Developing a Safe and Versatile Chemiluminescence Demonstration for Studying Reaction Kinetics Abbas Eghlimi,* Hasan Jubaer, Adam Surmiak, and Udo Bach Department of Chemical Engineering, Monash University, Clayton 3800, Australia * S Supporting Information ABSTRACT: Although chemiluminescent reactions are generally used in demonstrations to pique students’ interest in chemistry, they may serve as a great tool for studying reaction kinetics. In this paper, we briefly present an overview of the basics of chemiluminescent kinetics and introduce a safe and robust formulation for making chemiluminescent reactions using citrate- based solvents suitable for chemical studies. The rates of chemiluminescence reactions were quantified using open-source Arduino-development-board projects and ubiquitous photoresistor-based sensors. The simple and versatile formulation as well as the data logging proposed in this work provide instructors with an easy, interesting, and cost-effective tool for teaching reaction kinetics at room temperature. The experiment can be tuned to accommodate for time constraints and various levels of complexity in postprocessing. On the basis of the proposed formulation, a procedure for model demonstration has been described. The proposed methodology was supported by providing an example of data collected and postprocessed by first-year undergraduate students. This work will contribute to improving the pedagogical applications of chemiluminescent reactions. KEYWORDS: First-Year Undergraduate/General, Second-Year Undergraduate, Chemical Engineering, Demonstrations, Organic Chemistry, Public Understanding/Outreach, Esters, Fluorescence Spectroscopy ■ BACKGROUND INFORMATION Chemiluminescent reactions have proved to be intriguing chemical reactions that motivate students to learn numerous chemistry concepts in a variety of settings and demonstra- tions. 1−3 These reactions also are fundamental to a popular commercial product called “glow sticks”. Although several other formulations exist, peroxyoxalate-based glow sticks have dominated the market, because they are the most efficient nonenzymatic chemiluminescent reactions. 4 In these products, hydrogen peroxide (H 2 O 2 ) reacts with a diaryl oxalate diester (e.g., bis(2-carbopentyloxy-3,5,6-trichlorophenyl) oxalate, CPPO) in the presence of a base acting as catalyst and produces oxalyl chloride. The unstable intermediate oxalyl chloride quickly converts into another high-energy intermedi- ate, 1,2-dioxetanedione, which eventually decomposes into carbon dioxide (CO 2 ), releasing energy. This released energy, which would otherwise heat up the mixture, can be absorbed by a fluorescer, generating light via chemiluminescence. The energy is used to excite electrons in the dye and consequently, the dye releases light upon the electrons’ relaxation back to ground state via radiative decay. In other words, the system extracts the energy released by the exothermic reaction to produce light. This is summarized in Scheme 1. ■ KINETICS OF PEROXYOXALATE CHEMILUMINESCENCE Both the wavelength (i.e., color, see Figure 1) and intensity of the light produced by the glow stick depend on the intrinsic properties of the dye (among other things, which will be discussed). However, by selecting any dye suitable for the application and not varying it, chemiluminescent reactions can be utilized to teach the basics of reaction kinetics at different levels. 5−8 Chemiluminescent reactions are generally used as an analytical tool in chromatography 9 and to determine the kinetics of other chemical reactions. 10,11 However, their innate kinetics at room temperature can be utilized to study reaction kinetics in an intriguing manner. In order to discuss the reaction kinetics in detail, the efficiency of a chemiluminescent reaction must be elaborated first. The efficiency of a chemiluminescent reaction, Φ CL , is the number of light quanta emitted per molecule of reactants. 12 In Received: August 20, 2018 Revised: January 17, 2019 Scheme 1. Working Mechanism of the Indirect Chemiluminescence of Peroxyoxalate-Based Glow Sticks with CPPO and H 2 O 2 Reagents Demonstration pubs.acs.org/jchemeduc Cite This: J. Chem. Educ. XXXX, XXX, XXX-XXX © XXXX American Chemical Society and Division of Chemical Education, Inc. A DOI: 10.1021/acs.jchemed.8b00614 J. Chem. Educ. XXXX, XXX, XXX−XXX Downloaded via UNIV OF TEXAS AT DALLAS on February 8, 2019 at 20:29:24 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.