Microwave Spectroscopic Investigations of the C—H… p Containing Complexes CH 2 F 2 …Propyne and CH 2 ClF…Propyne Rebecca A. Peebles, Sean A. Peebles, Cori L. Christenholz, Yasser J. Dhahir, Anthony A. Ernst Department of Chemistry, Eastern Illinois University, Charleston, IL 61920
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Microwave Spectroscopic Investigations of the C—H… Containing Complexes CH 2 F 2 …Propyne and CH 2 ClF…Propyne Rebecca A. Peebles, Sean A. Peebles, Cori.
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Microwave Spectroscopic Investigations of the C—H…p Containing Complexes CH2F2…
Propyne and CH2ClF…Propyne
Rebecca A. Peebles, Sean A. Peebles, Cori L. Christenholz, Yasser J. Dhahir,
Anthony A. ErnstDepartment of Chemistry, Eastern Illinois University,
Charleston, IL 61920
C—H…p Interactions
Cl
F
80.0(16)°
3.122(46) Å148.7(7)°
2.724(7) Å
Sexton, et al., Phys. Chem. Chem. Phys.,12 (2010), 14263.
3.207(22) Å
101.0(1)°
3.236(6) Å
Elmuti, et al., Phys. Chem. Chem. Phys., 13 (2011), 14043.
3.293(40) Å
2.670(8) Å
153.2(5)°
81.6(14)°
Obenchain, et al., J. Phys. Chem. A, 115 (2011), 12228.
2.84(6) Å
94.9(3)°
3.363(14) Å
Obenchain, et al., in preparation.
Propyne Complexes
• New considerations– Two inequivalent C—H bond donors in propyne– Internal rotation
Possible Structures
I II III IV V
A / MHz 4650.1 5870.8 5783.0 4516.8 6482.7
B / MHz 1572.5 1422.6 1362.3 1568.9 1063.4
C / MHz 1513.1 1162.0 1118.3 1495.1 924.3
ma / D 0.01 1.53 1.66 0.01 2.58
mb / D 1.24 0.75 0.71 1.23 1.32
mc / D 0.00 0.00 0.00 0.00 0.00
Pcc / u Å2 48.0 3.2 3.2 48.0 3.2
Relative Energy / cm-1
0 27 35 58 234
Gaussian 03: MP2/6-311++G(2d,2p)
Experimental
• CH2F2…Propyne– Scanned on 480 MHz CP-FTMW– Sample: ~1.8% each CH2F2 and propyne in He/Ne
pressurized to 5.2 bar in 1 L tank – delivered to nozzle at ~2 bar
– 2000 gas and microwave pulses per frequency step– Isotopes on cavity FTMW• Enriched: CH3CCD (98% D, CDN Isotopes)• All four carbons in natural abundance
J = 3 - 2 J = 4 - 3
J = 5 - 4J = 6 - 5
AABS: Z. Kisiel, L. Pszczolkowski, I. R. Medvedev, M. Winnewisser, F.C .De Lucia, C . E. Herbst, J.Mol.Spectrosc., 233, (2005), 231.PROSPE Web SITE: Z.Kisiel, in: J. Demaison, et al. (Eds.), Spectroscopy from Space, Kluwer Academic Publishers, Dordrecht, 2001, pp.91-106.