Eduqas A-Level Chemistry: C3 (Chemistry of Carbon Compounds) overview

What this topic demands

Topic C3 of Eduqas A-Level Chemistry is the AS organic block, building from the language of carbon compounds to the reactions and mechanisms of the main functional groups and finishing with the analytical techniques used to identify them. The examiners reward accurate mechanisms, precise reagents and conditions, and confident structure deduction from spectra.

This guide walks through C3 in specification order and sets out the exam patterns Eduqas repeats. Each topic has a matching dot-point page with practice questions; this overview ties them together.

The language of organic chemistry

Organic compounds (C3.1) covers functional groups and homologous series, IUPAC nomenclature, the five ways of writing formulae (empirical, molecular, structural, displayed and skeletal), general formulae, and the categories of isomerism (structural and stereo). This is the grammar that the rest of the block uses.

Hydrocarbons and their mechanisms

Hydrocarbons (C3.2) covers alkanes (their source in crude oil, combustion and free-radical substitution under UV) and alkenes (electrophilic addition with the major product set by carbocation stability and Markownikoff's rule, plus addition polymerisation). The mechanisms, with correct curly arrows and radical notation, are central.

The functional-group reactions

Halogenoalkanes (C3.3) covers nucleophilic substitution (giving alcohols, nitriles and amines), elimination to alkenes, the bond-enthalpy explanation of hydrolysis rate, and the ozone-depleting impact of CFCs.

Alcohols and carboxylic acids (C3.4) covers classifying alcohols, oxidising primary alcohols to aldehydes then acids and secondary alcohols to ketones (orange to green dichromate), dehydration to alkenes, and the acidity of carboxylic acids and their esterification.

Identifying molecules

Instrumental analysis (C3.5) introduces mass spectrometry of organic molecules (the molecular ion gives the relative molecular mass; fragmentation reveals the groups lost) and infrared spectroscopy (O-H, C=O and C-H absorptions), and the synoptic skill of combining the two to deduce a structure.

How this topic is examined

A typical Eduqas profile for C3:

• Mechanisms. Free-radical substitution (initiation, propagation, termination), electrophilic addition (with curly arrows and the carbocation), and nucleophilic substitution and elimination.
• Reactions and naming. Predicting products, recalling reagents and conditions, and naming compounds by IUPAC rules.
• Functional-group identification. Oxidation colour changes, the carbonate test for acids and the bromine-water test for alkenes.
• Spectra. Reading molecular ions and fragments, identifying bonds from infrared absorptions, and deducing structures.

Check your knowledge

A mix of recall, mechanism and structure questions across C3. Attempt them under timed conditions, then check against the solutions.

1. Name the mechanism by which methane reacts with chlorine in UV light. (1 mark)
2. State the reagent and conditions for converting ethene into ethanol, and name the reaction type. (2 marks)
3. State what is observed and the organic product when 1-bromobutane reacts with warm aqueous sodium hydroxide. (2 marks)
4. Name the organic product of fully oxidising propan-1-ol with acidified potassium dichromate(VI). (1 mark)
5. State the bonds responsible for infrared absorptions at about $3300\ \text{cm}^{-1}$ (broad) and $1700\ \text{cm}^{-1}$. (2 marks)
6. Explain why tertiary alcohols are not oxidised by acidified dichromate. (2 marks)