The structure and vibrational modes of propargylene (HCCCH)
The vibrational modes of propargylene were modeled at multiple levels of theory using the CFOUR quantum chemistry package. Then a potential energy plot was produced for two of the unsymmetric modes at both the UHF/CCSD, which allows the α electron orbitals and the β electron orbitals to be different, and ROHF/CCSD, which requires them to be the same except for any electrons which do not form a pair, levels of theory. The theoretical structure and vibrational modes were used to compare the more accurate representation of propargylene to the classic lewis structure version of the molecule and to discuss how resonance is used to show molecules that can not be accurately depicted using a single lewis structure. These calculations were also used to gain insight into the nature of the different energy levels of propargylene and as a starting point for more refined quantum mechanical calculations, which have not yet been carried out.