Chemiluminescence: Synthesis of Cyalume
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Chemiluminescence: Synthesis of Cyalume and Making it Glow
Intro Chemiluminescence is the process whereby light is produced by a chemical reaction. The flashes
of the male firefly in quest of a mate is an example of natural chemiluminescence. In this experiment we
will make Cyalume, the chemical used in “light sticks.” A light stick contains a solution of cyalume
containing a trace catalytic amount of a colorizing agent (catalyst). Inside is a sealed vial of aqueous
hydrogen peroxide. When you bend the light stick, the hydrogen peroxide vial breaks, the hydrogen
peroxide reacts with the cyalume (those are the two stoichiometric reactants), and energy is released. This
energy is absorbed/released by the catalytic colorizing agent, resulting in the bright glow of varying color;
the same stoichiometric reactants can be used, but when different colorizing catalysts are included,
different colors result. Cyalume is an invention of the American Cyanamide Company. In today’s
experiment, we will make some cyalume, then make up two glow solutions: one will use a commercial
colorizer, and the other will use a home-made colorizer that you will synthesize later this semester. (We’ll
use material that students from previous year made.)
Nature of the Energy Release and Glow Formation
The chemistry that forms the color glow in a light stick is shown below. A cyalume is a symmetric
diester, such as 4. It reacts with hydrogen peroxide (red oxygens) by oxygen exchange. Trichlorophenol
(green) is released as each of the two red oxygens of hydrogen peroxide connect to the two blue carbonyl
groups. The 4-memeberd ring “squarate” diester, including the two carbonyls from the original cyalume
and the two oxygens from hydrogen peroxide, is unstable due to ring-strain, and fragments to give two
molecules of carbon dioxide and energy.
The energy released during the fragmentation “excites” a colorizing molecule that must be present.
In other words, an electron in the colorizer gets “excited” from its ground state to an excited state. When
it subsequently relaxes back to the ground state, a photon of energy is released. If the energy gap ∆E
between the excited state and the ground state is in the visible region of the electromagnetic spectrum,
then visible photons of distinctive color are released. This is what causes the bright colors. Since different
colorizers have different ∆E, they release photons of different colors.
