1. Structural Analysis of 2-Fluorophenol and 3-Fluorophenol Based on FTMW Rotational Spectra
Aimee Bell, Omar Mahassneh, James Singer,
Durell Desmond, Jennifer van Wijngaarden
Department of Chemistry, University of Manitoba
MI04
ISMS 71st Meeting
June 20, 2016

2. Fluorinated Compounds
Fluorinated compounds are used in a variety of industrial applications
Fluorination can be used to manipulate chemical and physical properties
Figures:
Faslodex – breast cancer drug
Fluorine substituted liquid crystals – used in LCDs
Fluorine Substituted
Liquid Crystals2
Faslodex1
1S. Purser et al. Chem. Soc. Rev. 2008, 37,
2R. Berger et al. Chem. Soc. Rev. 2011, 40,

3. Interactions Involving Fluorine
FTMW techniques allow for H-F interactions to be studied in isolation
Intermolecular interactions well documented with FTMW; intramolecular interactions not widely studied
-intramolecular interactions more commonly studied with IR
Intermolecular Interaction in CH3F•CHF33
Intramolecular Interaction in 2,3,5,6-tetrafluorohydroquinone4
3W. Caminati et al. Angew. Chem. Int. Ed. 2005, 44,
4A. Kovacs et al. Chem. Phys. 2007, 335,

4. Ecis - Etrans = -2.9 kcal/mol5
2-Fluorophenol
Cis-2-FPh
Trans-2-FPh
-cis stabilized by intramolecular interaction (OH---F)
Ecis - Etrans = -2.9 kcal/mol5
5MP2/aug-cc-pVDZ value from M.A. Moreira et al. J. Mol. Struct. 2012, 1009,

5. Ecis - Etrans = 0.2 kcal/mol5
3-Fluorophenol
Cis-3-FPh
Trans-3-FPh
-neither conformer has an intramolecular interaction
Ecis - Etrans = 0.2 kcal/mol5
5MP2/aug-cc-pVDZ value from M.A. Moreira et al. J. Mol. Struct. 2012, 1009,

6. Previous MW Studies of FPh
MW spectrum of cis-2-FPh
A. Dutta et al., J. Mol. Spec. 1985, 114,
MW spectrum of 3-FPh
A.I. Jaman et al., J. Mol. Spec , 86,
A.I. Jaman et al., J. Mol. Struct , 82,
A. Dutta, A.I. Jaman, Pramana , 24,
A.I. Jaman J. Mol. Spec. 2007, 245,
Proposed r0 Structure of Trans-3-FPh (1982)

7. Instrumentation
Sample Mixing Manifold
Microwave Circuit
Microwave Source
Vacuum Chamber
Balle-Flygare FTMW Spectrometer at the University of Manitoba6
6G. Sedo, J. van Wijngaarden, J. Phys. Chem. 2009, 131,

8. Experimental Conditions
Spectral range: 6 to 26 GHz
13C isotopologues observed in natural abundance
~1 bar of Ar bubbled through heated liquid samples
-samples had high boiling points ( C for 2FPh, 178 C for 3FPh)
-glass vessels were heated in a bath to raise the vapour pressure
Glass Bubbler Vessel in a Heated Bath

9. 2-Fluorophenol Dipole Moments
MP2/ G(2d,2p) a
Cis-2-FPh
μa = 1.17 D, μb = 0.45 D
Parent and 13C isotopologues detected
Trans-2-FPh
μa = D, μb = D
Not detected b μ b μ
-trans-2-FPh was not detected; too high energy for observation a

10. 2-Fluorophenol Spectroscopic Constants
Parent
13C1
13C2
13C3
13C4
13C5
13C6
Rotational Constants/MHz A
(11)
(44)
(44)
(45)
(44)
(44)
(43) B
(95)
(53)
(53)
(53)
(53)
(53)
(53) C
(69)
(35)
(35)
(39)
(35)
(35)
(35)
Centrifugal Distortion Constants/kHz ΔJ
0.0819(15)
0.0819
ΔJK
0.0546(41)
0.0546 ΔK
0.6050(48)
0.6050 δJ
(68) δK
0.1074(28)
0.1074
RMS/kHz
1.2
0.63
0.88
0.64
1.7
1.4
# of lines 79 16 15
Δ/amu•Å2
0.0018(4)
0.0016(3)
0.0015(3)
0.0018(3)
0.0020(3)
0.0021(3)
0.0019(3)
*Watson’s A-reduced Hamiltonian Ir Representation in Pickett’s SPFIT

11. 3-Fluorophenol Dipole Moments
MP2/ G(2d,2p) a a
Cis-3-FPh
μa = 0.73 D, μb = 0.13 D
Parent detected
Trans-3-FPh
μa = 2.07 D, μb = 2.29 D
Parent and 13C isotopologues detected b μ μ b

12. Sample Transitions of 3-Fluorophenol
Cis
S/N = 25
Cycles = 310
Trans
S/N = 25
Cycles = 115
-cis has weaker signal due to smaller dipole and higher energy

