1. CHIRPED-PULSE FOURIER TRANSFORM MICROWAVE SPECTROSCOPY OF
RE12
CHIRPED-PULSE FOURIER TRANSFORM MICROWAVE SPECTROSCOPY OF
2-CHLORO-3-FLUOROPYRIDINE AND
2-CHLORO-6-FLUOROPYRIDINE
Sean Arnold, J. Chase Chewning & Gordon Brown
Department of Science and Mathematics, Coker College, Hartsville, SC, USA

2. Purpose:
Measure and assign the rotational spectra of 2-Cl-3-F-Pyridine and 2-Cl-6-F-Pyridine
Instrumentation test:
Is our chirped-pulse spectrometer capable of dealing with two nuclear quadrupoles?
2-chloro-3-fluoropyridine
2-chloro-6-fluoropyridine

3. Spectrometer Diagram
240 MHz

4. 250 MHz Chirped Pulse:

5. Chirped-Pulse Microwave Spectrometer

6. CP-FTMW Resolution Low-Res 20 μs FID Peak Width ~130 kHz (FWHM)
Doppler Splitting ~ 70. kHz
Hi-Res

7. Experimental: 2-Cl-3-F-Pyridine
Frequency (MHz)
10,000 signal averages (approximately 40 hours of measurement time)
100 μs FID
50 psi backing pressure (He/Ne mix)
Sample evaporated at room temperature

8. Experimental 2-Cl-6-F-Pyridine
Frequency (MHz)
10,000 signal averages (approximately 40 hours of measurement time)
100 μs FID
50 psi backing pressure (He/Ne mix)
Sample heated in nozzle to ~80° C

9. 2-Cl-3-F-Pyridine Assignments

10. 2-Cl-3-F-Pyridine Assignments

11. 2-Cl-6-F-Pyridine Assignments

12. Rotational Parameters for 2-chloro-3-fluoropyridine
2-chloro-3-fluoropyridine (35Cl)
2-chloro-3-fluoropyridine (37Cl)
B3LYP/ 6‑311++g(d,p)
Experimental
A (MHz)
(38)
(13)
B (MHz)
(87)
(12)
C (MHz)
(11)
(17)
DJ (kHz)
0.049
0.035 (13)
0.048
0.038 (16)
3/2 Χaa N(MHz)
0.745
0.554 (66)
0.45 (12)
¼ Χbb – Χcc N(MHz)
-1.680
(19)
(41)
3/2 Χaa Cl(MHz)
(58)
(21)
¼ Χbb – Χcc Cl(MHz)
2.805
2.276 (18)
2.2729
1.924 (78)
Number of Assigned Lines
N/A
317
155
OMC (MHz)
0.0090
0.0235
Δ (amu*A2)
0.062
-1.11

13. Rotational Parameters for 2-chloro-6-fluoropyridine
2-chloro-6-fluoropyridine (35Cl)
2-chloro-6-fluoropyridine (37Cl)
B3LYP/ 6‑311++g(d,p)
Experimental
A (MHz)
(15)
(21)
B (MHz)
(17)
(17)
C (MHz)
(13)
(61)
DJ (kHz)
0.0371
0.027 (19) -
3/2 Χaa N (MHz)
2.166 (99)
2.70
2.51 (13)
¼ (Χbb – Χcc)
N (MHz)
(17)
-1.697
(21)
Χab N (MHz)
-1.56
-1.45 (85)
3/2 Χaa Cl(MHz)
(12)
(18)
¼ Χbb – Χcc Cl(MHz)
(19)
(26)
Χab Cl (MHz)
-33.48
(49)
-25.8
-26.8 (20)
Number of Assigned Lines
N/A
153
111
OMC (MHz)
0.0217
Δ (amu*A2)
0.0592
0.0607

14. Conclusions: Measured 8-18.5 GHz spectra of the two molecules
Determined experimental rotational and quadrupole coupling constants
Successfully measured and analyzed compounds with two nuclear quadrupoles
2-chloro-3-fluoropyridine
2-chloro-6-fluoropyridine

15. Acknowledgements National Science Foundation (CHE-1213560)
American Chemical Society-Petroleum Research Fund (PRF #50746-UN16)
South Carolina EPSCoR/IDeA GEAR:RE Program
Coker College
Sean Arnold
Chase Chewning