Bis[2,4,5-trichloro-6-(pentyloxycarbonyl)phenyl]oxalate (also known as bis(2,4,5-trichloro-6-carbopentoxyphenyl) oxalate or CPPO) is an organic compound with the formula . A white solid, it is classified as a diester of oxalic acid. It is an active ingredient for the chemiluminescence in glowsticks.[1] It can be synthesized by reacting 2-carbopentoxy-3,5,6-trichlorophenol with oxalyl chloride.
When mixed with hydrogen peroxide in an organic solvent (diethyl phthalate, ethyl acetate, etc...) in the presence of a fluorescent dye CPPO causes the emission of light, following its degradation to 1,2-dioxetanedione (note that many side-groups of the aromatic rings are not shown.):[2]
The reaction rate is pH dependent, and slightly alkaline conditions achieved by adding a weak base, e.g. sodium salicylate, will produce brighter light. Developed by American Cyanamid in the 1960s, the formulation containing CPPO, a fluorescer, and a glass capsule containing hydrogen peroxide and a base catalyst, all in dialkyl phthalate solvents, was marketed as Cyalume.
The following colors can be produced by using different dyes:
| Color | Compound |
|---|---|
| Blue | 9,10-Diphenylanthracene |
| Green | 9,10-Bis(phenylethynyl)anthracene |
| Yellow-green | Tetracene |
| Yellow | 1-Chloro-9,10-bis(phenylethynyl)anthracene |
| Orange | 5,12-Bis(phenylethynyl)naphthacene, Rubrene, Rhodamine 6G |
| Red | 2,4-Di-tert-butylphenyl 1,4,5,8-tetracarboxynaphthalene diamide, Rhodamine 101, Rhodamine B |