| MadSci Network: Chemistry |
Start with a labile (good leaving groups) oxylate bis-ester. React with
alkaline hydrogen peroxide. Peroxide mono-anion attacks the first ester
group to give the ester (unaffected one side) peracid (the other) by
nucleophilic displacement (amplified by the Alpha Effect).
The peracid ionizes and intramolecularly attacks, displacing the other
leaving group and closing to a four-membered ring - two carbons, two
oxygens, both carbons being carbonyls - a diketodioxetane.
The diketodioxetane undergoes spontaneous ring cleavage to give two
molecules of carbon dioxide, one electronically excited. Said excitation
energy can be efficiently transferred to almost any fluorescent species, as
below.
Tetrakis(dimethylamino)ethylene spontaneously reacts with oxygen in the air
to give 2+2 cycloaddition to 3,3,4,4-tetrakis(dimethylamino)dioxetane.
That in turn spontaneously cleaves as above into two molecules of
tetramethylurea, one electronically excited. It gives a (faint) green glow
all by itself.
Aldrichimica Acta 16(3) 59 (1983) Cyalume
A Multicolored Luminescence Demonstration, J. Chem. Ed. 69(10)
827 (1992) (luminol; which is also enhanced by addition of a
little 4,4'-dihydroxybiphenyl).
The H2O2 oxidation of lucigenin (bis-N-methylacridinium nitrate
Aldrich B4,920-3) is modified to provide a slow color change
across the visible spectrum.
Cyalume lightsticks contain dilute hydrogen peroxide (0.5%) in
dioctylphthalate in a thin glass ampoule, and a DOP solution of
oxalate ester and fluorochrome 9,10-bis(phenylethynyl)anthracene.
9,10-bis(phenylethynyl)anthracene (BPEA) (green) [10075-85-1] Fluka 15146
9,10-diphenylanthracene (DPA) (blue) [1499-10-1] Fluka 42785
5,6,11,12-tetraphenylnaphthacene (rubrene) (orange) [517-51-1] Fluka 84027
bis(2-carbopentyloxy-3,5,6-trichlorophenyl)oxalate (CPPO)
[75203-51-9] Aldrich 39,325-8
bis(2-ethylhexyl)phthalate (DOP) (solvent) [117-81-7] Fluka 80032
sodium salicylate (catalyst) [54-21-7] Fluka 71945
35% hydrogen peroxide [7722-84-1] Fluka 95299
Saturate solvent with dye and CPPO. Sonicate to help solvation.
Start with about 50 mg dye (BPEA, DPA or rubrene) in 10 g solvent
with 50 mg CPPO and 5 mg sodium salicylate. CPPO is limiting
reagent. Put a ml in a small vial and add equal volume of
hydrogen peroxide. Mix vigorously. There will be two phases.
Avoid skin contact! Don't cap tightly!
Cyalume sticks use 1-chloro(BPEA) (30 min high intensity yellow-
green) and the 2-chloro isomer (12 hour green). The yellow fluor
is 1,8-dichloro(BPEA). The red fluor is 2,4-di-t-butylphenyl
substituted 1,4,5,8 tetracarboxynapthalene diamide - very deep
red in organic solvents - mixed with dpa gives "white" light
stick, or "hot pink" depending on concentrations. Almost any
fluorescent dye will give light in the oxlate system - rhodamine
640 gives a good red, and BABN the most intense green fluor (not
as stable as BPEA).
1- and 2-chloro(DPA)s are more efficient than DPA and slightly
Stokes-shifted toward the blue-green. Dihydro(DPA) is shifted
towards the purple in emission - quite pretty.
--
Uncle Al Schwartz
http://uncleal.within.net/
http://www.mazepath.com/uncleal/
http://www.ultra.net.au/~wisby/uncleal/
http://www.guyy.demon.co.uk/uncleal/uncleal.htm
(Toxic URLs! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Try the links in the MadSci Library for more information on Chemistry.