Write the initiation step for the chlorination of methane and state what happens in it.

The initiation step is Cl₂ → 2Cl• in ultraviolet light, in which the chlorine–chlorine bond undergoes homolytic fission to produce two chlorine radicals.

Write the two propagation steps for the chlorination of methane.

The propagation steps are Cl• + CH₄ → •CH₃ + HCl and then •CH₃ + Cl₂ → CH₃Cl + Cl•.

CCEA A-Level Chemistry 1110

Formulae, Equations and Amounts of Substance

Topic overview Ionic charges and the formulae of compound ions Writing and balancing full and ionic equations The mole, molar mass and Avogadro's constant Reacting masses and reactants in excess Hydrated salts and water of crystallisation

Atomic Structure

Topic overview Protons, neutrons and electrons Atomic number, mass number and the composition of ions Isotopes and relative isotopic mass Relative atomic, molecular and formula mass Mass spectra and relative atomic mass calculations Mass spectra of diatomic elements Electronic configuration and the building up principle Orbitals, electron spin and orbital shapes The s-, p-, d- and f-blocks of the Periodic Table Ionisation energies and their equations Trends in ionisation energy as evidence for shells and subshells

Bonding

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Intermolecular Forces and Structure

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Shapes of Molecules and Ions

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Redox

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The Halogens

Topic overview Colours, physical states and solubility of the halogens Chlorine with water and the treatment of drinking water Disproportionation of the halogens with sodium hydroxide Oxidising ability and displacement reactions Solid halides with concentrated sulfuric and phosphoric acid

Acid-Base Titrations

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Qualitative Tests

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Formulae and Amounts of a Substance

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Nomenclature and Isomerism in Organic Chemistry

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Alkanes

Topic overview Alkanes as saturated hydrocarbons Boiling points of alkanes and van der Waals' forces Boiling points of branched isomers Complete and incomplete combustion of alkanes Pollutants from alkane fuels and the atmosphere Catalytic converters Radicals, homolytic fission and heterolytic fission Free radical substitution of alkanes

Alkenes

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Halogenoalkanes

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Alcohols

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Aldehydes and Ketones

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Carboxylic Acids

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Derivatives of Carboxylic Acids

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Aromatic Chemistry

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Spectroscopy and Chromatography

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Volumetric Analysis

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Transition Metals

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Electrode Potentials

Topic overview Standard electrode potential Types of half-cell Cell representation and calculating emf Non-rechargeable, rechargeable and fuel cells The hydrogen–oxygen fuel cell Electrode potentials and reactivity

Amines

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Amides and Polymers

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Amino Acids and Proteins

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Chemistry in Medicine

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Alkanes

Free radical substitution of alkanes

3 things to know
Unit AS 2

Overview

Mechanism operates when methane reacts with chlorine and three stages of the free radical substitution mechanism.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

What type of mechanism operates when methane reacts with chlorine?

Key term

What conditions are required for the halogenation of an alkane?

Key term

Write the overall equation for the reaction of methane with chlorine to give chloromethane.

Questions from this subtopic

Each one with the model answer underneath.

1
What type of mechanism operates when methane reacts with chlorine?
Model answer
The reaction proceeds by free radical substitution, in which a chlorine radical replaces a hydrogen atom on the alkane.
2
What conditions are required for the halogenation of an alkane?
Model answer
Ultraviolet light, such as sunlight, is required, with the alkane and the halogen mixed in the gas phase.
3
Write the overall equation for the reaction of methane with chlorine to give chloromethane.
Model answer
The equation is CH₄(g) + Cl₂(g) → CH₃Cl(g) + HCl(g).
4
Name the three stages of the free radical substitution mechanism.
Model answer
The three stages are initiation, propagation and termination.
5
Write the initiation step for the chlorination of methane and state what happens in it.
Model answer
The initiation step is Cl₂ → 2Cl• in ultraviolet light, in which the chlorine–chlorine bond undergoes homolytic fission to produce two chlorine radicals.
6
Write the two propagation steps for the chlorination of methane.
Model answer
The propagation steps are Cl• + CH₄ → •CH₃ + HCl and then •CH₃ + Cl₂ → CH₃Cl + Cl•.

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Free radical substitution of alkanes

Overview

What you need to know

What type of mechanism operates when methane reacts with chlorine?

What conditions are required for the halogenation of an alkane?

Write the overall equation for the reaction of methane with chlorine to give chloromethane.

Questions from this subtopic

What type of mechanism operates when methane reacts with chlorine?

What conditions are required for the halogenation of an alkane?

Write the overall equation for the reaction of methane with chlorine to give chloromethane.

Name the three stages of the free radical substitution mechanism.

Write the initiation step for the chlorination of methane and state what happens in it.

Write the two propagation steps for the chlorination of methane.

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Alkanes, on a schedule.