Seminar by Prof. Edwin L.Sibert III, Department of Chemistry, University of Wisconsin, Madison, USA on "A local mode study of ring puckering effects in the infrared spectra of cyclopentane"

29 Nov 2023
Seminar Room # 350, second floor annex

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Speaker: Prof. Edwin L. Sibert III
Department of Chemistry, University of Wisconsin,
Madison, USA

Title: "A local mode study of ring puckering effects in the
infrared spectra of cyclopentane".

Day and Date: Wednesday, November 29, 2023

Time: 16.00 hrs.

Venue: Seminar room, room no. 350,
Chemistry Department (second floor)
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Hosted by Prof. Amber Jain

Talk Title : "A local mode study of ring puckering effects in the infrared spectra of cyclopentane".
Abstract
Ring flipping is a well-known phenomenon in organic chemistry in which the axial and equatorial positions of ring substituents are switched as a molecule interconverts between two chair-like structures. In cyclohexane this flip leads to energetically equivalent structures but with the axial and equatorial CH bonds interchanged. In cyclopentane one finds CH bond environments like those of the axial and equatorial positions of cyclohexane but here interchange occurs via a near barrierless motion known as pseudorotation. Kilpatrick, Pitzer and Spitzer realized in 1947 that this motion could be modeled as a particle in a ring and, as such, has important thermodynamical consequences due to the low frequency of the ring motion. Our combined experimental/theoretical study shows how the extent of the changing CH stretch and CH_2 bend environments upon pseudorotation is encoded in the infrared spectra corresponding to these vibrations. Our conclusions are supported by carefully comparing the experimental spectra to theoretical predictions of quantum mechanical model we have developed.