Tuesday, 11:00 am Room 1315 February 27, 2018 Chemistry Building

Professor  Ned  Sibert  

Department  of  Chemistry  University of Wisconsin - Madison

The CH and OH stretch vibrational frequencies are sufficiently distinct from other vibrational frequencies, that their presence in an IR spectrum is a good indicator of the presence these functional groups. In this talk, we extend these ideas. It turns out that both the OH and CH stretches exhibit a surprising sensitivity to molecular structure. If the IR spectra are high enough resolution, then we can take advantage of this sensitivity, and use the spectra to provide information regarding molecular structure and local environment. I will describe the interplay between theoretical and experimental groups that has enabled the development of models with which we are able to determine what the experimental spectra tell us about molecular structure and local environments. To illustrate these ideas, I will show how IR spectra help answer the following three questions. Where does the Na+ ion go when attached to cyclohexane molecule? If we ‘mix’ seven water molecules with a benzene molecule, how do the water molecules arrange themselves in order to minimize the total energy of the system? How long does the tail of an alkylbenzene molecule C6H5-(CH2)n-CH3 have to be, before the chain bends back on itself? Refreshments will be available prior to seminar at 10:45 a.m. in the Shain Atrium

Graduate Students can meet with the speaker in Room 8305F at 1:00 pm

CH and OH Stretch Vibrations as Probes of Local Environment