Fixed mirror Movable mirror F M time t mirror position.

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