1. The rotational spectra of 4,4,4-trifluorobutyric acid and its complex with Formic acid
Yoon Jeong Choi, Alex Treviño, Susanna L. Stephens, Stephen A. Cooke, Stewart E. Novick, Wei Lin
WD04 Clusters and Complexes Wednesday 21th June :21 – 09:36 AM

2. Chirp Pulse Experiment
Center Frequency, ν, between 8-18 GHz
Linear Frequency Sweep 0 – x - “Chirp”
ν +/- x is amplified, pulsed and broadcast
Excitation interacts with the molecules
Free Induction Decay Collected, Amplified and Digitized on a 40 GS/s oscilloscope
Chirp Pulse Experiment
G.S. Grubbs, C.T. Dewberry, K.C. Etchison, K.E. Kerr, S.A. Cooke;
Rev. Sci. Instrum., 78, (2007)
To Diff. Pump

3. Perfluoropropanoic acid
Trifluoroacetic acid
S. Antolinez, J.L. Alonso, H. Dreizler, E. Hentrop, D.H. Sutter; Z. Naturforsch. 54a, 524, (1999)
B. Ouyang, T.G. Starkey, B.J. Howard; J. Phys. Chem. A., 111, 6165 (2007)
Perfluoropropanoic acid
G.S. Grubbs II, A. Serrato III, D. A. Obenchain, S.A. Cooke, S.E. Novick, W. Lin; J. Mol. Spec., 275, 1(2012).
G.S. Grubbs II, D.A. Obenchain, D.S. Frank, S.E. Novick, S.A. Cooke, A. Serrato III, W. Lin; J. Phys. Chem. A., 119, (2015)
Perfluorobutyric acid
(& its monohydrate)
J. Thomas, A. Serrato III, W Lin, W. Jäger, Y. Xu; Chem. Eur. J., 20, 6148, (2014)
Perfluoropentanoic acid
A.M. Pejlovas, W. Lin, S.G. Kukolich; J. Chem. Phys., 143, (2015)
One lower energy conformer detected for perfluorocarboxylic acids
Difluoroacetic acid
B.P. van Eijck, A.A.J. Maagdenberg, G. Janssen, T.J. van Goethem-Wiersma;
J. Mol. Spec., 98, 282 (1983)
Fluoroacetic acid
B.P. van Eijck, P. Brandts, P.M. Maas; J. Mol. Strc., 44, 1 (1978)
B.P. van Eijck, G. Van der Plaats, P.H. Van Roon; J. Mol. Spec., 11, 67 (1971)
Two conformers detected for short partially fluorinated carboxylic acids

4. 3,3,3-trifluoro-2-(trifluoromethyl)propanoic acid
PES’ partially fluorinated carboxylic acids chains multiple conformers
3,3,3-trifluoro-2-(trifluoromethyl)propanoic acid
J. Thomas, M.J. Carrillo, A. Serrato III, E.G. Schnitzler, W. Jäger, Y. Xu, W. Lin; Chem. Phys. Lett., 661, 210 (2016)
Two lower energy conformers observed
2,3,3,3-tetrafluoropropanoic acid
Lin et al. Investigation ongoing
Three conformers observed
3,3,3-trifluoropropanoic acid
L. Evangelisti, J. van Wijngaarden; J. Mol. Spec., 290, 1 (2013)
One lower energy conformer observed

5. 4,4,4-Trifluorobutyric acid conformational landscape
Original B3LYP / aug-cc-pVTZ to expected major conformer
Dihedral τ(OO=C-C1-C2-C3) in 5° B3LYP / aug-cc-pVTZ
Minima structures further MP2 / aug-cc-pVTZ
Higher energy conformers with dihedrals of 124° and -124° C1 C2 C3 C4
Conformer I
Conformer II
0.48 kJ mol-1
Conformer I C1 C2 C3 C4

6. 4,4,4-Trifluorobutyric acid
Conformer 1 C1 C2 C3 C4
Conformer 2
Dimer?
6 ← 5
7 ← 6
8 ← 7
5 ← 4
9 ← 8
Frequency /MHz
Intensity /V
1.5 bar Ar bubbled through sample 7200 averages

7. 4,4,4-Trifluorobutyric acid Conformer 1
Dimer?
“New”
6 ← 5
7 ← 6
8 ← 7
5 ← 4
9 ← 8
Frequency /MHz
Intensity /V
1.5 bar Ar bubbled through sample 7200 averages

8. 4,4,4-Trifluorobutyric acid Conformer 2?
Experimental
Conformer 2:
Fit of 3 possible transitions, to be verified
Conformer 2:
Spectral prediction
Conformer 1:
Spectral Fit
Frequency /MHz
Conformer 1
Conformer 2
MP2 aug-TZ
Experiment
Speculation*
Bbar/MHz
728.9
724.5
743.75
743.12
*Preliminary results based on 3 transitions at 2:1 intensity

