R3.3 Exam Practice
Organic Chemistry
Section B: Data Analysis
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Question 1: Reaction Pathways Deduce
5 marksEthanol can be converted to several organic products.
(a) State the reagent and conditions to oxidise ethanol to ethanal. [2]
(b) State what further oxidation of ethanal produces. [1]
(c) State the reagent and conditions for dehydration of ethanol to ethene. [2]
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(a) Acidified potassium dichromate (K₂Cr₂O₇/H₂SO₄) [1]; distil immediately to prevent further oxidation [1]
(b) Ethanoic acid (CH₃COOH) [1]
(c) Concentrated H₂SO₄ or Al₂O₃ catalyst [1]; heat/reflux at ~170°C [1]
Section C: Structured Questions
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Question 2: Nucleophilic Substitution HL Explain
5 marks(a) Define nucleophile. [1]
(b) Distinguish between SN1 and SN2 mechanisms. [2]
(c) Predict which mechanism a tertiary halogenoalkane would follow. Justify. [2]
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(a) An electron-pair donor / species with a lone pair that attacks an electron-deficient carbon [1]
(b) SN1: two-step, carbocation intermediate, rate depends on [substrate] only [1]; SN2: one-step concerted, rate depends on [substrate][nucleophile] [1]
(c) SN1 [1]; tertiary carbocation is stabilised by three alkyl groups (inductive effect), and steric hindrance prevents SN2 backside attack [1]
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