Free Radical Substitution in Alkanes Explained

The video explains free radical substitution of alkanes, highlighting their unreactive nature due to non-polarity and strong bonds. It introduces free radicals as reactive species and details the substitution reaction with halogens, focusing on initiation, propagation, and termination stages. The video also addresses the problem of side products and concludes with teaching notes on notation.

Why are alkanes considered unreactive molecules?

• They are polar molecules.

• They are highly electronegative.

• They have weak bonds.

• They are non-polar and have strong bonds.

What is a free radical?

• A molecule with paired electrons.

• A species with an unpaired electron.

• A non-reactive species.

• A stable molecule.

What happens during the initiation stage of free radical substitution?

• Bonds are strengthened.

• Electrons are paired.

• Molecules are stabilized.

• Free radicals are formed by homolytic fission.

In the propagation stage, what does a bromine-free radical do?

• It forms a stable molecule.

• It reacts with a methane molecule.

• It reacts with another bromine-free radical.

• It becomes unreactive.

What is the result of the termination stage in free radical substitution?

• Formation of stable molecules.

• Continuation of the chain reaction.

• Formation of more free radicals.

• No change in the reaction.

What is a major problem with free radical substitution of alkanes?

• It results in a range of side products.

• It requires high temperatures.

• It is a very slow reaction.

• It produces only one product.

What can happen if a bromine-free radical reacts with bromomethane?

• Formation of dibromomethane.

• Formation of water.

• Formation of methane.

• Formation of ethane.

Why might longer-chain alkanes produce a wide range of products?

• They are more reactive.

• They have more hydrogen atoms.

• They can form different isomers.

• They are less stable.

What is the significance of curly half-arrows in free radical substitution?

• They show the formation of free radicals.

• They are not required by AQA, Edexcel, and OCR.

• They indicate the movement of electron pairs.

• They are required by all exam boards.

Which exam boards do not require the use of curly half-arrows?

• All exam boards require them

• OCR only

• AQA and Edexcel only

• AQA, Edexcel, and OCR