1. Carlos Cabezas and Yasuki Endo
Spectroscopic Characterization of the Reaction Products between HCl and the Simplest Criegee Intermediate CH2OO
Carlos Cabezas and Yasuki Endo
Department of Applied Chemistry
National Chiao Tung University
Taiwan

2. Bimolecular reactions with
Criegee Intermediates
Ozonolysis process of alkenes was first proposed by Rudolf Criegee in 1949
+ O3
POZ
Bimolecular reactions with
H2O, NO2, SO2, (H2O)2
Stabilized Criegee
Intermediates (SCIs)
Unimolecular
Dissociation,
OH radical

3. Background and Motivation
First direct detection of CH2OO by Taatjes et al. J. Am. Chem. Soc. 130, (2008)
CH2OO by Rotational Spectroscopy
Nakajima & Endo, J. Chem. Phys. 139, (2013) → FTMW, structure
McCarthy et al., J. Phys. Chem. Lett. 4, 4133 (2013) → FTMW, structure
Daly et al. J. Mol. Spectrosc. 297, 16 (2014) → submmW (up to THz)
Nakajima et al. Chem. Phys. Lett. 621, 129 (2015) → CH2OO excited states
Womack et al., Sci. Adv. 1, e (2015) → FTMW, O3 + C2H4

4. Background and Motivation
Reaction systems: CH2OO + H2O
Nakajima & Endo J. Chem. Phys. 140, (2014) → CH2OO···H2O complex
Nakajima & Endo J. Chem. Phys. 143, (2015) → Reaction Product HMHP
In addition to H2O, NO2, SO2, there exist other trace gases present in the polluted urban atmospheres that can react with SCIs
HCl (biogenic and anthropogenic sources) presents mixing ratios similar to those of SO2 and has recently been proposed as a SCIs sink
CH2OO + HCl → ???

5. Double Resonance Setup
Experimental
FTMW spectrometer
Double Resonance Setup
Jet
Monitor MW
Probe
MW or mmW
Frequency region : 4 – 40 GHz
Repetition rate: 10 Hz
MW as well as mm-wave sources can be used for the pump radiation

6. Pulsed discharge nozzle Experimental conditions
CH2I2
O2 + HCl in Ar
Experimental conditions
Mixture of 2% O % HCl in Ar
CH2I2 in a sample holder
Discharge voltage 800 V
Backing pressure 1.5 atm

7. CH2OO + HCl reaction PES Previous calculations at CCSD(T)/cc-pVDZ*
Previous calculations at CCSD(T)/cc-pVDZ
by Foreman et al. Angew. Chem. Int. Ed. 2016, 55, 10419
*kcal/mol, CCSD(T)/aug-cc-pVTZ

8. Ab initio calculations
HCl-CH2OO-I
HCl-CH2OO-II
CMHP-I
CMHP-II
MCP-I
MCP-II
MCP-III
A / MHz a
11231
26552
14304
35514
16420
35700
13369
B / MHz
2783
1687
3583
2636
3570
2869
4162
C / MHz
2325
1587
3096
2511
3216
2702
3240
|µa|
3.0
8.1
0.4
2.1
1.2
1.6
0.7
|µb|
4.8
2.0
0.3
1.8
2.6
|µc|
0.9 -
1.5
0.5
χaa / MHz b
-25.6
-36.7
-26.1
-56.8
-53.5
-92.3
-39.1
χbb / MHz
11.1
-3.1
17.9
5.9
30.5
-21.3
χab / MHz
30.8
28.5
44.5
36.4
73.2
60.3
80.8
χac / MHz
5.1
15.0
χbc / MHz
3.7
15.4
22.8
ΔE/ kcalmol-1
38.5
39.9
4.5
40.8
44.3
50.2
a Geometry optimizations at the CCSD(T)/aug-cc-pVTZ level of theory (MOLPRO ); b MP2/aug-cc-pVTZ with CCSD(T)/aug-cc-pVTZ geometry (Gaussian 09)

9. rotational transition 110-000
Rotational Spectrum
Strong signal of the 101–000 pure rotational transition of CH2OO was observed at MHz during the experiment, confirming an efficient production of CH2OO
35Cl 110 – 000
37Cl 110 – 000
35Cl 101 – 000 monitoring
F=2.5–1.5 component of the
rotational transition
22 transitions (a-, b- and c-types)
140 hyperfine components
18 transitions (a-, b- and c-types)
98 hyperfine components

10. Molecular Constants 35Cl 37Cl A* 14371.61597(45) 14325.37049(48) B
(20)
(26) C
(17)
(19)
103ΔJ
3.1410(63)
3.0053(71)
103ΔJK
(53)
(77)
103ΔK
90.32(11) -
103δJ
0.8036(26)
0.7488(69)
χaa
(12)
(14)
χbb
(15)
(16)
χab
45.60(33)
35.58(36)
χac
16.0(12)
13.9(12)
χbc
15.98(27)
12.12(35) N
140 98
σ /kHz
2.2
2.0
HCl-CH2OO-I
HCl-CH2OO-II
CMHP-I
CMHP-II
MCP-I
MCP-II
MCP-III
11231
26552
14304
35514
16420
35700
13369
2783
1687
3583
2636
3570
2869
4162
2325
1587
3096
2511
3216
2702
3240
-25.6
-36.7
-26.1
-56.8
-53.5
-92.3
-39.1
2.0
11.1
-3.1
17.9
5.9
30.5
-21.3
30.8
28.5
44.5
36.4
73.2
60.3
80.8
5.1 -
15.0
0.7
3.7
15.4
0.3
22.8
* All in MHz

11. pre-reactive complexes
CH2OO + HCl Vs. CH2OO + H2O
Present Work CH2OO + HCl
Previous Work CH2OO + H2O*
Similar energies for
pre-reactive complexes
Different energies
for TS1
*Nakajima & Endo J. Chem. Phys. 140, (2014)
*Nakajima & Endo J. Chem. Phys. 143, (2015)

12. Summary and Future Work
Present study reports the study of the reaction between HCl and the simplest Criegee intermediate using rotational spectroscopy. The addition product, CMHP, has been detected
These results together with those for the CH2OO+H2O system confirm FTMW as a good method to probe reactions of these unstable systems
Reactions of CH2OO with other trace gases and with organic compounds such as H2CO or HCOOH
Reactions of larger Criegee intermediates with conformational isomerism to understand their reactivity’s conformational dependence

13. Thanks for your attention