1. Microwave spectroscopy of 2-furancarboxylic acid Roman A. Motiyenko, Manuel Goubet, Laurent Margulès, Georges Wlodarczak PhLAM Laboratory, University Lille 1, Villeneuve d’Ascq, France Eugen A. Alekseev, Stanislav F. Dyubko Institute of Radio Astronomy of NASU, Kharkov, Ukraine

2. Motivation Ribose furfural furfuryl alcohol 2-furancarboxylic acid JMS, vol. 240, pp. 93-101 JMS, vol. 244, pp. 9-12 Series of studies of ribose decomposition products 63 rd OSU Symposium Columbus, 2008 TA11

3. 2-furancarboxylic acid No previous high resolution studies ▫ I.G John and L. Random, JACS 100, 3981-3991 (1978) : STO 3G structure and conformational analysis ▫ M.V. Roux et al., J. Phys. Chem. A 107, 11460-11467 (2003) : thermochemical properties and MP2(full)/6-31G(3df,2p) structure of only one conformation supposed to be the most stable. Conformations: Cis-cis (Cc) Cis-trans (Ct) Trans-cis (Tc) Trans-trans (Tt)

4. Ab initio E = 0.0 kJ/mol µ a = 1.7 D µ b = 2.0 D E = 23.5 kJ/mol µ a = 4.2 D µ b = 3.2 D E = 0.16 kJ/mol µ a = 1.8 D µ b = 0.7 D E = 9.1 kJ/mol µ a = 4.6 D µ b = 1.6 D structure and molecular force field were optimized at MP2 level of theory and using aug-cc-pVTZ basis set 4 geometries have been considered calculations are not able to point out which conformer of 2-furancarboxylic acid Cc or Tc is the most stable but only that they are very close in energy

5. FTMW spectroscopy Carrier gas P= 1.5 bars (Ne) Inside the cavity… (not at the scale) Heated nozzle T= 330 – 340 K Mirror sample measurements in 5 – 20 GHz frequency range sample heated up to 340 K both Cc and Tc conformations have been observed and assigned

6. Absorption spectroscopy Microwave spectrometer in Kharkov: 50 – 120 GHz Microwave spectrometer in Lille: 150 – 305 GHz, 580 – 600 GHz Both Cc and Tc conformations as well as their lowest excited vibrational states have been assigned An attempt to assign Tt conformer which have relatively high dipole moment was unsuccessful Source of radiation Absorbing cell Detector to diffusion + rotary pump sample heater 310 – 315 K

7. Ground states excellent agreement between experimental and theoretical results: in most cases relative error is less than 1% by extending assignment for J up to 122 we can determine some sextic constants which are of order of µHz

8. Excited vibrational states CcTc ring–COOH torsion 82.583.2 ring–COOH in- plane bending 180182 ring–COOH out- of-plane bending 192 COOH bending416418 Low-frequency vibrations @MP2/aug-cc-pVTZ (cm -1 )

9. Coriolis interactions rotational parameters are contaminated by an interaction corresponding treatment is needed for the states v in and v out a-type interaction has been considered ∆E (cm -1 ) experim.theory 13.710

10. Summary of results Tc Cc Number of lines σ (MHz) J max K a max Number of lines σ (MHz) J max K a max v=0 13660.0111225033480.01112247 v t =1 11150.011944328080.0129945 v t =2 6810.011472611170.0145121 v t =3 6370.01347269950.0145019 v t =4 4630.0164723---- v in =1 3940.01546203810.0134820 v out =1 4100.01546243910.0134821 v t =1,v in =1 4040.0154720----

11. Acknowledgements INTAS foundation (YSF ref. n0. 06-1000014-5984) GdR SpecMo