1. STUDYING THE STEREOCHEMISTRY OF NAPROXEN USING ROTATIONALLY RESOLVED ELECTRONIC SPECTROSCOPY
Justin Young, Leonardo Alvarez-Valtierra
and David W. Pratt.
University of Pittsburgh
Science(2006), vol. 323, pg. 237(4)

2. An Example
R-naproxen
S-naproxen

3. Diastereomers? S-naproxen R-naproxen
Alvarez-Valtierra, L. (2008) University of Pittsburgh. School of Arts and Science

4. Low Resolution SpectrumIB IR
Wavenumbers
Chem. Phys. Lett. (2003), 375, pg634

5. Experimental Setup
To Beam Machine (BM)

6. Red Conformer of S-Naproxen
cm-1
cm-1
0.08 cm-1
S-Naproxen

7. Red Conformer of R-Naproxen
cm-1
cm-1
0.08 cm-1
R-Naproxen

8. Right Vs. Left
S-Naproxen
R-Naproxen
0.08 cm-1
0.08 cm-1

9. Red Conformer Inertial Parameters
S-Naproxen
(Red)
R-Naproxen S0
A” (MHz)
(6)
(5)
B” (MHz)
(3)
(3)
C” (MHz)
(3)
(3)
∆I” (amu Ǻ2)
(4)
(4) S1
A’ (MHz)
(5)
(5)
B’ (MHz)
(3)
(3)
C’ (MHz)
(2)
(2)
(4)
(4)
a/b/c-character
8.3/87.6/4.2
7.8/88.7/3.5
Band origin (cm-1)
OMC (MHz)
2.91
2.88
Temp (K)
3.0

10. R-Naproxen Blue Conformer
cm-1
cm-1
0.08 cm-1
R-Naproxen

11. S-Naproxen Blue Conformer
cm-1
cm-1
0.08 cm-1
S-Naproxen

12. Right Vs. Left
R-Naproxen
S-Naproxen
0.08 cm-1
0.08 cm-1

13. Blue Conformer Inertial Parameters
S-Naproxen
(Blue)
R-Naproxen S0
A” (MHz)
(6)
(7)
B” (MHz)
(3)
(3)
C” (MHz)
(3)
(3)
∆I” (amu A2)
(5)
-267.9(5) S1
A’ (MHz)
(5)
(7)
B’ (MHz)
(3)
(4)
C’ (MHz)
(3)
(3)
∆I” (amu Ǻ2)
(5)
(6)
a/b/c-character
5.6/84.7/0.7
Band origin (cm-1)
OMC (MHz)
3.32
3.91
Temp (K)
3.0

14. Possible R-Conformations
R-Naproxen I
R-Naproxen II
R-Naproxen III
R-Naproxen IV
R-Naproxen V
R-Naproxen VI
MP2 / 6-31G**

15. Conformation Determination
Experimental
Theory
Red
Blue I II
III IV V VI A”
1241.5
1315.7
1314.9
1240.6
1447.6
1254.8
1274.0
1226.7 B”
214.7
205.3
205.7
215.7
198.1
214.1
214.2
213.6 C”
202.2
196.07
195.7
202.1
191.4
200.6
197.2
199.7
MP2 / 6-31G**
R-naproxen II
R-naproxen I

16. Experimental vs. Theoretical Results
(MP2 / 6-31G**)
S-Naproxen
(Naproxen I)
R-Naproxen
(Naproxen II) S0
A” (MHz)
1315.0
1314.9
1240.5
1240.6
B” (MHz)
205.7
215.7
C” (MHz)
195.7
202.1
∆I” (amu A2)
-258.8
-249.7
Experimental
(Blue)
(Red)
A” (MHz)
(6)
(7)
(6)
(5)
(3)
(3)
(3)
(3)
(3)
(3)
(3)
(3)
∆I” (amu Ǻ2)
(5)
-267.9(5)
(4)
(4)
MP2 / 6-31G**

17. Lowest Energy Conformations
S-naproxen II
R-naproxen II
S-naproxen I
R-naproxen I
Chem. Phys. Lett. (2003), 375, pg634
MP2 / 6-31G**

18. c c b b a a
S-naproxen II
R-naproxen II c c a a b b
R-naproxen I
S-naproxen I

19. Summary
Rotationally resolved electronic spectra of R- and S-naproxen were obtained.
For each enantiomer two conformations were assigned.
As expected the conformations R and S-naproxen have matching spectra and inertial parameters

20. Future work
Chiral axis
Chiral center
Diastereomers

21. Acknowledgments
Leonardo Alvarez, Ryan Bird, Casey Clements, Adam Fleisher, Philip Morgan and Jessica Thomas
Professor David W. Pratt for his encouragement and continuing support
Funding by the National Science Foundation (CHE )