Microwave spectroscopy of 2-furancarboxylic acid

Roman A. Motiyenko, Manuel Goubet, Laurent Margulès, Georges WlodarczakPhLAM Laboratory, University Lille 1, Villeneuve d’Ascq, France

Eugen A. Alekseev, Stanislav F. DyubkoInstitute of Radio Astronomy of NASU, Kharkov, Ukraine

Motivation

Ribose

furfural

furfuryl alcohol

2-furancarboxylic acid

JMS, vol. 240, pp. 93-101JMS, vol. 244, pp. 9-12 Series of studies of ribose decomposition products

63rd OSU SymposiumColumbus, 2008

TA11

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)

Ab initio

Cc Ct Tc Tt

E = 0.0 kJ/molµa = 1.7 Dµb = 2.0 D

E = 23.5 kJ/molµa = 4.2 Dµb = 3.2 D

E = 0.16 kJ/molµa = 1.8 Dµb = 0.7 D

E = 9.1 kJ/molµa = 4.6 Dµb = 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

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

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 pumpsampleheater

310 – 315 K

Ground states

Tc Ccexperiment ab initio experiment ab initio

A (MHz) 5239.815 5231.857 5238.513 5226.081B (MHz) 1638.518 1645.933 1633.138 1640.807C (MHz) 1248.758 1252.043 1245.552 1248.745ΔJ (kHz) 0.0671 0.0655 0.0657 0.0642ΔJK (kHz) 0.0671 0.0610 0.0597 0.0550ΔK (kHz) 0.6965 0.6941 0.7141 0.7066δJ (kHz) 0.0174 0.0172 0.0171 0.0170δK (kHz) 0.2085 0.1991 0.2046 0.1966

• excellent agreement between experimental and theoretical results: in most cases relative error is less than 1%

Tc : Jmax = 94, Kamax = 50 rms = 0.01 MHz wrms = 0.65

Cc : Jmax = 99, Kamax = 47 rms = 0.01 MHz wrms = 0.67

HJ (mHz) 0.005399(95) 0.00330(12) hJ (mHz) 0.002318(46) 0.001706(96) hJK (mHz) 0.0362(20) 0.0

by extending assignment for J up to 122 we can determine some sextic constants which are of order of µHz

rms 0.011 0.011 wrms 0.67 0.67

Excited vibrational states

Cc Tc

ring–COOH torsion 82.5 83.2

ring–COOH in-plane bending 180 182

ring–COOH out-of-plane bending 192 192

COOH bending 416 418

Low-frequency vibrations @MP2/aug-cc-pVTZ (cm-1)

Coriolis interactionsv = 0 vin=1 vout=1

A (MHz) 5239.815 5151.594 5327.050B (MHz) 1638.518 1640.470 1640.542C (MHz) 1248.758 1250.779 1248.426ΔJ (kHz) 0.0671 0.0654 0.0645ΔJK (kHz) 0.0671 0.3355 -0.1991ΔK (kHz) 0.6965 -20.31 20.85δJ (kHz) 0.0174 0.0179 0.0189δK (kHz) 0.2085 -1.661 1.870

• rotational parameters are contaminated by an interaction• corresponding treatment is needed

coroirot HEHH

zJaacor PPGGiH )( 2

for the states vin and vout a-type interaction has been considered

vin=1 vout=15242.501 5236.1531640.560 1640.6241250.688 1248.345

0.0683 0.06830.119 0.115

0.69fixed 0.69fixed

0.0177 0.01800.206 0.242ΔE=410849.35( 66) MHz

Ga=6095.45(17) MHzGa

J=-0.00428(17) MHz

∆E (cm-

1)

experim. theory

13.7 10

Summary of results

Tc Cc

Number of lines σ (MHz) J

maxKa

maxNumber of

lines σ (MHz) J max

Ka max

v=0 1366 0.011 122 50 3348 0.011 122 47vt=1 1115 0.011 94 43 2808 0.012 99 45vt=2 681 0.011 47 26 1117 0.014 51 21vt=3 637 0.013 47 26 995 0.014 50 19vt=4 463 0.016 47 23 - - - -vin=1 394 0.015 46 20 381 0.013 48 20vout=1 410 0.015 46 24 391 0.013 48 21vt=1,vin=1 404 0.015 47 20 - - - -

Acknowledgements

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