Infrared Absorption of CH3SONO Detected with Time-Resolved
Fourier-Transform Spectroscopy
Yuan-Pern Lee
Dept. Applied Chemistry & Inst. Molecular ScienceNational Chiao Tung University, Hsinchu, Taiwan
Outline Step-scan FTIR for Reaction Intermediates Introduction of step-scan FTIR Absorption mode transient species CH3SO, CH3SO2, CH3SOO, CH3OSO
Reactions of CH3S + NO2
Low pressure: CH3SO + NO & CH3SNO2
High Pressure: CH3SONO
Fixed mirror
Movable mirror F
M
Fourier Transform IR Spectrometer(step scan)
time t
mirror position
Data Processing of Step-scan FTIR
FFT
xn: optical pathtm: time evolution of the process I: intensity of the interferogram
mirror position
time t
Experimental Setup (Absorption)10 ns / 0.07 cm1
1 s / 0.3 cm1
AC/DC detection in absorption
Strategy II AC/DC detection Uhmann/Becker/Taran/Siebert Appl. Spectrosc. 45, 390 (1991)
At ( )=ln(1+St ( )/S0( ))
St ( )=St (r)( )cos+St
(i)( )sin
S0( )
DCchannel:I0(g)
( ) St (r )( ),St
(I )( )
It (g)
ACchannel:Ig(t) sorting
FT
FT
Uhmann et al. Appl. Spectrosc. 45, 390 (1991)
1920 1900 1880 1860 1840 1820 1800 1780
0
5
100
5
100
5
100
5
10
X Axis Title
Abs
orba
nce/
10-3
t,t-CH3C(O)OO
t,c-CH3C(O)OO
Infra
red
inte
nsity
/a.u
.
cis
trans
1900 1880 1860 1840 1820 1800
0
6
0
6
0
6
0
6
a:b=54:46
Wavenumber/cm-1
c-type
b-type
a-type
Infr
ared
inte
nsi
ty/a
.u.
1920 1900 1880 1860 1840 1820 1800
0
6
0
6
0
6
0
6
a:b=0:100
Wavenumber/cm-1
c-type
b-type
a-type
Infr
ared
inte
nsi
ty/a
.u.
CH3C(O)O2
c-CH3C(O)O2
t-CH3C(O)O2
Assignment: (3) Rotational ContourJ. Chem. Phys. 132, 114303 (2010).
Importance of CH3SOx Barone/Turnipseed/RavishankaraFaraday Discuss. 100, 39 (1995)
CH3 + SO2 to form CH3SO2 A1
SO2 antisymmetric stretch
obs. : 1280cal. : 1262
A2 SO2 symmetric stretch
obs. : 1076cal. : 1074
J. Chem. Phys. 124, 244301 (2006)
0
2
0
2
0
2
0
1
0
1
1500 1400 1300 1200 1100 10000
1
A2A1
SO2CH
3I
x0.03
Abs
orban
ce/10
-3 Afterirr.20-80s
Static
Corrected
CH3SO
2
syn-CH3OSO
IRint
ensit
y/10
2 kmm
ol-1
Wavenumber/cm-1
anti-CH3OSO
100011001200130014001500
0
10
20
30
F
B
D
E
C
30-36s
12-18s
6-12s
Absorbance/1
0-3
Wavenumber/cm-1
0-6s
s
A
SO2
SO2
Photolysis of CH3SSCH3 in O2
Photolysis at 248 nm of CH3SSCH3/O2 ( 1/700, total 220 Torr ) at 260 K
CH3S + O2 CH3SOO
J. Chem. Phys. 133, 184303 (2010).
CH3SO
1020104010601080110011200
3
6
0
1
2
3
0
1
2
3
0
1
2
(D)Experiment
Abs.
/10
-3
Wavenumber/cm-1
Inte
nsi
ty/
a.u.
