Substitution Reactions (Leaving Cert Chemistry): Flashcards

One atom/group replaced by another atom/group in a molecule

Substitution reactions

Atom/group with an unpaired electron

Dot (•) next to chemical symbol

UV light or heat

Bond breaks, each atom gets one electron from the bond

Initiation, Propagation (×2), Termination

$\text{Cl}_2 \rightarrow 2\text{Cl}^\bullet$

$\text{Cl}^\bullet + \text{CH}_4 \rightarrow \text{HCl} + \text{CH}_3^\bullet$

$\text{CH}_3^\bullet + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{Cl}^\bullet$

Free radicals combine to form stable molecules

Ethane ($\text{C}_2\text{H}_6$) from methyl radicals combining

Increase rate by providing more free radicals

$\text{CH}_4 + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{HCl}$

$\text{C}_6\text{H}_{12} + \text{Br}_2 \rightarrow \text{C}_6\text{H}_{11}\text{Br} + \text{HBr}$