1. Department of Chemistry *Department of Chemistry, Mt. Holyoke College,
Determination of the Structure of Cyclopenteneoxide and the Argon Cyclopenteneoxide van der Waals Complex
Andrea J. Minei, Jennifer van Wijngaarden*,
Wallace C. Pringle, and Stewart E. Novick
Department of Chemistry
Wesleyan University
Middletown, CT 06459
*Department of Chemistry, Mt. Holyoke College,
South Hadley, MA 01075

2. van der Waals Complexes
vdW complex a* b* c*
Argon Methylene Cyclobutane
0.11
0.51
+3.62
Argon Cyclobutanone1
0.23
0.55
±3.48
Argon Thietane
0.57
-3.79
Argon Oxetane2
0.67
0.14
±3.5
Argon Chlorocyclobutane3
1.27
2.82
-2.52
Argon Cyclopentanone
0.95
0.80
±3.46
Neon Cyclopentanone
0.91
0.78
±3.26
1Munrow, M.R.;Pringle, W.C.; Novick, S.E.; J. Phys. Chem. A 103, (1999)
2 Lorenzo, F.; Lessari, A.; Lopez, J.C.; Alonso, J.L.; Chemical Physics Letters 286(3,4), (1998)
3 Subramanian, R; Szarko, J.M.; Pringle, W.C.; Novick, S.E.; J. Mol. Struct. 742(1-3) (2005)
* On the PAS of the parent molecule upon complexation with Argon or Neon

3. van der Waals Complexes
Argon Methylene Cyclobutane
Argon Cyclopentanone

4. Cyclopenteneoxide a b c a

5. Cyclopenteneoxide Experimental Conditions
0.5% Cyclopenteneoxide in Argon
~2 atm backing pressure
5-20 GHz range
Isotopomers observed in natural abundance

6. Cyclopentenoxide Results
25 a-type transitions
21 c-type transitions a b

7. Spectroscopic Constants for Cyclopenteneoxide
W. J. Lafferty
12C5H8O
α-13C
ββ’-13C
γγ’-13C
18O
A (MHz)
(9)
(5)
(1)
(3)
(9)
B (MHz)
(9)
(2)
(4)
(1)
(5)
C (MHz)
(8)
(2)
(3)
(9)
(4)
ΔJ (kHz)
0.86(4)
0.86*
ΔJK (kHz)
0.71(2)
0.71*
ΔK (kHz)
1.03(2)
1.03*
δJ (kHz)
0.150(5)
0.150*
δK (kHz)
0.31(2)
0.31* N 24 46 6 7
σ (kHz) 5 1
* Fixed to the all 12C parent isotopomer

8. Cyclopenteneoxide Improved all 12C rotational constants
Determined the 5 quartic centrifugal distortion constants
Three 13C isotopomers
18O isotopomer
Complete heavy atom substitution structure
Accurate starting structure for the Argon complex investigation

9. Argon Cyclopenteneoxide Experimental Conditions
0.5% Cyclopenteneoxide in Argon gas
~2 atm backing pressure
5-20 GHz range
Possible complex lines tested against Neon
Isotopomers observed in natural abundance
Our experimental conditions for the argon complex were roughly the same for that of cyclopenteneoxide itself
The only difference was that for any candidate for the argon complex, we tested these transition against a tank of cyclopenteneoxide in neon gas to help confirm that these transitions were indeed for the argon complex

10. vdW Complex Results 130 frequencies observed and fit
75 strong a-type transitions
55 weak b-type transitions b

11. Where is Argon? a = | 0.27 | Å b = | 0.42 | Å c = | 3.91 | Å
Position of Argon in the Principal Axis System (PAS) of Cyclopenteneoxide
a = | 0.27 | Å
b = | 0.42 | Å
c = | 3.91 | Å

12. Spectroscopic Constants for the Argon Cyclopenteneoxide Complex
Ar-12C5H8O
Ar-α13C
Ar-ββ’13C
Ar-γγ’13C
A (MHz)
(5)
(6) 
(6)
(1)
B (MHz)
(2)
  (5)
(6)
(3)
C (MHz)
(2)
  (5)
(7)
(3)
ΔJ (kHz)
2.2319(9)
2.201(4)
2.214(5)
2.2218(3)
ΔJK (kHz)
14.82(1)
14.82*
ΔK (kHz)
16.15(4)
16.15*
δJ (kHz)
0.0940(5)
0.0940*
δK (kHz)
4.90(9)
4.90*
ΦJJK (kHz)
(9) *
ΦJKK (kHz)
(3) * N
130
16  23 29
σ (kHz) 4  5 5
* Fixed to the all 12C parent isotopomer

13. Signs of rs Position of Argon
Structure of complex in PAS of the monomer
α-12C position has same Kraitchman coordinates as only one of the four α-13C positions
Argon position determined c
α13C a b

14. Argon is Below Oxygen! a = 0.27Å, b = 0.42Å, c = -3.91Å
Position of Argon in the Principal Axis System (PAS) of Cyclopenteneoxide
a = 0.27Å, b = 0.42Å, c = -3.91Å c a a a b

15. Argon Coordinates in the PAS of Cyclopenteneoxide
a (Å)
b (Å)
c (Å) rs
0.27
0.42
-3.91 r0
0.42 
0.56
-3.88 
rm(1)
0.18 
0.00
-3.93 
* r0 and Watson’s rm(1) calculations courtesy of Professor
Zbigniew Kisiel’s programs STRFIT and PMIFST, available at   

16. Wide Amplitude Cross Ring Motion

17. van der Waals Complexes
 vdW complex a* b* c*
Argon Methylene Cyclobutane
0.11
0.51
+3.62
Argon Cyclobutanone
0.23
0.55
±3.48
Argon Thietane
0.57
-3.79
Argon Oxetane
0.67
0.14
±3.5
Argon Chlorocyclobutane
1.27
2.82
-2.52
Argon Cyclopentanone
0.95
0.80
±3.46
Neon Cyclopentanone
0.91
0.78
±3.26
Argon Cyclopenteneoxide
 0.27
0.42
-3.91
* Position of rare gas in the principal axis system of each individual molecule

18. rs Position of Argon X X: b b b b Equivalent 13C spectra for
C=CH Å
C=O 0.55 Å
S Å
O Å b
2.70 Å X b b b
0.80 Å b
0.42 Å
Equivalent 13C spectra for
isotopomers of the complex
Unique 13C spectra for each isotopomer of the complex

19. Conclusion vdW interaction with positive atoms Lewis Acid
Charge Color Legend:
vdW interaction with positive atoms
Lewis Acid
General model