Modern high field NMR is a useful tool for “discovering chemical concepts” in the physical chemistry laboratory.  Since these instruments can easily measure the NMR of small molecules in the vapor phase, it is easy to compare the vapor phase NMR to that of the neat liquid or to the pattern calculated using DFT calculations.  Students quickly discover that while the only difference in the proton NMR of benzene liquid and vapor is a solvent shift caused by the paramagnetic oxygen in the vapor NMR, the pattern observed for methanol liquid and vapor are dramatically different.  DFT-B3LYP-GIAO establish that hydrogen bonding in the liquid causes these differences.   The mass susceptibility and magnetic moment of O2 are determined from the solvent shift.  Since the NMR signal, intensity follows Beer’s Law, the enthalpy of vaporization can also be measured using variable temperature NMR.  Results for these exercises will be presented.

Physical chemistry laboratory experiments using vapor phase NMR

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.