13. 3-Fluorophenol Spectroscopic Constants
Trans Conformer
Parent
13C1
13C2
13C3
13C4
13C5
13C6
Cis Conformer
Rotational Constants /MHz A
(29)
(12)
(18)
(11)
(16)
(17)
(16)
(45) B
(15)
(37)
(60)
(38)
(42)
(56)
(66)
(54) C
(12)
(18)
(29)
(17)
(20)
(20)
(28)
(34)
Centrifugal Distortion Constants /kHz ΔJ
(11)
(39)
ΔJK
(40)
(16) ΔK
0.6154(10)
0.6154
0.491(93) δJ
(55)
(21) δK
(55)
0.1260(84)
RMS/kHz
0.484
0.919
1.379
0.797
1.007
0.893
1.241
0.380
# of lines
154 44 41 39 40 36 37 47
Δ/amu•Å2
(9)
-0.017(2)
-0.018(3)
-0.015(2)
-0.017(3)
-0.019(3)
*Watson’s A-reduced Hamiltonian Ir Representation in Pickett’s SPFIT

14. Cis-2-FPh Aromatic Ring Geometry
Bond Lengths
Angles 1 2 3 4 5 6
C1-C2
δre = Å
δr0 = (2) Å
C2-C3
δre = Å
δr0 = (3) Å
C3-C4
δre = Å
δr0 = 0.001(3) Å
C4-C5
δre = Å
δr0 = 0.006(4) Å
C5-C6
δre = Å
δr0 = 0.002(3) Å
C6-C1
δr0 = (3) Å
C1-C2-C3
δre = 2.9o
δr0 = 3.1(3)o
C2-C3-C4
δre = -1.8o
δr0 = -1.9(4)o
C3-C4-C5
δre = 0.5o
δr0 = 0.3(4)o
C4-C5-C6
δre = 0.0o
δr0 = 0.1(3)o
C5-C6-C1
δre = 0.4o
C6-C1-C2
δre = -1.9o
δr0 = -1.6(3)o
re = eqm structures from Gaussian (MP2), r0 = ground state effective structures from STRFIT
-C1-C2 not shortened since both atoms are bonded to electronegative atoms (O and F)
δ = (Cis-2-FPh Value) – (Phenol re Value)

15. Trans-3-FPh Aromatic Ring Geometry
Bond Lengths
Angles
C1-C2
δre = Å
δr0 = 0.001(5) Å
C2-C3
δre = Å
δr0 = (5) Å
C3-C4
δre = Å
δr0 = (2) Å
C4-C5
δre = Å
δr0 = 0.003(3) Å
C5-C6
δre = Å
δr0 = (3) Å
C6-C1
δr0 = (2) Å
C6-C1-C2
δre = 0.3o
δr0 = 0.8(5)o
C1-C2-C3
δre = -1.5o
δr0 = -2.2(5)o
C2-C3-C4
δre = 2.5o
δr0 = 3.3(3)o
C3-C4-C5
δre = -1.7o
δr0 = -2.1(4)o
C4-C5-C6
δre = 0.6o
δr0 = 0.7(3)o
C5-C6-C1
δre = -0.2o
δr0 = -0.5(5)o 1 2 3 4 5 6
-deviations from phenol occur based on position of the F-atom
-electronegativity of F changes the hybridization character of nearby atoms
δ = (Cis-2-FPh Value) – (Phenol re Value)

16. Additional r0 Geometry 116.75(13)o 120.33(13)o 117.71(13)o 118.37(13)o
-<(C-C-F) angles also determined in r0 analysis
118.37(13)o

17. NBO Analysis of Cis-2-FPh
Fluorine lone pair donates to π* orbital of OH
Not seen in other isomers of fluorophenol
Analogous interaction in cis-2- cyanophenol: 0.72 kcal/mol7
-NBO = natural bond orbital (done with Gaussian)
-analysis done for all fluorophenols and phenol
-OH---F interaction energy: 0.73 kcal/mol (~3 kJ/mol)
Eint = 0.73 kcal/mol
MP2/ G(2d,2p)
7R. Conrad et al. Phys. Chem. Chem. Phys. 2010, 12,

18. Theoretically, Is There a Hydrogen Bond in Cis-2-FPh?
IUPAC Minimum Angle for X-H•••Y H-bond:
110o 8 (
2.212 Å
112.3o
van der Waals Radii Sum of H+F:
2.56 Å 9
MP2/ G(2d,2p)
8E. Arunan et al. Pure Appl. Chem. 2011, 83,
9R.S. Rowland, R. Taylor. J. Phys.Chem. 1996, 100,

19. Concurrent Work
2-FPh and 3-FPh rovibrational spectra observed in far-IR region
Out-of-plane OH torsion vibration being analyzed
Trans-2-FPh
344 cm-1
Cis-2-FPh
381 cm-1
Trans-3-FPh
311 cm-1
Cis-3-FPh
319 cm-1

20. Acknowledgements
Wenhao Sun

21. Effects of Electronegativity
-0.5
0.2
0.0
-0.4
Δ = 0.7
Δ = 0.4
Δ = 0.2 s p e- s
This explains why C2-C3 is shortened in cis-2-FPh and why C1-C2 is not.
-0.518
+0.518