Alkanes and Free Radical Substitution
Alkanes are saturated hydrocarbons that react mainly by free radical substitution under light or heat.
What is Alkanes and Free Radical Substitution?
Alkanes are saturated hydrocarbons that react mainly by free radical substitution under light or heat.
Key formula / rule: Halogenation follows a chain mechanism with three stages.
Key points
- Derive the mechanism of free radical halogenation of an alkane.
- Apply selectivity rules to predict the major halogenation product.
Common exam trap
Proposing an ionic mechanism for alkane halogenation.
Definitions
- Term
Alkanes and Free Radical Substitution
- Meaning
Alkanes are saturated hydrocarbons that react mainly by free radical substitution under light or heat.
- Term
Alkanes and Free Radical Substitution — explanation
- Meaning
Because C-C and C-H σ bonds are strong and non-polar, alkanes are unreactive to ionic reagents. Halogenation proceeds through initiation, propagation and termination steps.
Learning objectives
Derive the mechanism of free radical halogenation of an alkane.
Apply selectivity rules to predict the major halogenation product.
Formulae
- Key point
Halogenation follows a chain mechanism with three stages.
- Key point
Selectivity follows the order tertiary above secondary above primary hydrogen.
- Key point
Alkanes undergo complete combustion to carbon dioxide and water.
Prerequisites
CHE-U4-GO-T1-S2-C2
Common mistakes
Proposing an ionic mechanism for alkane halogenation.
Predicting a single product where a mixture is expected.
Keywords
Alkanes
Free
Radical
Substitution
Practice preview
Which of the following statements correctly describes alkanes?…
easy
What is the hybridization state of carbon atoms in alkanes?…
easy
Under conditions of UV light or high temperature, alkanes primarily undergo which type of reaction?…
easy