|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!
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