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)
http://www.novelcs.com/Chirality.html
http://www.mcescher.com/
An Example
OH
O
O
R-naproxen
OH
O
O
S-naproxen
Diastereomers?
OH
O
HO
O
O
O
S-naproxen
R-naproxen
Alvarez-Valtierra, L. (2008) University of Pittsburgh. School of Arts and Science
Low Resolution Spectrum
IB
OH
O
O
IR
Wavenumbers
Chem. Phys. Lett. (2003), 375, pg634
Experimental Setup
To Beam Machine (BM)
Red Conformer of S-Naproxen
S-Naproxen
30586.06 cm-1
30584.35 cm-1
0.08 cm-1
Red Conformer of R-Naproxen
R-Naproxen
30584.35 cm-1
30585.98 cm-1
0.08 cm-1
Right Vs. Left
S-Naproxen
R-Naproxen
0.08 cm-1
0.08 cm-1
Red Conformer Inertial Parameters
S-Naproxen
(Red)
R-Naproxen
(Red)
A” (MHz)
1241.59 (6)
1241.56 (5)
B” (MHz)
214.70 (3)
214.73 (3)
C” (MHz)
202.15 (3)
202.16 (3)
∆I” (amu Ǻ2)
-260.8 (4)
-260.7 (4)
A’ (MHz)
1217.62 (5)
1217.59 (5)
B’ (MHz)
215.49 (3)
215.50 (3)
C’ (MHz)
202.44 (2)
202.46 (2)
∆I” (amu Ǻ2)
-263.8 (4)
-263.9 (4)
a/b/c-character
8.3/87.6/4.2
7.8/88.7/3.5
Band origin (cm-1)
30585.2
30585.2
OMC (MHz)
2.91
2.88
Temp (K)
3.0
3.0
S0
S1
R-Naproxen Blue Conformer
R-Naproxen
30686.50 cm-1
30687.96 cm-1
0.08 cm-1
S-Naproxen Blue Conformer
S-Naproxen
30686.50 cm-1
30687.96 cm-1
0.08 cm-1
Right Vs. Left
R-Naproxen
S-Naproxen
0.08 cm1
0.08
cm-1
Blue Conformer Inertial Parameters
S-Naproxen
(Blue)
R-Naproxen
(Blue)
A” (MHz)
1315.80 (6)
1315.71 (7)
B” (MHz)
205.36 (3)
205.30 (3)
C” (MHz)
196.10 (3)
196.07 (3)
∆I” (amu A2)
-267.9 (5)
-267.9(5)
A’ (MHz)
1304.20 (5)
1304.10 (7)
B’ (MHz)
204.90 (3)
204.87 (4)
C’ (MHz)
195.46 (3)
195.45 (3)
∆I” (amu Ǻ2)
-268.4 (5)
-268.9 (6)
a/b/c-character
5.6/84.7/0.7
5.6/84.7/0.7
Band origin (cm-1)
30687.2
30687.2
OMC (MHz)
3.32
3.91
Temp (K)
3.0
3.0
S0
S1
Possible R-Conformations
R-Naproxen I
R-Naproxen IV
MP2 / 6-31G**
R-Naproxen II
R-Naproxen V
R-Naproxen III
R-Naproxen VI
Conformation Determination
Experimental
Red Blue
Theory
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
Experimental vs. Theoretical
Results
Theoretical
Results
(MP2 / 6-31G**)
S-Naproxen
(Naproxen I)
R-Naproxen
(Naproxen I)
S-Naproxen
(Naproxen II)
R-Naproxen
(Naproxen II)
A” (MHz)
1315.0
1314.9
1240.5
1240.6
B” (MHz)
205.7
205.7
215.7
215.7
C” (MHz)
195.7
195.7
202.1
202.1
∆I” (amu A2)
-258.8
-258.8
-249.7
-249.7
Experimental
Results
S-Naproxen
(Blue)
R-Naproxen
(Blue)
S-Naproxen
(Red)
S-Naproxen
(Red)
A” (MHz)
1315.80 (6)
1315.71 (7)
1241.59 (6)
1241.56 (5)
B” (MHz)
205.36 (3)
205.30 (3)
214.70 (3)
214.73 (3)
C” (MHz)
196.10 (3)
196.07 (3)
202.15 (3)
202.16 (3)
∆I” (amu Ǻ2)
-267.9 (5)
-267.9(5)
-260.8 (4)
-260.7 (4)
S0
S0
MP2 / 6-31G**
Lowest Energy Conformations
S-naproxen II
S-naproxen I
MP2 / 6-31G**
R-naproxen II
R-naproxen I
Chem. Phys. Lett. (2003), 375, pg634
c
c
b
b
a
a
S-naproxen II
R-naproxen II
c
c
a
a
b
S-naproxen I
b
R-naproxen I
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 Snaproxen have matching spectra and
inertial parameters
Future work
Chiral axis
Chiral center
Diastereomers
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-0615755)