1. Microwave and infrared spectra of urethane
Roman A. Motiyenko, Manuel Goubet, Justin Habinshuti, Therese H. Huet
Laboratoire PhLAM, Universite Lille 1, Villeneuve d’Ascq Cedex, France
Eugen A. Alekseev
Institute of Radio Astronomy of NASU, 4, Chervonopraporna str., Kharkov, Ukraine
Pierre Asselin, Pascale Soulard
Universite Pierre et Marie Curie, Bat. F74 - Case 49, 4 place Jussieu, F , Paris Cedex 05, France

2. Urethane (ethyl carbamate)
Two lowest-energy conformers: I and II
Important astrophysical precursors: NH3 and C2H5OH
Possible carcinogen and is present in some alcoholic beverages, therefore should be controlled
Conformer I
Previous study:
K. M. Marstokk and H. Mollendal, Acta Chem. Scandinavica, vol. 53, (1999)
Microwave spectra of the conformers I and II of urethane in 16.5 – 56 GHz frequency range
14N hyperfine structure was not resolved → relatively large errors for this frequency range ~0.1 MHz
MP2/cc-pVTZ and B3LYP/6-31G* ab initio calculations
Conformer II

3. MWFT spectroscopy
Microwave Fourier transform spectrometer with a pulsed supersonic jet. Spectra were obtained in the frequency range 5 – 20 GHz. The spectral resolution about 10 kHz allowed to study nuclear quadrupole and spin-spin hyperfine structures
Carrier gas
P= 1.5 bars (Ne)
Inside the cavity…
(not at the scale)
Heated nozzle
T= 373±2 K
Mirror
Urethane

4. Conformer I reassignment
Basis for predictions: K. M. Marstokk and H. Mollendal, Acta Chem. Scandinavica, vol. 53, (1999) (*)
Q-type transitions were easily assigned
Problems with R-type transitions. Lines are not in their positions ± 10 MHz!!!
According to (*):
A= MHz
B= MHz
C= MHz
111 ← 000 : A+C = MHz
10755 MHz
212 ← 101 : A+3C = MHz
14288 MHz
Reason:
Wrong assignment of weak aR-type in (*)
a ~ 0.6 D
A=8989 MHz
B=2136 MHz
C=1766 MHz
!!!

5. Hyperfine structure

6. MW conventional spectroscopy
MW spectrometer in Kharkov
Frequency range in this study: 50 – 150 GHz
Resolution: 50 – 100 kHz – hyperfine structure is partially resolved
Precision in this study: 10 kHz
MW spectrometer in Lille
Frequency range in this study:150 – 250 GHz
Resolution: 100 – 300 kHz – hyperfine structure is not resolved
Precision in this study: 20 – 40 kHz
No heated absorbing cell available → the sample was heated only up to 313 K.

7. MW spectrometer in Kharkov
BWO, 50 – 150 GHz
PLL
IF = 25 MHz
FM modulated synthesizer
25 MHz
Klystron 3.4 – 5.2 GHz
IF = 5 MHz
Absorbing cell
Amplifier
Lock-in detector
Sine wave synthesizer
7 – 120 KHz
DAC
DDS AD9851
30 – 60 MHz
Band-pass amplifier MHz
Synthesizer 360 MHz
Frequency divider f/2
Frequency Doubler (optional)
Detector Schottky
Reference synthesizer MHz

8. MW spectrometer in Lille
BWO power source
BWO
Bolometer
Absorbing cell
PLL
IF = 312 – 328 MHz
Amplifier
Fmod=5 kHz
Synthesizer
НР 3326В
MHz
Synthesizer
НР 83711В
2 – 20 GHz
Lock-in detector
GPIB bus
PLL lock control
GPIB controller
ADC
ADuC 834

