ASSIGNMENT OF THE PERFLUOROPROPIONIC ACID-FORMIC ACID COMPLEX AND THE DIFFICULTIES OF INCLUDING HIGH Ka TRANSITIONS Daniel A. Obenchain, Eric A. Arsenault, Wei Lin, Stewart E. Novick, & S. A. Cooke

Perfluoropropionic Acid J. Mol. Spectrosc. 275 (2012) 1-4

Perfluoropropionic Acid Hydrates J. Chem. Phys A. 119 (2015) 10475-10480

Perfluoropropionic Acid Hydrates H2O-PFPA (H2O)2-PFPA

Spectra Collection 10k averages on a chirped broadband microwave spectrometer 7-13 GHz Additional measurements made on a cavity spectrometer 5.5-18 GHz Argon bubbled through the a mixture of perfluoropropionic acid and formic acid in a 1:1 volume ratio at 1.2 atm

Observed Spectra B+C is  800 MHz Observed well resolved a-type R-branch transitions from J=8 to J=14 in the broadband spectrum

Ka>2 Ka=0 Ka=2 Ka=2 Ka=1 J= 13-12 region 10,000 averages broadband Rough prediction based on initial fits Ka>2 Ka=0 Ka=2 Ka=2 Ka=1

Fit from only Ka=0,1 transitions Fits of the spectra Fit from only Ka=0,1 transitions A0 1524.1(27) MHz A1 1483.3(24) MHz B0 395.8059(19) MHz B1 395.7573(18) MHz C0 386.0053(14) MHz C1 385.9987(13) MHz DJ,0 0.0813(65) kHz DJ,1 0.0475(62) kHz N 20 rms 3.9 kHz No combination of transitions appears to produce quality fits that accurately predict new transitions Best fits so far include only Ka=0 and a few Ka=1 a-type transitions

Cavity Spectra 250 Averages 150 Averages Ka=3 MHz MHz

Cavity Spectra No additional splitting observed Now able to access J=5 to J=23 Only fits with Ka=0 are decent, loses predictability with higher Ka

Trifluoroacetic acid-formic acid

Perfluoroacetic acid-formic acid

Formic Acid-Acetic Acid complex Prof. Brian Howard’s group at Oxford tackled a double proton transfer problem Observed both double proton transfer, and methyl internal rotation Tayler, M. C. D., Ouyang, B., Howard, B. J., J. Chem. Phys. 134 (2011) 054316

Formic Acid-Acetic Acid complex Howard states that the fits were heavily dependent on 2nd order corrections to the Coriolis terms. So far, our attempts at including these terms have not produced quality fits. Tayler, M. C. D., Ouyang, B., Howard, B. J., J. Chem. Phys. 134 (2011) 054316

Ground State Dipole moment predictions a = 2.7 D b = 0.3 D c = 0.3 D Gaussian 09, using APF-D density function, with a 6-311++G(2d,2p) basis set

Ground State Gaussian 09, using APF-D density function, with a 6-311++G(2d,2p) basis set

Possible transition states Double proton transfer TS 1500 cm-1 above minimum

Possible transition states Acid rotation TS 400 cm-1 above minimum Same Structure, different views

Cause of the doubled spectrum No inversion of a, we are likely not observing cross-state a-type transitions We have made attempts at assignment of the enriched deuterium spectra, but no results have come of it as of yet

Internal Rotation of -CF3 group Splitting observed? Internal Rotation Proton Transfer Perfluoropropionic Acid No - Perfluoropropionic Acid-H2O Perfluoropropionic Acid-(H20)2 Perfluoropropionic Acid- Cyclopropanecarboxylic Acid Trifluoroacetic Acid Yes Yes (3rd excited state) Trifluoroacetic Acid-Formic Acid Trifluoroacetic Acid-H2O Yes (water inversion) Acetic Acid-Formic Acid Perfluoropropionic Acid-Formic Acid ?

Internal Rotation of -CF3 group

Suggestions? We welcome anyone with suggestions or comments with this problem to contact us “We hope the present method’s simplicity renews the inspiration to study, at high resolution, similarly large and ‘loose’ molecules where there is more than one large amplitude internal motion present” Tayler, M. C. D., Ouyang, B., Howard, B. J., J. Chem. Phys. 134 (2011) 054316

Acknowledgements Cluster at Wesleyan University funded NSF Grant # CNS-0619508 Prof. Wei Lin at University of Texas Rio Grande Valley Novick/Pringle/Cooke Groups

Internal Rotation of -CF3 group Splitting observed? Internal Rotation Proton Transfer Perfluoropropionic Acid J. Mol. Spectrosc. 275 (2012) 1-4 Perfluoropropionic Acid-H2O J. Chem. Phys A. 119 (2015) 10475-10480 Perfluoropropionic Acid-(H20)2 Perfluoropropionic Acid- Cyclopropanecarboxylic Acid S. Antolinex, H. Driezler, V. Storm, D. H. Sutter, J. L. Alonso. Z. Naturforsch. 52a, 803-806 (1997) Trifluoroacetic Acid J. Mol. Spectrosc. 113, 196-207 ( 1985) Trifluoroacetic Acid-Formic Acid Chem. Phys. 148 ( 1990) 129- 140 Trifluoroacetic Acid-H2O J. Phys. Chem. A 2007, 111, 6165-6175 Acetic Acid-Formic Acid Tayler, M. C. D., Ouyang, B., Howard, B. J., J. Chem. Phys. 134 (2011) 054316 Perfluoropropionic Acid-Formic Acid This work