Introducing Students to a Synthetic and Spectroscopic Study of the Free Radical Chlorine Dioxide

Abstract

This advanced undergraduate chemistry laboratory exercise takes advantage of the unique spectroscopic properties of the free radical chlorine dioxide to allow for a direct comparison of its symmetric stretch in both the ground and excited states. It incorporates several subject areas covered in an undergraduate chemistry degree (synthesis, spectroscopy, and computational chemistry) and is suitable for an advanced level inorganic, physical, or integrated chemistry laboratory course. Students synthesize aqueous chlorine dioxide, analyze a vibronic progression of the symmetric stretch in the excited state using UV−vis spectroscopy, and also record the energy of the symmetric stretch in the ground state using Raman spectroscopy. In addition to offering advanced undergraduate students the opportunity to study the chemistry of a radical first-hand, this exercise also reinforces the use of synthetic techniques for the purpose of studying how a molecule's physical properties vary with the electronic state. An optional computational chemistry component includes optimizing the geometries of the ground and excited states of the radical, calculating the charge, and comparing computed harmonic vibrational frequencies to the experimental data.

Viking Spectrophotometer: A Home-Built, Simple, and Cost-Efficient Absorption and Fluorescence Spectrophotometer for Education in Chemistry

“…In the fields of chemistry and biochemistry, several applications of PBL methodology in education have been reported using commercial UV–vis and fluorescence spectrophotometers, e.g., to analyze different substances: beer, drugs, honey, lipids, nucleic acids, and proteins . A large number of other spectroscopy experiments focused on studying processes using a commercial spectrophotometer to obtain data. , …”

“…17 A large number of other spectroscopy experiments focused on studying processes using a commercial spectrophotometer to obtain data. 18,19 UV−vis spectrophotometers are arguably one of the most popular spectroscopy tools used in chemistry laboratories, allowing the illustration of important concepts like concentration-and path length-dependent absorption, 20 reaction dynamics, 21 or the dependence of the HOMO−LUMO gap on the conjugation length. 22 For many years, these and similar experiments were employed at Lund University during Bachelor-level undergraduate education (second-and third-year university-level education) and a Master-level course (fourth-year university-level education).…”

A Mechanistic Investigation of the N-Hydroxyphthalimide Catalyzed Benzylic Oxidation Mediated by Sodium Chlorite

“…The UV spectrum of a 4.37 × 10 –4 M aqueous solution of chlorine dioxide is overlaid on each spectrum in Figure 3 (yellow trace), which displays a characteristic peak at λ max 360 nm with vibronic coupling evident in the spectrum. 59 Conducting a reaction at 4.80 × 10 –3 M concentration of 10 confirmed the formation of chlorine dioxide ( Figure 3 a), which had been initially proposed because of the intense yellow coloration of the reaction mixture. When the NHPI catalyst was omitted from the reaction mixture, the formation of chlorine dioxide was detected by UV/vis spectroscopy, indicating that this substance was also present in any uncatalyzed reaction pathway albeit at significantly lower concentrations ( Figure 3 b).…”

“…The oxidation of fluorene 10 was monitored by UV spectroscopy (Figure ). The UV spectrum of a 4.37 × 10 –4 M aqueous solution of chlorine dioxide is overlaid on each spectrum in Figure (yellow trace), which displays a characteristic peak at λ max 360 nm with vibronic coupling evident in the spectrum . Conducting a reaction at 4.80 × 10 –3 M concentration of 10 confirmed the formation of chlorine dioxide (Figure a), which had been initially proposed because of the intense yellow coloration of the reaction mixture.…”