Cambridge O Level Chemistry · Syllabus 5070 · Organic Chemistry
Substitution Reaction
What is Substitution Reaction?
A reaction in which one atom, or group of atoms, in a molecule is replaced by a different atom or group of atoms; the displaced atom leaves as part of a second product.
This definition is part of the Organic Chemistry chapter in Cambridge O Level Chemistry.
Questions students ask about Substitution Reaction
What is the difference between an addition reaction and a substitution reaction?
An addition reaction opens a carbon-carbon double bond so that atoms from another molecule join the two carbons, forming exactly one product with nothing displaced — as when ethene reacts with bromine. A substitution reaction replaces one atom or group in a molecule with a different one, and the displaced atom leaves as part of a second product — as when methane reacts with chlorine in ultraviolet light to give chloromethane and hydrogen chloride.