Vibrational Spectroscopy of Hexynes: A Combined Experimental and Computational Laboratory Experiment

Recent advances in spectroscopy and computational chemistry facilitate the introduction of current spectroscopic and computational methods at the undergraduate level. Students obtain and analyze experimental and calculated vibrational spectra (infrared and Raman) of a set of alkyne molecules to determine the role of symmetry with respect to gross selection rules. The alkyne functional group should be well-known from organic chemistry with well-resolved vibrational resonances at frequencies familiar to students. Students are able to apply concepts of symmetry, polarizability, and molecular dipoles to the analysis of experimental and computational data. A laboratory activity combining experimental infrared (IR) and Raman spectra, computational DFT methods, and analysis provides students with the ability to analyze how molecular structure and symmetry influence vibrational spectra.