Files in this item

FilesDescriptionFormat

application/vnd.openxmlformats-officedocument.presentationml.presentation

application/vnd.openxmlformats-officedocument.presentationml.presentation1331843.pptx (15MB)
PresentationMicrosoft PowerPoint 2007

application/pdf

application/pdf3629.pdf (22kB)
AbstractPDF

Description

Title:THE REACTION OF CH2OO WITH HNO3 INVESTIGATED WITH A STEP-SCAN FTIR SPECTROMETER
Author(s):Chung, Chen-An
Contributor(s):Lee, Yuan-Pern ; Hsu, Cho-Wei
Subject(s):Atmospheric science
Abstract:Carbonyl oxides, which are known as Criegee intermediates, are important intermediates produced in ozonolysis of unsaturated hydrocarbons.\footnote{R. Criegee, Angew. Chem. Int. Edit. 14, 745 (1975).} Criegee intermediates react readily with other atmospheric species such as \chem{HNO_3}, \chem{SO_2}, (\chem{H_2O})$_{2}$ and HCOOH, leading to production of OH, aerosols and organic acids in the atmosphere. The reaction coefficient between \chem{CH_2OO} and \chem{HNO_3} was reported to be 5.4$\times$10$^{-10}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$ at 298 K. \footnote{E. S. Foreman, K. M. Kapnas and C. Murray, Angew. Chem. Int. Edit. 55, 10419 (2016).} Theoretical calculations also predict a similar rate coefficient for \chem{CH_2OO} + \chem{HNO_3}, the reaction goes through a barrierless path to form nitrooxymethyl hydroperoxide (NMHP, \chem{NO_3CH_2OOH}). Besides, due to large exothermicity(-184.9 kJ mol$^{-1}$), internally excited NMHP might decompose further to \chem{CH_2ONO_3} and OH.\footnote{P. Raghunath, Y. P. Lee and M. C. Lin, J. Phys. Chem. A 121, 3871 (2017).} In this work, we utilized a step-scan FTIR coupled with a multipass White cell to record time-resolved IR absorption spectra of the reactants and products during the reaction of \chem{CH_2OO} with \chem{HNO_3} in a flow system with total pressure about 10 Torr. \chem{CH_2OO} was produced from the reaction of \chem{CH_2I} + \chem{O_2}; \chem{CH_2I} was produced from photolysis of \chem{CH_2I_2} at 308 nm.\footnote{O. Welz, J. D. Savee, D. L. Osborn, S. S. Vasu,C. J. Percival, D. E. Shallcross and C. A. Taatjes, Science 335, 204 (2012).} The IR absorption spectra were recorded at instrumental resolution 0.3 \wn. Newly observed bands at 825, 967, 1053, 1294, 1348, 1424, 1686 and 3587 \wn can be assigned to NMHP. The observed wavenumbers and relative intensities agree with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3LYP/aug-cc-pVTZ method. In addition, we also observed several bands with clear rotational structure, which can be assigned to the absorption of \chem{NO_2}, \chem{H_2CO} and \chem{HO_2}. Observation of these species indicates that another decomposition route for excited NMHP might exist. Furthermore, absorption bands of unternally excited \chem{HNO_3} was also observed at low pressure, indicating that decomposition of pre-reaction complex can excite \chem{HNO_3}. By probing the formation of NMHP and \chem{NO_2}, the rate coefficient of this reaction was determined to be (5.3$\pm$0.8)$\times$10$^{-10}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$.
Issue Date:2019-06-20
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Type:Text
Language:English
URI:http://hdl.handle.net/2142/104308
DOI:10.15278/isms.2019.RJ07
Rights Information:Copyright 2019 Chen-An Chung
Date Available in IDEALS:2019-07-15
2020-01-25


This item appears in the following Collection(s)

Item Statistics