Beyond the Bend: Exploring the Conformational Landscape of Decyl, Undecyl, and Dodecylbenzene Daniel M. Hewett, Simply John T. Lawler, and Timothy S. Zwier Department of Chemistry, Purdue University Funding: DOE Basic Energy Sciences Combustion Program Funding

Motivations ? ? Nils O. B. Lüttschwager, Tobias N. Wassermann, Ricardo A. Mata, Martin A. Suhm The Last Globally Stable Extended Alkane Angew. Chem. Int. Ed. 52 (2013) 463-466 I would remove the reference to soot formation. It’s too subtle a connection to make. Identifying the First Folded Alkylbenzene via Ultraviolet, Infrared, and Raman Spectroscopy of Pentylbenzene through Decylbenzene Daniel M. Hewett, Sebastian Bocklitz, Daniel P. Tabor, Edwin L. Sibert III,* Martin A. Suhm, and Timothy S. Zwier

Fluorescence Excitation and Dispersed Fluorescence Chamber 7/20/2018 Fluorescence Excitation and Dispersed Fluorescence Chamber Detect total fluorescence UV laser tuned Conformer A (S0, ZPL) A*(S1)

Ground State Methods LIF S0-FDIRS Tune UV Laser Collect Total Fluorescence Collect Total Fluorescence Fix UV Laser Add in a couple of words: on LIF: ‘Tune UV laser’ and ‘Collect total fluorescence’ On S0 FDIRS: Tune IR and ‘Fix UV on conformer origin’ Tune IR Laser LIF S0-FDIRS

Octylbenzene: g1g3g4 g=gauche defect in the chain Eureka! Look at all that structure! no more lumps, theory predicts three major bands in middle region, gets the 2950 band from the double gauche, additional activity in low region g=gauche defect in the chain

Folded vs. Extended Octylbenzene Folded All Trans Eureka! Look at all that structure! no more lumps, theory predicts three major bands in middle region, gets the 2950 band from the double gauche, additional activity in low region Octylbenzene Folded All Trans

UV Spectra: S0-S1 origin region

Energy Level Diagrams all trans all trans Octylbenzene Decylbenzene

UV Spectra: S0-S1 origin region Add relative scale from the all trans

Decylbenzene IR Spectra * * * *

Decylbenzene IR Spectra g1g2g4g5 = 0.10 kJ/mol g1g’4g’5 = 1.31 kJ/mol

Decylbenzene IR Spectra g1g2g4g5 = 0.10 kJ/mol g1g’4g’5 = 1.31 kJ/mol

Undecylbenzene IR Spectra * * * *

Dodecylbenzene IR Spectra * * *

Future Work Diaryls Where’s the stack?

Conclusions Observed rapid increase in folded conformer population as chain length increases Alkyl CH stretch region becoming very difficult to use as a spectroscopic tool as chain length increases

Acknowledgements Dr. Tim Zwier Simply John T. Lawler The Zwier group DOE