Photodissociation of Chlorine Gas

Cl2 → 2Cl·

Overview

UV or visible light (< 500 nm) cleaves the Cl–Cl bond homolytically to produce two chlorine free radicals. This is the initiation step in many radical chain reactions, including the chlorination of hydrocarbons. Each chlorine radical can propagate thousands of reaction cycles before termination.

Everyday Example

The chlorination of methane to produce chloromethane begins with this UV-initiated splitting of chlorine gas.

Industrial Importance

Free radical chlorination is used to manufacture chlorinated solvents, PVC (polyvinyl chloride), and various chlorinated organic compounds.

Properties

Type
Photochemical
Reversible
No
Energy
Endothermic
ΔH
242.6 kJ/mol

Related Reactions

Chlorophyll Fluorescence Cis-Trans Isomerization of Retinal Dye-Sensitized Solar Cell (Grätzel Cell) Firefly Bioluminescence (Luciferin Oxidation) Luminol Chemiluminescence Ozone Decomposition by UV Ozone Formation by UV Light Photocatalytic NOx Removal Photocatalytic Water Splitting (TiO₂) Photochemical Cycloaddition ([2+2])

Frequently Asked Questions

What is the equation for Photodissociation of Chlorine Gas?
The balanced equation is: Cl₂ → 2Cl·.
What type of reaction is Photodissociation of Chlorine Gas?
Photodissociation of Chlorine Gas is a photochemical reaction.
Is Photodissociation of Chlorine Gas exothermic or endothermic?
Photodissociation of Chlorine Gas is endothermic (absorbs energy). The enthalpy change (ΔH) is 242.6 kJ/mol.