We have been working toward incorporating Raman spectroscopy into the organic chemistry curriculum. A natural entry point for the consideration of Raman spectra is during the study of functional groups and molecular structure using infrared (IR) spectroscopy. Universally studied in organic chemistry curricula, IR spectra contain information about the presence or absence of functional groups. When considering functional groups it is convenient to focus on bond vibrations. Functional group vibrations such as hydroxyl, nitrile, and carbonyl stretches are particularly useful because they are found in many compounds studied in organic chemistry lecture and laboratory. In addition, their permanent dipoles render them IR-active in most structural contexts. However, other relevant functional groups are only observed by IR spectroscopy when the structural context does not result in dipole cancellation. These groups – for example, internal or symmetric alkene and alkynes – are typically Raman-active even when they do not have pronounced IR signals. Introducing examples of symmetric and asymmetric bond stretches allows reinforcement of foundational concepts such as (a) IR signals require a change in dipole upon bond vibration; (b) bonds are vibrating even if they are IR-silent due to cancellation of dipoles; (c) multiple detection methods are required to fully characterize a molecular system. In this presentation, the effectiveness of actual classroom examples used to introduce Raman spectroscopy while reinforcing IR spectroscopy and its application to the analysis of molecular structure will be discussed. These examples include a reaction product that students prepared in laboratory. In addition, comparative IR and Raman spectra for a curated collection of molecules being considered for future incorporation into the organic chemistry curriculum will be presented.

Introducing organic chemistry students to Raman spectroscopy using functional group and structural analysis

2019 Spring National Meeting

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