Edexcel A Level Chemistry
Edexcel A Level Chemistry Topic 17: Organic Chemistry II Exam Questions
Free Edexcel A Level Chemistry exam questions for Topic 17: Organic Chemistry II, with a mark scheme for every pack. Covers chirality and optical isomerism, aldehydes and ketones, nucleophilic addition, carbonyl tests, carboxylic acids, esters, acyl chlorides and their reactions.
Topic 17: Organic Chemistry II exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel A Level Chemistry Topic 17: Organic Chemistry II
Topic 17 of Edexcel A Level Chemistry, Organic Chemistry II, extends organic chemistry to optical isomerism and carbonyl-containing compounds. You identify chiral centres, explain how enantiomers rotate plane-polarised light, and link optical activity to mechanisms: SN1 gives a racemic mixture while SN2 gives inversion. Aldehydes and ketones are covered through oxidation and reduction, nucleophilic addition of HCN, and tests with Fehling's or Benedict's solution, Tollens' reagent, 2,4-DNPH and iodine in alkali. The topic then covers carboxylic acids, esters, acyl chlorides and polyesters, including their preparation and reactions. It is assessed in Paper 2. Examiners regularly test the nucleophilic addition mechanism and identification tests.
What you need to know
- Optical isomerism A chiral carbon has four different groups attached. Enantiomers are non-superimposable mirror images that rotate plane-polarised light in opposite directions, and a racemic mixture has no overall effect.
- Optical activity and mechanisms SN2 attacks from the opposite side, inverting the configuration. SN1 and nucleophilic addition to a planar carbonyl allow attack from either side, giving a racemic mixture.
- Aldehydes and ketones Formed by oxidation of primary and secondary alcohols. Reduced by LiAlH4 in dry ether to alcohols. Aldehydes are oxidised further to carboxylic acids.
- Nucleophilic addition HCN in the presence of KCN adds across C=O to give a hydroxynitrile. CN- attacks the delta positive carbon, then the alkoxide intermediate is protonated.
- Carbonyl tests 2,4-DNPH gives an orange precipitate with any carbonyl. Fehling's or Benedict's solution gives a red precipitate and Tollens' reagent a silver mirror with aldehydes only. Iodine in alkali gives yellow CHI3 with CH3CO- groups.
- Carboxylic acids Made by oxidising primary alcohols or aldehydes, or hydrolysing nitriles. They react with LiAlH4 (reduction), bases and carbonates, alcohols (esterification) and PCl5 (acyl chlorides).
- Esters and acyl chlorides Esters are hydrolysed by acid (reversible) or alkali (complete). Acyl chlorides react with water, alcohols, concentrated ammonia and amines, releasing HCl. Polyesters form from diols and dicarboxylic acids.
Common mistakes in Topic 17: Organic Chemistry II
- Drawing two enantiomers that are actually identical when one is rotated.
- Saying a racemic mixture is not chiral; each molecule is chiral but the rotations cancel out.
- Forgetting that NaBH4 or LiAlH4 do not reduce C=C double bonds.
- Saying ketones give a silver mirror with Tollens' reagent.
- Writing the product of alkaline ester hydrolysis as the carboxylic acid rather than its salt.
Try three Topic 17: Organic Chemistry II exam-style questions
1. Explain why the reaction of propanal with HCN and KCN produces a product that does not rotate plane-polarised light. (3 marks)
Show the mark scheme answer
The C=O group is planar (trigonal planar); CN- attacks equally from either side; equal amounts of both enantiomers form, a racemic mixture, so rotations cancel.
2. Describe a test to distinguish propanal from propanone, giving results. (3 marks)
Show the mark scheme answer
Warm with Fehling's solution (or Tollens' reagent); propanal gives a red precipitate (silver mirror); propanone shows no change (stays blue or colourless).
3. Write an equation for the reaction of ethanoyl chloride with ethanol and name the organic product. (2 marks)
Show the mark scheme answer
CH3COCl + C2H5OH → CH3COOC2H5 + HCl; ethyl ethanoate.
Topic 17: Organic Chemistry II FAQs
What does Edexcel A Level Chemistry Topic 17 Organic Chemistry II cover?
It covers optical isomerism, aldehydes and ketones with their tests and nucleophilic addition, carboxylic acids, esters, acyl chlorides and polyesters.
Which paper is Organic Chemistry II examined in?
Topic 17 is assessed in Paper 2, Advanced Organic and Physical Chemistry, and in Paper 3.
How do I link optical isomerism to mechanisms?
Learn that SN2 inverts the configuration at a chiral carbon, while SN1 and addition to planar C=O give racemic mixtures, and be ready to explain why.
