Effects of hydrogen bonding on the ring stretching modes of pyridine.
The effects of hydrogen bonding on the ring stretching modes (both ring breathing and triangle) of pyridine are experimentally investigated using noisy light based coherent Raman scattering spectroscopy. Three systems, pyridine/formamide, pyridine/water, and pyridine/acetic acid, provide varying degrees of strength for the diluent-pyridine hydrogen bond complex. Formamide forms a relatively weaker hydrogen bond, while acetic acid essentially fully transfers a proton to pyridine. Both dilution studies and temperature studies are performed on the three systems. Together, these provide a broad context in which a very simple model for the electronic behavior of pyridine is formulated. This model is based on a molecular orbital picture and electrostatic arguments, and it well explains the observed experimental results. Additionally, a new mechanism for the line broadening of the ring breathing mode for the pyridine-water hydrogen bonded complex is proposed.
Berg
Erik R
ER
Department of Chemistry, Concordia College, Moorhead, Minnesota 56562, USA.
Freeman
Sarah A
SA
Green
Daniel D
DD
Ulness
Darin J
DJ
D019342:Acetic Acid / Q000737:chemistry; D005559:Formamides / Q000737:chemistry; D006860:Hydrogen Bonding; D011725:Pyridines / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods; D014867:Water / Q000737:chemistry
D005559:Formamides; D011725:Pyridines; D014867:Water; C031066:formamide; C023666:pyridine; D019342:Acetic Acid