Luminol Chemiluminescence
C8H7N3O2 + H2O2 → 3-aminophthalate + N2 + hν (blue light)
Overview
Luminol reacts with hydrogen peroxide in the presence of a catalyst (typically iron from hemoglobin in blood) to produce 3-aminophthalate in an excited electronic state. As the molecule relaxes, it emits blue light (425 nm). The iron in blood catalyzes this reaction, making it a powerful forensic tool.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Reactant | Hydrogen Peroxide H₂O₂ | 1 | (aq) |
Everyday Example
Crime scene investigators spray luminol solutions in dark rooms to detect invisible bloodstains that glow blue.
Industrial Importance
Luminol is used in forensic science, analytical chemistry, environmental monitoring, and biological research for detecting trace metals and reactive oxygen species.
Properties
- Type
- Photochemical
- Reversible
- No
- Energy
- Exothermic
- ΔH
- -300.0 kJ/mol
- Catalyst
- Fe²⁺ (from hemoglobin)
Related Reactions
Chlorophyll Fluorescence
Cis-Trans Isomerization of Retinal
Dye-Sensitized Solar Cell (Grätzel Cell)
Firefly Bioluminescence (Luciferin Oxidation)
Ozone Decomposition by UV
Ozone Formation by UV Light
Photocatalytic NOx Removal
Photocatalytic Water Splitting (TiO₂)
Photochemical Cycloaddition ([2+2])
Photochemical Smog Formation (NO₂ Photolysis)
Frequently Asked Questions
What is the equation for Luminol Chemiluminescence?
The balanced equation is: C₈H₇N₃O₂ + H₂O₂ → 3-aminophthalate + N₂ + hν (blue light).
What type of reaction is Luminol Chemiluminescence?
Luminol Chemiluminescence is a photochemical reaction.
Is Luminol Chemiluminescence exothermic or endothermic?
Luminol Chemiluminescence is exothermic (releases energy). The enthalpy change (ΔH) is -300.0 kJ/mol.
What conditions are needed for Luminol Chemiluminescence?
This reaction requires a catalyst (Fe²⁺ (from hemoglobin)).