9. Microwave spectra (Kharkov)
The strongest lines correspond to Ka = 11← 10 series of bQ1,-1 transitions of conf. II

10. Microwave spectra (Lille)
The series of Ka = 20← 19 series of bQ1,-1 transitions of conf. II is well observable

11. MW results for conformer I
Rotational parameters (A-reduction)
Hyperfine structure parameters
Ground state
va=1
va=2
A, MHz
(13)
(13)
(78)
B, MHz
(25)
(14)
(65)
C, MHz
(25)
(19)
(17)
ΔJ, kHz
(13)
0.1882(18)
0.2215(77)
ΔJK, kHz
(98)
1.246(94)
1.25(18)
ΔK, kHz
5.2602(15)
6.18(10)
7.05(39)
δJ, kHz
(32)
(10)
(37)
δK, kHz
(18)
0.499(65)
1.534(33)
HJ, Hz
(26)
HJK, Hz
(12)
HKJ , Hz
(47)
HK, Hz
0.0387(50)
hJ, Hz
(10)
hJK, Hz
(95)
hK, Hz
0.0208(28)
Nlines
962
138
120
RMS, MHz
0.0128
0.0069
0.0070
Quadrupolar GS
va=1
va=2
χaa, MHz
2.1171(13)
1.25(85)
1.47(53)
χbb, MHz
2.1665(29)
2.5(13)
2.54(87)
χcc, MHz
(16)
-3.82(47)
-4.01(34)
Spin-spin GS
3/2Daa, kHz
-40.3(24)
3/2Dbb, kHz
14.0(63)
3/2Dcc, kHz
26.3(39)

12. MW results for conformer II
Rotational parameters (A-reduction)
Hyperfine structure parameters
Ground state
vt=1
va=1
A, MHz
(90)
(11)
(17)
B, MHz
(28)
(49)
(54)
C, MHz
(34)
(31)
(68)
ΔJ, kHz
(20)
(49)
(50)
ΔJK, kHz
(10)
1.4546(16)
(33)
ΔK, kHz
(59)
11.009(13)
14.496(22)
δJ, kHz
(62)
(20)
(88)
δK, kHz
(65)
(21)
-2.385(11)
HJ, Hz
(44)
HJK, Hz
(13)
(17)
(11)
HKJ , Hz
(39)
-0.122(17)
(29)
HK, Hz
(98)
hJ, Hz
(15)
hJK, Hz
(47)
hK, Hz
0.6947(28)
Nlines
1121
240
145
RMS, MHz
0.0124
0.0153
0.0101
Quadrupolar GS
vt=1
va=1
χaa, MHz
1.8921(11)
2.17(59)
1.38(54)
χbb, MHz
1.8922(22)
1.72(88)
2.16(83)
χcc, MHz
(11)
-3.89(29)
-3.54(29)
Spin-spin GS
3/2Daa, kHz
-61.4(15)
3/2Dbb, kHz
34.7(31)
3/2Dcc, kHz
26.7(16)

13. Ab initio structure Conformer I Conformer II
A (MHz)
B (MHz)
C (MHz)
a (Deb.)
b (Deb.)
c (Deb.)
MP2/
G(3df,2p)
9007.9
2151.9
1776.2
0.63
2.51
0.61
7588.5
2443.5
2133.1
0.07
2.28
1.06
aug-cc-pVDZ
8835.4
2118.2
1747.7
-0.66
-2.48
0.69
7423.1
2411.8
2102.4
-0.01
-2.23
1.16
aug-cc-pVTZ
8984.4
2148.1
1773.0
0.65
2.48
0.67
7571.7
2439.6
2127.9
0.01
2.25
1.11
cc-pVQZ
9028.5
2158.0
1781.3
0.60
0.68
7612.0
2448.3
2136.6
0.05
1.12
Experiment
8989.5
1766.5
7565.4
2414.8
2116.4
In case of long range interactions addition of diffuse functions makes calculations more precise

14. Conformational stability
According to H. Mollendal Conformer I is found to be 0.12(12) kcal/mol more stable than Il by relative intensity measurements.
MP2/
G (3df,2p)
aug-cc-pVDZ
aug-cc-pVTZ
cc-pVQZ
E(MP2)
E(MP2) – ZPE
Conf. I, kcal/mol
Conf. II, kcal/mol
I–II, kcal/mol
0.10
0.21
0.01
0.08

15. IR spectra assignment (preliminary)
Spectral range: 1000 – 1900 cm-1
Resolution: 0.1 cm-1
Conformer I
Conformer II 
MP2/aug-cc-pVTZ
Exper.
I (km/mol)
n (cm-1)
15
140.7
1126.7
1078
19
425.1
1353.0
1333
20
62.0
1412.4
1379
25
119.4
1623.2
1580
26
410.2
1806.9
1778 
MP2/aug-cc-pVTZ
Exper.
I (km/mol)
n (cm-1)
16
111.3
1136.1
1107
18
20.0
1342.3
1267
19
353.8
1358.3
1330
20
54.2
1408.7
1375
21
25.5
1431.9
1401
25
121.0
1621.8
1580
26
392.1
1805.3
1769

16. Acknowledgements PEPCO-NEI network (project nr 509031H)
INTAS (YSF grant, ref. nr )
PhLAM laboratory and G. Wlodarczak

17. Thank you for your attention!