(A)a-type
(C)a/b=0.7/0.3
(B)b-type
Reaction Mechanism of CH3S + O2
A (1110 cm1), B(1397 cm1): syn-CH3SOO
C (1071 cm1): CH3SOE (1170 cm1): CH3S(O)OSCH3
F (1120 cm1): CH3S(O)S(O)CH3
CH3SOO + CH3SOO 2 CH3SO + O2 DH = 286 kJ mol1
CH3SO + CH3SO CH3S(O)OSCH3 DH = 68 kJ mol1CH3SO + CH3SO CH3S(O)S(O)CH3 DH = 61 kJ mol1
C: CH3SO
A: CH3SOO
CH3SOO + CH3S 2 CH3SO
DH = 334 kJ mol1
Photolysis of CH3OSOCl in N2
J. Chem. Phys. 134, 094304 (2011)
IR absorption of CH3OSO
Comparison of Experiments with Calcn.CH3SO2 CH3OSO CH3SOO CH3SO
B3P86 Expt. B3P86 Expt. B3P86 Expt. B3P86 Expt.
1262 1280 3129 2988 1425 1397 1081 1071
1074 1076 3046 2955 1197 1110
1166 1154
JCP, 124, 244301 (2006).
1162 1151
1028 994 JCP, 133, 184303 (2010)
S=O stretch; O-O stretch; C-O stretch JCP 134, 094304 (2011)
Reaction of CH3S + NO2
Barone/Turnipseed/RavishankaraFaraday Discuss. 100, 39 (1995)
Products of CH3S + NO2
CH3S + NO2 → CH3SO + NO (1)
CH3S + NO2 + M → CH3SNO2 +M (2)
CH3S + NO2 → H2CS + HONO (3)
CH3S + NO2 + M → CH3SONO + M (4) ?
F(CH3SO) = 1.07 0.15 (PIMS, PT = 1 Torr)
F(NO) = 0.8 0.2 (LIF, PT = 300 Torr)
Domine, Murrells, Howard, J. Phys. Chem. 94, 5839 (1990).
Tyndall, Ravishankara, J. Phys. Chem. 93, 2426 (1989).
cis-CH3SONO(-132.9)(-122.5)(-154.2)
(-108.7)
(-93.6)
Wang et al., Chinese Chem. Lett. 13, 805 (2002). QCISD(T)/6-311++G(d,p)
S. K.
Tang et al., Int. J. Quantum Chem. 107, 1495 (2007).G3(MP2)
17
PES (singlet)
Experimental conditions
PT = 16 to 141 Torr (N2/DMDS/NO2 = 140/0.9/0.06)
R = 4 cm-1
Laser trigger = 4 Hz, 10 shots average on each step
CH3SSCH3 + 248 nm → 2 CH3S
(s DMDS) = 1.2410-18 cm2 molecule-1
F(CH3S) = 1.65 0.38(s NO2) = 2.7510-20 cm2 molecule-1
[NO2]/[CH3S] = 1.91015/3.11014 molecule cm-3
P(N2O4) < 0.1 mTorr18
A1
B
A2
C
SO2
19
NO2 DMDS
PT = 16.2 Torr
PT = 140.8 TorrA1 B
NO2DMDS
20
(a) 141 Torr (31-60 ms)
(b) 16.1 Torr (6-10 ms)
CH3SNO2
cis-CH3SONO
CH3SO
CH3SNO
(g) (g)
(g)
(g)
solid: calculationdash: experiment
A1 B
CA2
trans-HONOnO-H = 3591 cm-1
nN=O = 1700 cm-1
dNOH = 1263 cm-1
cis-HONODE = 1.7 kJ mole-1
nO-H = 3426 cm-1
nN=O = 1641 cm-1
21
(a) CH3SNO2
(b) cis-CH3SONO
(c) Expt. vs. simulationA1
A2
n4 = 1562 cm-1
n8 = 1260 cm-1
n4 = 1562 cm-1
PT = 16.2 Torr, 10-20 ms
22
(a) Experiments 50-70 ms
90-110 ms subtraction
(b) cis-CH3SONO
(c) Expt. vs. cis-CH3SONO
n4 = 1562 cm-1
PT = 140.8 Torr
A1
23
• Predicted IR intensity: CH3SO/CH3SONO/CH3SNO2=42/294/331• Integrated intensity:
