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Aryl chlorides (ArCl) or aryl fluorides (ArF) were used in polycondensation reactions to form poly(arylene ether sulfone)s (PAES). Interestingly, the kinetics of the ArF reaction fit a third-order rate law, which is attributed to the activation of the carbon–fluorine bond by two potassium cations (at least one bound to phenolate), which form a three-body complex. The ArCl monomer follows a second-order rate law, where a two-body complex forms at the initial state of the aromatic nucleophilic substitution (S N Ar) pathway. These metal cation-activated complexes act as intermediates during the attack by the nucleophile. This finding was reproduced with either the potassium or the sodium counterion (introduced via potassium carbonate or sodium carbonate). Through a combination of experimental analysis of reaction kinetics and computational calculations with density functional theory (DFT) methods, the present work extends the fundamental understanding of polycondensation mechanisms for two aryl halides and highlights the importance of the CX–metal interaction(s) in the S N Ar reaction, which is translational to other ion-activated substitution reactions.
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This content will become publicly available on March 11, 2026
Kinetics Experiment on the Reaction of Coumarin-102 with NaOH Using Smartphone Fluorescence Imaging
This paper reports a laboratory experiment that determines the kinetics of the reaction of coumarin-102, a fluorescent dye, with sodium hydroxide. The reaction is studied by monitoring the loss of coumarin-102 fluorescence during ring-opening saponification by hydroxide using smartphone cameras and near-UV (“blacklight”) illumination. The order of the reaction in coumarin-102 is determined by examining the time course of fluorescence decay over time and fitting the data to integrated rate law models. The order of the reaction in sodium hydroxide is determined by varying the concentration of NaOH and comparing the impact on the rate of the reaction. This represents an easy-to-implement kinetics experiment that uses an engaging phenomenon (fluorescence), a convenient data-acquisition technology (smartphone cameras) and an important image-processing software program (ImageJ). This gives students the ability to work with the determination of the rate law for both coumarin-102 and for sodium hydroxide, using complementary methods. This experiment is both informative and enjoyable for students, enabling them to directly observe kinetics—quite literally with open eyes—making scientific concepts more tangible and engaging. The experiment has also been adapted in a manner consistent with the principles of evidence-centered design using content of kinetics and the scientific practice of mathematical reasoning.
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- Award ID(s):
- 2111446
- PAR ID:
- 10577368
- Editor(s):
- Holme, Thomas A
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Journal of Chemical Education
- Edition / Version:
- 1
- Volume:
- 102
- Issue:
- 3
- ISSN:
- 0021-9584
- Page Range / eLocation ID:
- 1199 to 1207
- Format(s):
- Medium: X Other: *.docx
- Sponsoring Org:
- National Science Foundation
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