DOI
https://doi.org/10.1021/acs.jchemed.9b00405

Summary
This article describes an adaption of the rovibrational spectroscopy of carbon dioxide experiment that can be used as a stand-alone experiment or in conjunction with a traditional hydrogen chloride experiment. The experimental methodology described here utilizes a “compare and contrast” approach between HCl and CO2 experiments to reinforce the systems thinking and green chemistry aspects, in addition to creating scaffolded learning of rovibrational spectroscopy concepts.
The study of rovibrational spectra is an important component of any undergraduate physical chemistry curriculum, both in the laboratory through various experiments and through theoretical treatment in lecture-based instruction.
First, the authors provide information for rovibrational spectroscopy theory. In order to perform the experiment to fully meet the green chemistry goals, a student simply has to acquire an IR absorption spectrum of air. Information regarded this approach is also provided.
Then, the educational advantages of carbon dioxide instead of the traditional used hydrogen chloride are discussed. A number of properties of CO2 that facilitate the deeper understanding of rovibrational spectroscopy beyond the basics covered during the analysis of HCl, are presented.
Moreover, by applying a systems thinking approach to the green chemistry principle of reducing or eliminating toxic reagents, the proposed experiments use only ambient atmospheric carbon dioxide to completely eliminate any purchased reagent. Additionally, without the need for vacuum lines, pumps, traps, and IR gas cells to prepare a sample, instructors can discuss with students the concept of the total chemical footprint of an experiment in relation to not only the reagents but the equipment used to perform the experiment. Therefore, by having students perform both traditional HCl and green CO2 experiments, the reduction of the total chemical footprint of the CO2 experiment relative to the HCl experiment becomes quite apparent and should be readily recognizable by students. Finally the use of carbon dioxide also facilitates a discussion of issues related to climate change that reinforces the systems thinking methodology to green chemistry.

Relevance for Complex Systems Knowledge
This paper deals with system thinking and green chemistry and proposes an approach to reimagine higher education as it describes an alternative experiment for the study of rovibrational spectra, which is a fundamental component of most physical chemistry curricula.
The experimental methodology described here utilizes a “compare and contrast” approach between HCl and CO2 experiments to reinforce the systems thinking and green chemistry aspects, in addition to creating scaffolded learning of rovibrational spectroscopy concepts. Although the CO2 experiment could also be adopted as a stand-alone experiment, the full systems thinking approach is realized when both the HCl and CO2 experiments are performed.

Point of Strength
The point of strength of this paper is that it presents an experiment through which students can be introduced to the concept of the total chemical footprint, which is a product of a systems thinking approach to green chemistry.