Avery B. Dalton, Lisa M. Wingen, Sergey A. Nizkorodov
{"title":"吲哚 + NO3 有机气溶胶中硝基吲哚发色团的异构体鉴定","authors":"Avery B. Dalton, Lisa M. Wingen, Sergey A. Nizkorodov","doi":"10.1021/acsphyschemau.4c00044","DOIUrl":null,"url":null,"abstract":"Oxidation of indole by nitrate radical (NO<sub>3</sub>) was previously proposed to form nitroindole, largely responsible for the brown color of indole secondary organic aerosol (SOA). As there are seven known nitroindole isomers, we used chromatographic separation to show that a single nitroindole isomer is produced in the indole + NO<sub>3</sub> reaction and definitively assigned it to 3-nitroindole by comparison with chromatograms of nitroindole standards. Mass spectra of aerosolized 3-nitroindole particles were recorded with an aerosol mass spectrometer and directly compared to mass spectra of SOA from smog chamber oxidation of indole by NO<sub>3</sub> in order to help identify peaks unique to nitroindole (<i>m</i>/<i>z</i> 162, 132, and 116). Quantum chemical calculations were done to determine the energetics of hypothesized indole + NO<sub>3</sub> intermediates and products. The combination of these data suggests a mechanism, wherein a hydrogen atom is first abstracted from the N–H bond in indole, followed by isomerization to a carbon-centered radical in the 3-position and followed by addition of NO<sub>2</sub>. Alternative mechanisms involving a direct abstraction of a H atom from a C–H bond or a NO<sub>3</sub> addition to the ring are predicted to be energetically unfavorable from large barriers for the initial reaction steps.","PeriodicalId":29796,"journal":{"name":"ACS Physical Chemistry Au","volume":null,"pages":null},"PeriodicalIF":3.7000,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Isomeric Identification of the Nitroindole Chromophore in Indole + NO3 Organic Aerosol\",\"authors\":\"Avery B. Dalton, Lisa M. Wingen, Sergey A. Nizkorodov\",\"doi\":\"10.1021/acsphyschemau.4c00044\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Oxidation of indole by nitrate radical (NO<sub>3</sub>) was previously proposed to form nitroindole, largely responsible for the brown color of indole secondary organic aerosol (SOA). As there are seven known nitroindole isomers, we used chromatographic separation to show that a single nitroindole isomer is produced in the indole + NO<sub>3</sub> reaction and definitively assigned it to 3-nitroindole by comparison with chromatograms of nitroindole standards. Mass spectra of aerosolized 3-nitroindole particles were recorded with an aerosol mass spectrometer and directly compared to mass spectra of SOA from smog chamber oxidation of indole by NO<sub>3</sub> in order to help identify peaks unique to nitroindole (<i>m</i>/<i>z</i> 162, 132, and 116). Quantum chemical calculations were done to determine the energetics of hypothesized indole + NO<sub>3</sub> intermediates and products. The combination of these data suggests a mechanism, wherein a hydrogen atom is first abstracted from the N–H bond in indole, followed by isomerization to a carbon-centered radical in the 3-position and followed by addition of NO<sub>2</sub>. Alternative mechanisms involving a direct abstraction of a H atom from a C–H bond or a NO<sub>3</sub> addition to the ring are predicted to be energetically unfavorable from large barriers for the initial reaction steps.\",\"PeriodicalId\":29796,\"journal\":{\"name\":\"ACS Physical Chemistry Au\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.7000,\"publicationDate\":\"2024-07-11\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"ACS Physical Chemistry Au\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.1021/acsphyschemau.4c00044\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"ACS Physical Chemistry Au","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1021/acsphyschemau.4c00044","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
Isomeric Identification of the Nitroindole Chromophore in Indole + NO3 Organic Aerosol
Oxidation of indole by nitrate radical (NO3) was previously proposed to form nitroindole, largely responsible for the brown color of indole secondary organic aerosol (SOA). As there are seven known nitroindole isomers, we used chromatographic separation to show that a single nitroindole isomer is produced in the indole + NO3 reaction and definitively assigned it to 3-nitroindole by comparison with chromatograms of nitroindole standards. Mass spectra of aerosolized 3-nitroindole particles were recorded with an aerosol mass spectrometer and directly compared to mass spectra of SOA from smog chamber oxidation of indole by NO3 in order to help identify peaks unique to nitroindole (m/z 162, 132, and 116). Quantum chemical calculations were done to determine the energetics of hypothesized indole + NO3 intermediates and products. The combination of these data suggests a mechanism, wherein a hydrogen atom is first abstracted from the N–H bond in indole, followed by isomerization to a carbon-centered radical in the 3-position and followed by addition of NO2. Alternative mechanisms involving a direct abstraction of a H atom from a C–H bond or a NO3 addition to the ring are predicted to be energetically unfavorable from large barriers for the initial reaction steps.
期刊介绍:
ACS Physical Chemistry Au is an open access journal which publishes original fundamental and applied research on all aspects of physical chemistry. The journal publishes new and original experimental computational and theoretical research of interest to physical chemists biophysical chemists chemical physicists physicists material scientists and engineers. An essential criterion for acceptance is that the manuscript provides new physical insight or develops new tools and methods of general interest. Some major topical areas include:Molecules Clusters and Aerosols; Biophysics Biomaterials Liquids and Soft Matter; Energy Materials and Catalysis