Laboratory Detections of Cyanothioformaldehyde (HCSCN) and
Mercaptoacetonitrile (HSCH2CN) by CP-FTMW Spectroscopy
DANIEL P. ZALESKI, JUSTIN L. NEILL, MATT T. MUCKLE,
NATHAN A. SEIFERT, AMANDA L. STEBER, BRENT J.
HARRIS, and BROOKS H. PATE
Department of Chemistry, University of Virginia, McCormick Rd,
Charlottesville, VA. 22904,USA.
VALERIO LATTANZI and MICHAEL C. MCCARTHY
Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138, and School of Engineering & Applied
Sciences, Harvard University, 29 Oxford St., Cambridge MA
02138.
ANTHONY J. REMIJAN
National Radio Astronomy Observatory, 520 Edgemont Rd.,
Charlottesville, VA 22904-2475.
The Ohio State 67th International Symposium on Molecular Spectroscopy, June 21st, 2012.
Reaction Product Screening by Broadband Rotational Spectroscopy
CH3CN + H2S
(0.4%, 0.4% in neon, 1.1 kV)
x4000
388,000 spectrum averages
(40,000:1)
100 MHz
Jens-Uwe Grabow, E. Samuel
Palmer, Michael C. McCarthy, and
Patrick Thaddeus, Rev. Sci. Instrum.
76, 093106, (2005).
C. Karunatilaka, A. J. Shirar, G. L.
Storck, K. M. Hotopp, E. R. Biddle,
R. Crawley, and B. C. Dian. Phys.
Chem. Lett. 1, 1547-1551, (2010).
Laboratory Reaction Chemistry
Molecule
SH
SSH
NCS
SO2
OCS
HSCN
HNCS
HCNS
H2CS
CCCS
HCCCN
HCCNC
CH2CN
H2CCS
HCSCN
CH3NC
CH3SH
H2CCNH
CH2CHCN
CH2CHNC
HSCH2CN
CH3CCH
CH3CCCN
H2CCCHCN
CH3CH2CN
Number
Atoms
2
3
3
3
3
4
4
4
4
4
5
5
5
5
5
6
6
6
7
7
7
7
8
8
9
Interstellar
Y
N
N
Y
Y
Y
Y
N
Y
Y
Y
Y
Y
N
N
Y
Y
Y
Y
N
N
Y
Y
Y
Y
Radical-Radical Chemistry in the Discharge Source
∙CH3 + ∙CH2CN  CH3CH2CN
-421 kJ/mol
CH3CH2CN
 CH2CHCN + H2
+163 kJ/mol
CH2CHCN
 HCCCN + H2
+207 kJ/mol
----------------------------------------------------------------------CH3CH2CN
 HCCCN + 2H2
+370 kJ/mol
Also: Isomerization to form isonitriles and H-shifts
Summary of CH3CN + H2S Discharge Chemistry
26 molecular species identified (including radicals)
20 known interstellar species (>10% of all known)
3 new interstellar detections (HSCN, E- and Z-ethanimine)
Two new molecules identified (HSCH2CN, HCSCN)
More than 50% of transitions at 3:1 are unassigned
Experiment
24 Gs/s
AWG
x3
No Helmholtz coil
Gordon G. Brown, Brian C. Dian, Kevin O. Douglass, Scott M.
Geyer, Steven T. Shipman, and Brooks H. Pate. Rev. Sci.
Instrum. 79, 053103, (2008).
Jens-Uwe Grabow, E. Samuel Palmer, Michael C. McCarthy,
and Patrick Thaddeus, Rev. Sci. Instrum. 76, 093106, (2005).
40 - 60 GHz CP-FTMW Spectrometer
100 mW
FC01 – 40-60 GHz
cavity
New Lab Detections Predicted From This
Chemistry
SH + CH2CN  HSCH2CN
HSCH2CN
 HCSCN + H2
-313 kJ/mol
+135 kJ/mol
MP2/6-31+G(d,p)
Previous Work on Cyanothioformaldehyde - HCSCN
10-2 mbar
700 °C – thermolysis temperature
130 – 280 GHz region
a- and b-type tranistions
M. Bogey et al. J. Am. Chem.
Soc., 111, (1989), 7399-7402.
HCSCN Spectral Parameters
EXP
Bogey et al
A (MHz)
42909.9686(83)
43314.0052(34)
B (MHz)
3195.3952(17)
3205.67686(24)
C (MHz)
2970.1273(18)
2975.32470(23)
ΔJ (kHz)
1.218(11)
1.26557(17)
ΔJK (kHz)
-105.78(38)
-102.0177(24)
δJ (kHz)
0.2173(93)
-0.228786(42)
1.5Xaa (MHz)
-5.295(34)
-
0.25(Xbb-Xcc) (MHz)
-0.455(15)
-
36 lines
22.1 kHz RMS
M. Bogey et al. J. Am. Chem.
Soc., 111, (1989), 7399-7402.
152 lines
28.8 kHz RMS
800,000 avg
~2.5 hr
707-606
EXP
MP2/6-311++G(d,p)
A (MHz)
42909.9686(83)
42457.6130
B (MHz)
3195.3952(17)
3151.01280
C (MHz)
2970.1273(18)
2933.32010
1.5Xaa (MHz)
-5.295(34)
-4.4140
0.25(Xbb-Xcc) (MHz)
-0.455(15)
-0.2320
mmW Simulation on CP-FTMW Spectrum
CP-FTMW determined
202-101
Isotopic Confirmation
34S
obtained in natural abundance
15N from discharging CH C15N
3
D from CD3CN
Comparison of Kraitchman Structures
CP-FTMW
mmW
ab initio (larger spheres): MP2/6-311++G(d,p)
experimental positions (smaller spheres)
J. Kraitchman. Amer. J. Phys., 21, (1953), 17-24.
Mercaptoacetonitrile – HSCH2CN
HSCH2CN Spectral Parameters
EXP
M062X/6-311++G(d,p)
A0 (MHz)
A1 (MHz)
23109.608(26)
23110.087(27)
23133.817
B0 (MHz)
B1 (MHz)
3105.249(28)
3105.189(28)
3105.6791
C0 (MHz)
C1 (MHz)
2820.357(28)
2820.584(28)
2825.7701
ΔJ0 (kHz)
2.650(58)
-
ΔJK0 (kHz)
58.53(61)
-
δJ0 (kHz)
491(45)
-
δK0 (kHz)
-196(13)
-
1.5Xaa0 (MHz)
-4.003(45)
-4.446
0.25(Xbb-Xcc)0 (MHz)
-0.230(44)
0.425
30 lines per state
26.7 kHz RMS
Torsional Motion
Calculated Energy Gap:
trans
cis
4.98 GHz using the 1D torsional
method of Pitzer
5.13 GHz using WKB
gauche
Blue – PES
Red – Probability Distribution
K. S. Pitzer, J. Chem. Phys., 14, 239, (1946)
Search for HCSCN and HSCH2CN in the
GBT PRIMOS Survey
Neither species was observed in the PRIMOS data
from 7.7 - 48.9 GHz towards Sagittarius B2(N)
Conclusions
Constructed a 40-60 GHz CP-FTMW spectrometer
Measured HCSCN up to 60 GHz
And HSCH2CN up to 42 GHz (able to measure 2 transitions
slightly out of band)
A Kraitchman substitution structure for HCSCN was obtained
Anharmonic calculations suggest the previous study assigned
a vibrationally excited state
Neither species was observed in the GBT PRIMOS survey
Acknowledgments
Centers for Chemical Innovation
Award Number 0847919
0960074