The CP-FTMW Spectrum of Verbenone Frank E. Marshalla, Galen Sedob, Channing Westc, Brooks H. Patec, Stephanie M. Allpressd, Corey J. Evansd, Peter D. Godfreye, Don McNaughtone, G. S. Grubbs IIa aMissouri University of Science and Technology bUniversity of Virginia’s College at Wise cUniversity of Virginia dUniversity of Leicester eMonash University

Motivation Verbenone is chiral Verbenone is a monoterpene 1 Motivation Verbenone is chiral Good candidate for determining enantiomeric excess (EE) through chiral tagging (insert chiral tagging talk reference) Determining EE Requires a very thorough understanding of the molecule Verbenone is a monoterpene Recent studies of terpenoids show splittings that arise from various molecular motions Our goal is to determine if any of these motions are present in this system 1By Edgar181 - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2427880

Missouri S&T CP-FTMW 6-18 GHz linear frequency sweep (“chirp”) Expandable to 2-18 GHz with a specific amplifier 4us, 6GHz chirps Low noise, High fidelity instrument Minimal number of parts AWG and Oscilloscope eliminate multiple circuit components 23GHz, 100GS/s oscilloscope 40W Solid state power amplifier 50GS/s digitization rate, 20GHz bandwidth AWG Insert ArHCl spectra.

Verbenone – Missouri S&T CP-FTMW >93% (1S)-(-)-Verbenone purchased from Sigma Aldrich Liquid sample was placed in a U shaped tube and heated to 80C approximately 1 meter from the nozzle 6-10 psig of Argon gas was bubbled through the sample Pulsed into the chamber at 1 Hz. Data collected at 5 FIDs per gas pulse from 6-18 GHz 1 million averages collected

Verbenone – University of Virginia CP-FTMW2 >93% (1S)-(-)-Verbenone purchased from Sigma Aldrich Liquid sample was heated to 65 C in a heated nozzle 4 nozzles were utilized 10 psig of Neon backing gas was used Data collected from 2-8 GHz 1 million averages collected 2J. L. Neill, S. T. Shipman, L. Alvarez-Valtierra, A. Lesarri, Z. Kisiel, B. H. Pate, J. Mol. Spectrosc. 269 (2011) 21

Verbenone - Monash Free jet Stark-modulated spectrometer3 >93% (1S)-(-)-Verbenone purchased from Sigma Aldrich Sample heated to 80C Jet stream of 30 kPa of Argon was used 48-72 GHz frequeny range 3D. McNaughton, P. D. Godfrey, J.-U. Grabow, J. Mol. Spectrosc. 274 (2012) 1

Quantum Chemical Calculations Geometry Optimizations in Gaussian09 B3LYP D3BJ with a def2-TZVP basis set A more in depth paper is in the works from Pate and coworkers

Analysis b type R branch spectra primarily observed a, c type R branch transitions were observed with weaker intensity 633 transitions assigned for parent between 2-69 GHz 1250 total transitions across 12 isotopologues Only parent transitions were observed above 8 GHz Weaker isotopologues were observed in natural abundance for each heavy atom No splittings observed

Atoms 2,4,6,25 off axis -> more transitions Atoms 2,4,6,25 off axis -> more transitions. O (25) only has 25, but is 5x less abundant. 5*25 = 125 transitions. Planar atoms have about the same # of transitions. Parent transitions include stark spectrometer, which has much higher uncertainty. Monash transitions allowed for determination of constants below d2.

Discussion Important to determine complete experimental structure for chiral tagging Observed structures were in excellent agreement with theoretical structures Theoretical vs. Experimental errors were -0.41%, -0.32%, and -0.31% for A, B, C respectively re structure for theory and experiment were determined to be virtually identical Important to accurately calculate theoretical structures for Chiral Tagging

Conclusion CP-FTMW spectrum of (1S)-(-)-Verbenone has been reported Substitution structure was derived Theoretical substitution structure was in excellent agreement with experimental structure No splittings due to internal motion were observed

Acknowledgements Dr. Garry Grubbs and Missouri S&T Lab members Galen Sedo, Brooks Pate, Galen Sedo, Channing West, Brooks H. Pate, Stephanie M. Allpress, Corey J. Evans, Peter D. Godfrey, Don McNaughto University of Missouri Research Board Grant Uva-Wise Faculty Development Committee NSF MRI Award 1531913 Pictures of Galen, Brooks, Corey Evans