Eduqas A Level Chemistry Component 2: Organic Chemistry and Analysis Exam Questions

About Eduqas A Level Chemistry Component 2: Organic Chemistry and Analysis

Component 2 of the Eduqas A Level Chemistry course focuses on organic chemistry and the techniques used to identify organic compounds. It covers optical and E/Z stereoisomerism, the structure and reactions of benzene, alcohols and phenols, aldehydes and ketones, carboxylic acids and their derivatives, amines including diazonium chemistry, amino acids and proteins, and organic synthesis and analysis. It builds on the first year organic topics of hydrocarbons, halogenoalkanes and alcohols. Examiners regularly ask for mechanisms (electrophilic substitution and nucleophilic addition), multi-step synthesis routes with conditions, chemical tests with observations, and structure deduction from combined NMR, IR and mass spectra.

What you need to know

• OA1 Stereoisomerism and aromaticity Optical isomers have a chiral centre and rotate plane-polarised light in opposite directions. Benzene has a delocalised pi system that makes it more stable than a Kekule structure; it undergoes electrophilic substitution such as nitration and halogenation, and Friedel-Crafts reactions.
• OA2.1 Alcohols and phenols Phenol is weakly acidic, reacts with NaOH but not with carbonates, and reacts readily with bromine water to give a white precipitate of 2,4,6-tribromophenol. Iron(III) chloride gives a purple colour with phenols.
• OA2.2 Aldehydes and ketones Both give an orange precipitate with 2,4-DNPH. Aldehydes are oxidised by Tollens' reagent (silver mirror) and Fehling's solution (red precipitate). Nucleophilic addition of HCN gives hydroxynitriles; NaBH4 reduces carbonyls to alcohols. The iodoform test identifies CH3CO groups.
• OA2.3 Carboxylic acids and derivatives Acids form esters and react with carbonates. Acyl chlorides react readily with water, alcohols and amines. Esters are hydrolysed by acid or alkali, and nitriles can be hydrolysed to acids.
• OA3 Amines, amino acids and proteins Amines are bases due to the nitrogen lone pair. Phenylamine reacts with nitrous acid below 10 C to form a diazonium salt, which couples with phenols to form azo dyes. Amino acids form zwitterions and join by peptide links.
• OA4 Synthesis and analysis Plan routes that change functional groups and chain length (for example via nitriles). Use 13C and 1H NMR (chemical shift, integration, n+1 splitting), IR, mass spectra and chromatography to identify products and check purity.

Common mistakes in Component 2: Organic Chemistry and Analysis

• Forgetting the temperature for diazotisation. It must be kept below about 10 C because diazonium salts decompose at higher temperatures.
• Saying phenol reacts with sodium carbonate. Phenol is too weak an acid to release CO2 from carbonates, which is a useful test to separate it from carboxylic acids.
• Drawing the nucleophilic addition mechanism without the lone pair on CN- or without the protonation step.
• Applying the n+1 rule using hydrogens on the same carbon. Count hydrogens on adjacent carbons only.
• Missing conditions in synthesis routes. Each step needs reagents and conditions, such as reflux or temperature.

Try three Component 2: Organic Chemistry and Analysis exam-style questions