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

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

Background and Motivation First direct detection of CH2OO by Taatjes et al. J. Am. Chem. Soc. 130, 11883 (2008) CH2OO by Rotational Spectroscopy Nakajima & Endo, J. Chem. Phys. 139, 101103 (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, e1400105 (2015) → FTMW, O3 + C2H4

Background and Motivation Reaction systems: CH2OO + H2O Nakajima & Endo J. Chem. Phys. 140, 134302 (2014) → CH2OO···H2O complex Nakajima & Endo J. Chem. Phys. 143, 164307 (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 → ???

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

Pulsed discharge nozzle Experimental conditions CH2I2 O2 + HCl in Ar Experimental conditions Mixture of 2% O2 + 0.2 % HCl in Ar CH2I2 in a sample holder Discharge voltage 800 V Backing pressure 1.5 atm

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

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 2012.1); b MP2/aug-cc-pVTZ with CCSD(T)/aug-cc-pVTZ geometry (Gaussian 09)

rotational transition 110-000 Rotational Spectrum Strong signal of the 101–000 pure rotational transition of CH2OO was observed at 23186.49 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 110-000 22 transitions (a-, b- and c-types) 140 hyperfine components 18 transitions (a-, b- and c-types) 98 hyperfine components

Molecular Constants 35Cl 37Cl A* 14371.61597(45) 14325.37049(48) B 3588.63374(20) 3499.32509(26) C 3099.07344(17) 3030.31755(19) 103ΔJ 3.1410(63) 3.0053(71) 103ΔJK -18.914(53) -18.294(77) 103ΔK 90.32(11) - 103δJ 0.8036(26) 0.7488(69) χaa -26.3708(12) -21.2241(14) χbb -3.9105(15) -2.6931(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

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, 134302 (2014) *Nakajima & Endo J. Chem. Phys. 143, 164307 (2015)

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

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