# Hydrocarbons

> CIE A-Level Chemistry · 9701
> Source: https://www.owlsprep.com/study/cie-9701-u13-overview/
> Weight: n/a

This unit introduces hydrocarbons, the simplest organic compounds made only of carbon and hydrogen. We explore saturated (alkanes) and unsaturated (alkenes) hydrocarbons, building the core organic chemistry foundation for all later units.

**Prerequisites:** [Introduction to organic chemistry: nomenclature and bonding](https://www.owlsprep.com/study/cie-9701-u11-introduction-to-organic-chemistry/)

## Learning objectives

- Classify, name and draw structures of alkanes and alkenes
- Relate bonding and structure of hydrocarbons to their physical and chemical properties
- Predict products of common reactions of alkanes and alkenes
- Explain the industrial importance of hydrocarbons
- Recognise core reaction types that apply to all organic chemistry

## Unit at a Glance

Hydrocarbons are the backbone of all organic molecules, from fossil fuels and plastics to biological compounds. This unit progresses from saturated alkanes (only single C-C bonds) to unsaturated alkenes (containing at least one C=C double bond), directly linking their bonding differences to differences in reactivity.

We build from basic structure and nomenclature to key reaction pathways and industrial applications. These fundamentals will be referenced constantly as you move to more complex organic compounds in subsequent units.

This unit covers the following core sub-topics:
- [Alkanes](https://www.owlsprep.com/study/cie-9701-u13-alkanes/) — Covers structure, nomenclature, physical properties, reactions and industrial uses of saturated alkanes.
- [Alkenes](https://www.owlsprep.com/study/cie-9701-u13-alkenes/) — Explores C=C double bond bonding, nomenclature, electrophilic addition reactions, polymerisation and stereoisomerism.

## Common pitfalls

- **Wrong:** Assuming alkanes are completely unreactive
  - Why it fails: Students often confuse low reactivity with polar reagents for no reactivity at all
  - Correct: Remember alkanes readily undergo combustion and radical substitution reactions under the right conditions
- **Wrong:** Numbering alkene chains without prioritising the double bond position
  - Why it fails: Students often count the longest carbon chain but number from the wrong end, giving the double bond a higher locant than needed
  - Correct: Always number the parent chain to give the C=C double bond the lowest possible position number

## Cheatsheet

| Concept | Key Detail |
| --- | --- |
| General formula (acyclic alkanes) | $C_nH_{2n+2}$ |
| General formula (acyclic alkenes) | $C_nH_{2n}$ |
| Typical reaction type (alkanes) | Radical substitution |
| Typical reaction type (alkenes) | Electrophilic addition |
| π bond strength vs σ bond strength | π bonds are weaker than σ bonds, making C=C more reactive |

## What's next

Begin this unit with the first sub-topic, Alkanes, to learn about the structure, properties and reactions of saturated hydrocarbons. After you complete both sub-topics in this unit, you will progress to the next unit covering halogen derivatives of hydrocarbons, which builds directly on the hydrocarbon reactivity fundamentals you will learn here.

- [Alkanes](https://www.owlsprep.com/study/cie-9701-u13-alkanes/)
- [Halogenoalkanes (Next Unit First Sub-Topic)](https://www.owlsprep.com/study/cie-9701-u14-halogenoalkanes/)
- [Alkenes](https://www.owlsprep.com/study/cie-9701-u13-alkenes/)

---

From [OwlsPrep](https://www.owlsprep.com) — free study guides for A-Level, IB, AP and IGCSE, written against the official syllabus. Canonical page: https://www.owlsprep.com/study/cie-9701-u13-overview/