Lesson 7: Alcohol Reactions | Portfolio Course

Lesson at a Glance | He Tirohanga Whakamua

Do NowClassify propan-1-ol, propan-2-ol, 2-methylpropan-2-ol10 min

3 Key Alcohol ReactionsOxidation Reactions:

C r_{2} O_{7}^{2 -} / H^{+}

orange to green vs

M n O_{4}^{-} / H^{+}

purple to colourless · Lucas Reagent & Dehydration: Lucas test timing (

3^{\circ} < 1

min) & conc.

H_{2} S O_{4}

dehydration30 min

Portfolio EntryWrite Section 7: Alcohol Oxidation & Reaction Pathways10 min

Exit DrillPredict oxidation product of propan-1-ol vs 2-methylpropan-2-ol5 min

Ngā Whāinga Ako | Learning Intentions

Students will know

How Primary ( $1^{\circ}$ ), Secondary ( $2^{\circ}$ ), and Tertiary ( $3^{\circ}$ ) alcohols react differently under oxidation:
• $1^{\circ}$ alcohol $+ C r_{2} O_{7}^{2 -} / H^{+} \to$ Carboxylic Acid (Orange $\to$ Green $C r^{3 +}$ ).
• $2^{\circ}$ alcohol $+ C r_{2} O_{7}^{2 -} / H^{+} \to$ Ketone (Orange $\to$ Green).
• $3^{\circ}$ alcohol $+ C r_{2} O_{7}^{2 -} / H^{+} \to$ NO REACTION (Remains Orange).
How Lucas Reagent ( $Z n C l_{2} / conc. H C l$ ) distinguishes alcohol classes by rate of haloalkane cloudiness ( $3^{\circ}$ rapid $< 1$ min; $2^{\circ}$ 3–5 min; $1^{\circ}$ no reaction).
How Dehydration Elimination using conc. $H_{2} S O_{4}$ removes $H_{2} O$ from alcohols to form alkenes.

Students will demonstrate

By predicting observation changes for oxidation of propan-1-ol vs 2-methylpropan-2-ol.
By completing Section 7 of their Level 2 Organic Chemistry Mastery Portfolio.

Curriculum alignment

NZC (2007) · Science · Level 7 · Material World: “Investigate and measure the chemical and physical properties of a range of groups of substances, for example, acids and bases, oxidants and reductants, and selected organic and inorganic compounds.”

Do Now | Tīmatanga Whakaaro (10 min)

Dichromate Oxidation Prompt:

"When warm acidified potassium dichromate ( ${Cr}_{2} O_{7}^{2 -} / H^{+}$ ) is added to propan-1-ol, the orange solution turns bright green. When added to 2-methylpropan-2-ol, it stays orange. Why?"

Unpack: Propan-1-ol is a primary alcohol; it is oxidised to propanoic acid while reducing orange ${Cr}_{2} O_{7}^{2 -}$ to green ${Cr}^{3 +}$ . 2-methylpropan-2-ol is a tertiary alcohol; its carbon attached to $- O H$ has no hydrogen atom to lose, so it resists oxidation completely!

3 Key Alcohol Reactions (30 min)

🍊 1. Oxidation

$1^{\circ}$ Alcohol $\overset{{MnO}_{4}^{-} / H^{+}}{\to} Carboxylic Acid$ (Purple $\to$ Colourless ${Mn}^{2 +}$ ).
$1^{\circ}$ Alcohol $\overset{{Cr}_{2} O_{7}^{2 -} / H^{+}}{\to} Carboxylic Acid$ (Orange $\to$ Green ${Cr}^{3 +}$ ).

🧪 2. Substitution to Haloalkane

Alcohol $+ {PCl}_{5} / {SOCl}_{2} / conc. HCl \to Haloalkane$ .
Lucas Test: $3^{\circ}$ turns cloudy instantly; $2^{\circ}$ in 5 mins; $1^{\circ}$ no reaction.

💧 3. Dehydration Elimination

Alcohol $\overset{conc. H_{2} {SO}_{4}, heat}{\to} Alkene + H_{2} O$ .
Follows Saytzeff's Rule for unsymmetrical secondary alcohols.

🛑 Before any of this is run as a practical

This lesson names the most hazardous reagents in the unit. Acidified dichromate is toxic, is a known human carcinogen (chromium(VI) compounds are IARC Group 1) and has controlled disposal. Concentrated sulfuric acid is severely corrosive and releases a great deal of heat on contact with water — acid is added to water, never the reverse. Lucas reagent is zinc chloride in concentrated hydrochloric acid and is corrosive. PCl₅ and SOCl₂ react violently with water, releasing HCl gas. None of the portfolio work below requires handling any of them; a demonstration needs the school’s approved method, SDS information, PPE, fume extraction and direct kaiako supervision.

📁 Organic Chemistry Portfolio — Section 7: Alcohol Reactions & Lucas Test

Students open their Level 2 Chemistry Portfolio and complete Section 7:

Section 7 Requirements:

1. Oxidation Comparison Table: Products and observations for $1^{\circ}, 2^{\circ}, 3^{\circ}$ alcohols with ${Cr}_{2} O_{7}^{2 -} / H^{+}$ and ${MnO}_{4}^{-} / H^{+}$ .

2. Lucas Test Diagnostic Flowchart: Describe observations and timing for adding Lucas reagent ( $Z n C l_{2} / conc. H C l$ ) to 3 structural isomers of $C_{4} H_{9} OH$ .

3. Excellence Dehydration Mechanism: 1-paragraph explanation of conc. $H_{2} {SO}_{4}$ dehydration of butan-2-ol identifying major (but-2-ene) and minor (but-1-ene) products.

Answers & marking notes (kaiako) — screen only, does not print

Oxidation: primary → aldehyde → carboxylic acid; secondary → ketone; tertiary → NO reaction. Observations: Cr₂O₇²⁻/H⁺ orange → green; MnO₄⁻/H⁺ purple → colourless (both stay unchanged with a tertiary alcohol).
Lucas on C₄H₉OH isomers: 2-methylpropan-2-ol (tertiary) → cloudy immediately · butan-2-ol (secondary) → cloudy in ~5 min · butan-1-ol (primary) → no change at room temperature.

Exit Verification | Ka Mutu Hoki (5 min)

Exit Check:

"My Section 7 correctly identifies propanoic acid as the product of propan-1-ol oxidation and explains why 3° alcohols resist oxidation."

Teacher Planning & NCEA Alignment

NCEA Level 2 Chemistry Alignment (4 Credits External):

Alcohol Reactions: Predict reagents, conditions, colour changes, and products for oxidation, substitution, and dehydration reactions.

Enrichment — beyond the assessed scope of this standard:

Lucas Test: Distinguishing primary, secondary and tertiary alcohols by reaction rate with Lucas reagent is useful chemistry, but it sits outside what this standard assesses. Teach it as extension, and check your current assessment specification before students rely on it in an assessed answer.

Vocabulary: Primary alcohol, secondary alcohol, tertiary alcohol, oxidation, dichromate ( ${Cr}_{2} O_{7}^{2 -}$ ), permanganate ( ${MnO}_{4}^{-}$ ), Lucas reagent, dehydration, conc. $H_{2} {SO}_{4}$ .

Other teaching approach — the video-and-practical unit: Lesson 4: Alcohols — Classification, Oxidation, Substitution and Dehydration →

Lesson 7: Alcohols: Oxidation, Substitution & Dehydration