals directly. Demonstrate wafting only and discuss safe disposal. Do not use an open flame near ethanol.