CH3SO/CH3SONO/CH3SNO2=0.52/0.50/0.33• Relative branching ratio:
CH3SO/CH3SONO/CH3SNO2=1.00/0.14/0.08
Relative branching ratio
Pt (Torr) CH3SO + NO CH3SONO CH3SNO2 Reference
300 0.8 0.2 - - J. Phys. Chem. 93, 2426 (1989)
140.8 - 1 - This work
16.2 0.82 0.11 0.07 This work
4.2 0.87 0.08 0.05 This work
1 1.07 0.15 - - J. Phys. Chem. 94, 5839 (1990)
Reaction Kinetics (PT = 140.8 Torr)
25
k/10-11 cm3 molecule-1 s-1
Temp./K
Reference
10.1 ± 1.5 297 a6.28 ± 0.28 298 b10.8 ± 1.0 295 c5.1 ± 0.9 297 d
6.10 ± 0.90 298 e5.3 ± 1.6 298 This work
aChang, Wang, Wang, Hwang, Lee, J. Phys. Chem. A 104, 5525 (2000).bA. A. Turnipseed, S. B. Barone, A. R. Ravishankara, J. Phys. Chem. 97, 5926 (1993).cR. J. Balla, H. H. Nelson, J. R. McDonald, Chem. Phys. 109, 101 (1986).dF. Domine, T. P. Murrells, C. J. Howard, J. Phys. Chem. 94, 5839 (1990).eG. S. Tyndall, A. R. Ravishankara, J. Phys. Chem. 93, 2426 (1989).
1578-1564 cm-1 (A1)
Summary
• New products CH3SO, cis-CH3SONO and CH3SNO2 are identified in the reaction of CH3S + NO2.
– CH3SO:1071 cm-1
– cis-CH3SONO: 1562 cm-1
– CH3SNO2: 1560, 1260 cm-1
• The major products at high pressure (140.8 Torr) is cis-CH3SONO, whereas those at low pressure (4-16 Torr) is CH3SO; CH3SNO2 is the minor product.
• A simple kinetics model was employed to yield a second-order rate coefficient for reaction CH3S + NO2 as k = (5.3 1.6) 10-11 cm3 molecule-1 s-1, consistent with previous results.
26
ACKNOWLEDGMENTS
Li-Kang Chu
Jin-Dah Chen
Vibrational wavenumbers
CH3SNO2
a-n 2NO =1562 cm-1
s-n 2NO =1257 cm-1
gas phase
CH3SOnS-O=1071 cm-1
L.-K. Chu and Y.-P. Lee, J. Chem. Phys. 133, 1 (2010).H. Niki, P. D. Maker, C. M. Savage, and L. P. Breltenbach, J. Phys. Chem. 87, 7 (1983).
trans-HONOnO-H=3591 cm-1
nN=O=1700 cm-1
dNOH=1263 cm-1
cis-HONODE=1.7 kJ mole-1
nO-H=3426 cm-1
nN=O=1641 cm-1
J. -M. Guilmot, M. Godefroid, and M. Herman, J. Mol. Sprctro. 160, 387 (1993).J. -M. Guilmot, F. Mélen, and M. Herman, J. Mol. Sprctro. 160, 401 (1993).
28
Vibrational wavenumberscis-CH3SONO
nN=O=1633 cm-1 (294)
B3LYP/aug-cc-pVTZ
perp,trans-CH3SONO
perp,cis-CH3SONO
nN=O=1819 cm-1 (417)
nN=O=1815 cm-1 (305)
E=0
E=1.8 kJ mol-1
E=5.7 kJ mol-1
29
cis-CH3SONO CH3SO
A’/A”=0.9924B’/B”=0.9990C’/C”=0.9978
A’/A”=0.9950B’/B”=1.0035C’/C”=1.0022 30
CH3SNO2n4 n8
A’/A”=0.9972B’/B”=0.9997C’/C”=0.9992
A’/A”=0.9977B’/B”=0.9995C’/C”=0.9984 31