Why Alkanes Are Saturated and Relatively Unreactive
Part of Alkanes — GCSE Chemistry
This how it works covers Why Alkanes Are Saturated and Relatively Unreactive within Alkanes for GCSE Chemistry. Topic 38: Alkanes It is section 5 of 12 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
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Section 5 of 12
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⚙️ Why Alkanes Are Saturated and Relatively Unreactive
The term "saturated" has a precise chemical meaning: every carbon atom forms the maximum possible number of bonds with hydrogen atoms. Because all C-C bonds are single bonds, there is no double bond available to participate in addition reactions.
Why single bonds make alkanes less reactive:
- Single C-C bonds are strong and difficult to break without a catalyst or high energy
- There is no double bond to "open up" and accept additional atoms (compare to alkenes)
- As a result, alkanes only undergo combustion with oxygen (burning) and substitution reactions with halogens (in UV light)
- Alkenes are far more reactive because the C=C double bond can break open and allow addition reactions to occur
Why boiling point increases with chain length:
Longer chains have more electrons and therefore stronger London dispersion forces (a type of intermolecular force) between molecules. More energy is needed to overcome these forces, giving longer alkanes higher boiling points. Methane is a gas at room temperature; waxes (C20+) are solid.