b S Supporting Information C hemiluminescence is light emission from a chemical reaction. Peroxyoxalate chemiluminescence involves the reaction of oxalate diesters with hydrogen peroxide to generate unstable 1,2-dioxetanedione, which decomposes into electronically excited carbon dioxide (Scheme 1). The excited CO 2 transfers energy to a fluorescer or fluorophore, which releases light upon decay to the ground state. 1,2 Cyalume "light sticks" utilize this same chemistry for emergency lighting, fishing lures, and entertainment. The commercially available oxalate diesters, bis(2,4,6-trichlorophenyl)oxalate (TCPO) and bis(2,4-nitrophenyl)oxalate (DNPO), are typically used in both lecture demonstrations and laboratory experiments in chemiluminescence. 3À6 However, the serious environmental toxicities of the products 2,4,6-trichlorophenol 7 and 2,4-dinitrophenol, 8 as well as exposure to potentially hazardous organic solvent vapors in an open air setting, have encouraged us to redesign this demonstration along greener lines. In our demonstration, hazardous solvents such as dichloromethane are replaced with triacetin, a low volatility, nontoxic, and biodegradable compound, 9 and the oxalate diester is divanillyl oxalate 1, 10 which is readily prepared in one step from the artificial flavoring agent vanillin 2 (Scheme 2). In addition to CO 2 , the product of our chemiluminescent reaction is terrestrially nontoxic vanillin 2. 11 ' AUTHOR INFORMATION