Chemistry · Grade 12

Active learning ideas

Reactions Involving Functional Groups

Explore the chemical transformations that create the scents in our foods and the fabrics in our clothes. This topic uncovers how the reactive sites on molecules, their functional groups, direct these powerful changes.

• Ontario Curriculum Expectations
• Ontario Curriculum: SCH4U, Strand B - Organic Chemistry, B3: Demonstrate an understanding of the structure, properties, and chemical behaviour of compounds within each class of organic compounds.

• 30–90 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Experiential Learning
• 90 min · Pairs

Making Scents: Ester Synthesis Lab

Students synthesize a specific ester, like methyl salicylate (wintergreen) or isoamyl acetate (banana), by reacting a carboxylic acid with an alcohol using an acid catalyst. They will observe the characteristic odour and learn about reaction conditions and purification.

Compare the products of oxidizing a primary, secondary, and tertiary alcohol.

Facilitation Tip

Emphasize safety precautions, especially when handling concentrated acids and heating flammable alcohols in a water bath.

What to look for

Think-Pair-Share: Pose a problem, such as 'Predict the product of oxidizing 2-propanol.' Students think individually, discuss with a partner, and then share their proposed product and reasoning with the class.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 02

• Experiential Learning
• 30 min · Small Groups

Alcohol Oxidation Race

In a well-ventilated area or fume hood, students add a few drops of acidified potassium permanganate solution to test tubes containing a primary, a secondary, and a tertiary alcohol. They observe the relative rates and results of the colour change, visually differentiating the reactivity of each alcohol class.

Explain the reaction mechanism for the acid-catalyzed formation of an ester from a carboxylic acid and an alcohol.

Facilitation Tip

Use this as a discovery activity before formally teaching the theory to promote inquiry-based learning.

What to look for

Reaction Quiz: A section on a unit test where students must complete chemical equations, including predicting products, identifying necessary reagents, and naming all organic compounds for oxidation, esterification, and hydrolysis reactions.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 03

• Experiential Learning
• 30 min · Small Groups

Esterification Mechanism Puzzle

Students work in groups with cut-out cards representing molecules, intermediates, and curved arrows to correctly sequence the step-by-step mechanism for acid-catalyzed esterification. This hands-on approach helps demystify the complex process of electron movement.

Justify the conditions required for the saponification of an ester.

Facilitation Tip

Circulate and ask guiding questions about protonation and which atom is the strongest nucleophile to help groups that are stuck.

What to look for

Mechanism Analysis: Provide students with a flawed reaction mechanism for esterification and ask them to identify and correct the errors in electron flow, proton transfers, or intermediate structures.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

A few notes on teaching this unit

Start by reviewing the structures of alcohols, carboxylic acids, and esters using molecular models to highlight the reactive sites. When introducing mechanisms, use a 'follow the electrons' approach, explicitly modelling how to draw curved arrows from a nucleophile to an electrophile. Use analogies, like comparing saponification to 'cutting' an ester with 'chemical scissors' (hydroxide ions), to make the processes more intuitive.

Students will be able to predict the products of key organic reactions and explain the step-by-step mechanisms that drive the conversion of one functional group into another.

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Watch Out for These Misconceptions

• In esterification, the water molecule is formed from the -OH of the alcohol and the -H of the carboxylic acid.

  Isotopic labelling studies have proven that the water molecule is formed from the entire -OH group of the carboxylic acid and the -H from the alcohol's hydroxyl group. The oxygen from the alcohol becomes the oxygen atom in the ester's ether linkage.

• Oxidation in organic chemistry always means adding oxygen atoms.

  While adding oxygen is one form of oxidation, it is more broadly defined as an increase in the number of carbon-oxygen bonds or a decrease in the number of carbon-hydrogen bonds. For example, the oxidation of a primary alcohol to an aldehyde involves the loss of two hydrogen atoms.

• Saponification is simply the reverse reaction of esterification.

  Saponification (base-catalyzed hydrolysis) is an irreversible reaction, unlike acid-catalyzed esterification which is an equilibrium. The final step in saponification is an acid-base reaction forming a very stable carboxylate salt, which drives the reaction to completion.

• Tertiary alcohols can be oxidized just like primary and secondary alcohols.

  Tertiary alcohols are resistant to oxidation under normal conditions because the carbon atom bonded to the -OH group does not have any hydrogen atoms attached. Oxidation would require breaking a much stronger carbon-carbon bond, which requires very harsh conditions.

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Methods used in this brief

• Experiential Learning