9. 4,4,4-Trifluorobutyric acid Spectroscopic constants
B3LYP/
aug-cc-pVTZ
MP2/
Experimental
A0 /MHz
3628.3
3640.3
(33)
B0 /MHz
739.15
751.87
(64)
C0 /MHz
694.90
706.02
(64)
J /kHz  -
0.0200(44)
JK /kHz
0.384(13)
Paa/(uǺ2)
635.86
624.57
628.99
Pbb/(uǺ2)
91.42
91.24
90.71
Pcc/(uǺ2)
47.88
47.59
47.79 N 33
/kHz 7
Planar moment of inertia: Paa = (Ib +Ic – Ia)/2, Pbb = (Ia +Ic – Ib)/2, and Pcc = (Ia +Ib - Ic)/2.
Watson Ir in Pickett

10. 4,4,4-Trifluorobutyric acid ··· formic acid
8-12 GHz
Two conformers
86 a-type transitions
No splitting's associated with hydrogen exchange
Frequency /MHz

11. 4,4,4-Trifluorobutyric acid ··· formic acid
Conformer A
Conformer B
4,4,4-Trifluorobutyric acid monomer conformers
Conformer 1
Conformer 2

12. 4,4,4-Trifluorobutyric acid-formic acid
Conformer A
Conformer B
B3LYP
MP2
Experimental
ΔD /kJ mol-1 -
4.0
ΔD0 /kJ mol-1
3.6
3.9
A0 /MHz
2523.1
2514.7
(17)
2666.4
2673.0
B0 /MHz
285.09
289.58
(12)
281.48
285.48
C0 /MHz
269.21
273.03
(12)
267.50
271.11
ΔJ /kHz
(22)
ΔJK /kHz
0.0380(17)
ΔK /kHz
120(52)
µa /D
1.7
µb /D
0.3
0.4
µc /D
0.0

13. Manifestation of proton tunneling
1/2
Formic acid dimer
O. Birer, M. Havenith; Annu. Rev. Phys. Chem., 60, 263 (2009) & refs.
Malonaldehyde
W.F. Rowe, R.W. Duerst, E.B. Wilson; J. Am. Chem. Soc., 98, 4021 (1976)
S.L. Baughcum, R.W. Duerst, W.F. Rowe, Z. Smith, E.B Wilson; J. Am. Chem. Soc., 103, 6296 (1981)
S.L. Baughcum, Z. Smith, E.B. Wilson, R.W. Duerst; J. Am. Chem. Soc., 106, 2260 (1984)
P. Turner, S.L. Baughcum, S. L. Coy, Z. Smith; J. Am. Chem. Soc. 106, 2265 (1984)
Tropolone
K. Tanaka, H. Honjo, T. Tanaka, H. Kohguchi, Y. Ohshima, Y. Endo; J. Chem. Phys., 110, 1969 (1999)
J.C. Keske, W. Lin, W.C. Pringle, S.E. Novick, T.A. Blake, D.F. Plusquellic; J. Chem. Phys., 124, (2006)
Propriolic acid ··· Formic Acid
A.M. Daly, P.R. Bunker, S.G. Kukolich; J. Chem. Phys., 132(20), /1 (2010)
A.M. Daly, P.R. Bunker, S.G. Kukolich; J. Chem. Phys., 133(7), /1 (2010)
A.M. Daly, K.O. Douglass, L.C. Sarkozy, J.L. Neill, M.T. Muckle, D.P. Zaleski, B.H. Pate, S.G. Kukolich; J. Chem. Phys., 135, /1 (2011)
Benzoic Acid ··· Formic Acid
L. Evangelisti, P. Ecija, E.J. Cocibero, F. Castano, A. Lessarri, W. Caminati, R. Meyer; J. Phys. Chem. Lett., 3, 3770 (2012)

14. Manifestation of proton tunneling
2/2
Formic acid ··· acetic acid
M.C.D. Tayler, B. Ouyang, B.J. Howard; J. Chem. Phys., 134, /1 (2011)
Acrylic acid ··· Trifluoroacetic acid
(cis & trans)
Q. Gou, G. Feng, L. Evangelisti, W. Caminati,;
J. Phys. Chem. A., 117, (2013)
Acrylic acid ··· Difluoroacetic acid
G. Feng, Q. Gou, L. Evangelisti, W. Caminati;
Angew. Chem. Int. Ed., 53, 530 (2014)
Perfluorobutyric acid ··· formic acid
J. Thomas, A. Serrato III, M.J. Carrillo, W. Lin, W. Jäger, Y. Xu; J. Mol. Spectrosc., 335, 88 (2017)
2.759 MHz
1.203 MHz
303
313
1.877 MHz
2.806 MHz
12 kHz
No Tunneling
No Tunneling

15. 4,4,4-Trifluorobutyric acid
PES landscape determined
One conformer observed
Analogous to 3,3,3-trifluoropropionic acid1
4,4,4-Trifluorobutyric acid-formic acid complex
No splittings associated with hydrogen exchange
Two conformers calculated
2nd conformer that would be formed by proton exchange not observed
First measurement
1 L. Evangelisti, J. van Wijngaarden; J. Mol. Spec., 290, 1 (2013)

16. National Science Foundation Wesleyan Chemistry Department FB02 WE10
Wei Lin
Stewart Novick
Steve Cooke
Karen Peterson
Pete Pringle
Wilman Orellana
Yoon Choi
Angela Chung
Eric Arsenault
Robert Melchreit
National Science Foundation
Wesleyan Chemistry Department
FB02
WE10
TI11
FB06
Not pictured:
Robert Melchreit TC02
Karen Peterson: RH07