1. The Millimeter-Wave Spectroscopy of Hydantoin, A Potential Precursor of Glycine
Hiroyuki Ozeki, Rio Miyahara,
Hiroto Ihara, Satoshi Todaka,
Kaori Kobayashi, and Masatoshi Ohishi
(Toho Univ., Toyama Univ., NAOJ)
2016 Jun 21st
International Symposium on Molecular Spectroscopy, Illinois

2. Interstellar pre-biotic molecules
Amino acids
Glycine × Alanine ×
Sugars
Glycoaldehyde　○(2004)
Nucleic Acids (Building Block)
Pyrimidine, Imidazole, Pyrrole,,, ×

3. Road to Glycine Glycine Gas Phase Rxn. Dust Surface Rxn. Strecker Rxn.
CH3NH2
Gas Phase Rxn.
Dust Surface Rxn.
Strecker Rxn.
Gas-Dust Rxn.
Others

4. Hydantoin (Imidazolidine-2,4-dione)
White powder (m.p. 220 ℃)
Synthesized from glycolic acid and Urea
Synthesized from Carbonyｌ compounds via Bucherer-Bergs Reaction
Provides glycine by hydrolysis
5-substituted derivatives will lead to various kinds of amino acids
C3H4N2O2
5-substiuted Hydantoin

5. Hydantoin in meteorites
A. Shimoyama & R. Ogasawara (2002)

6. Hydantoin as a precursor of di- or oligo-peptides in primitive oceans
N-Carboxyanhydride amino acid
Carbamoyl acids
Peptides
Amino acids
P. Marcellus et al. (2011), A. Commeyras et al. (2004), G. Danger et al. (2006)

7. Aim of the study
To provide spectroscopic data for astronomical search

8. Previous spectroscopic studies on Hydantoin
X-ray crystallography
Y. Fang-Lei et al. (2005)
IR spectroscopy (solid) and ab initio
O. Gluce et al. (2012)
Matrix isoleation IR spectroscopy and ab initio
G. O. Ildiz et al. (2013)
Theoretical calculation
S. Belaidi et al. (2015)
No gas phase data

9. Molecular structure & Dipole moment of Hydantoin
～　6500 MHz B
～ MHz C
～ MHz b
mb ～3.3 D

10. Millimeter-wave spectroscopy of Hydantoin
Conventional frequency modulated spectrometer with 100 cm length free space Toho university
Experimental Condition
Sample : Commercially available sample (20 g)
Heated to 420 K
 Hydantoin does not decompose at this temperature
Spectral measurement
Frequency region : 80 – 150 GHz
Search for b-type transitions

11. Predicted b-type spectrum
Series with 3400 MHz ～140 GHz

12. Predicted b-type spectrum
N = 38 – 37
Ka = 2 – 3, 3 - 2
N = 39 – 38
Ka = 1 – 2, 2 - 1
N = 37 – 36
Ka = 3 – 4, 4 - 3
N = 40 – 39
Ka = 0 – 1, 1 - 0

13. Spectral line survey @ 142 GHz
800 MHz span

14. Spectral line survey @ 142 GHz
Ka = 3 – 4, 4 - 3
N = 38 – 37
Ka = 2 – 3, 3 - 2
N = 39 – 38
Ka = 1 – 2, 2 - 1
N = 40 – 39
Ka = 0 – 1, 1 - 0

15. Spectral assignments
+0 MHz
+3400 MHz
+6800 MHz
MHz

16. Spectral assignments
b-type R-branch transition

17. Molecular constants so far determined
Watson’s A-reduced Hamiltonian
Ground state
Excited state 1
Excited state 2
A (MHz)
(194)
(266)
(44)
B (MHz)
(99)
(32)
(53)
C (MHz)
(212)
(91)
(111)
D J (kHz)
(36)
0.0921(121)
0.2218(297)
D JK (kHz)
(275)
-0.71(65)
(82)
D K(kHz)
2.2666(78)
9.3(44)
(88)
dJ(kHz)
(181)
0.0234(61)
0.0882(149)
dK(kHz)
0.2853(36)
-0.18(32)
7.38(53)
# of obs. lines
129 66 79
rms 36 kHz

18. Spectral Intensity @ 420 K N = 35 - 34, Ka = 0-1,1-0 (121 GHz)
Intensity: Ground state > Excited state 1 > Excited state 2

19. Estimated vibrational energy
Present Study
Relative Intensity
Estimated energy (cm-1)
Excited state 1
0.61
145
Excited state 2
0.55
175
Comparison with calculations
Mode #
IR (Exp.)
DFT(B3LYP)
6-311G++(d,p)
Ildiz et al.(2012)
Belaidi et al (2015)
Ildiz et al.(2013) 27 29 26
133 25
356 24
428
385
Excited state 1  Mode Excited state 2  Mode 26

20. 100 K
Ground state

21. Conclusions
Pure rotational spectra of Hydantoin in the ground and 2 vibrationally excited states have been successfully assigned.
Frequency catalogues are now ready for astronomical observation of Hydantoin below 300 GHz.

22. Acknowledgements
This work has been supported by JSPS Kakenhi (Grants-in-Aid for Scientific Research) #15H03646