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Structural Effects on Photochemistry and Reactivity of Criegee Intermediates and Organic Hydroperoxides
Structural Effects on Photochemistry and Reactivity of Criegee Intermediates and Organic Hydroperoxides
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260311091511.5
- ISBN
- 9798280759923
- DDC
- 530.7
- 저자명
- Zou, Meijun
- 서명/저자
- Structural Effects on Photochemistry and Reactivity of Criegee Intermediates and Organic Hydroperoxides / Meijun Zou
- 발행사항
- [Sl] : University of Pennsylvania, 2025
- 형태사항
- 1 electronic resource (371 pages)
- 주기사항
- Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
- 주기사항
- Advisors: Lester, Marsha I. Committee members: Baumgart, Tobias; Fakhraai, Zahra; Karsili, Tolga.
- 학위논문주기
- - Ph.D. : University of Pennsylvania, 2025.
- 초록/해제
- 요약Criegee intermediates (R₁R₂C=O⁺O⁻) are transient, zwitterionic carbonyl oxides formed during alkene ozonolysis. Their photochemistry and reactivity are strongly subject to the substituents (R₁, R₂) and conformational forms. This work investigates such structural effects through experimental and high-level theoretical approaches. The Criegee intermediates are studied under jet-cooled conditions using 10.5 eV vacuum ultraviolet (VUV) photoionization detection or under thermal conditions using multiplexed photoionization mass spectrometry (MPIMS), which enables simultaneous kinetic and product analyses. The ultraviolet-visible (UV-Vis) spectrum of the methyl-ethyl-substituted Criegee intermediate (MECI) is characterized on the strong π*← π transition via a ground-state depletion method. A large rate coefficient (298 K, 10 Torr) is also obtained for MECI bimolecular reaction with SO₂ leading to formation of SO₃. Systematic comparison between MECI and resonance-stabilized methyl vinyl ketone oxide demonstrates that the extended conjugation red-shifts the UV-Vis absorption and hinders the bimolecular reactivity with SO₂. The prototypical methyl-substituted Criegee intermediate (CH₃CHOO) has syn and anti conformations distinguished by the -CH₃ orientation relative to the terminal oxygen. MPIMS investigation reveals that anti-CH₃CHOO reacts barrierlessly with dimethylamine via a 1,2-insertion mechanism, while syn-CH₃CHOO remains unreactive. Infrared (IR) excitation of jet-cooled CH₃CHOO in the CH stretch overtone region induces rapid unimolecular decay of both conformers. The resultant IR-VUV ion-dip spectrum reveals dominant contribution of the syn-CH₃CHOO due to its greater stability and higher population. Organic hydroperoxides are also studied as key reactive species in atmospheric oxidation cycles. The 282 nm photodissociation dynamics of tert-butyl-, cyclopentyl-, and cyclohexyl-hydroperoxide are investigated using velocity map imaging to obtain the velocity and angular distributions of the OH products. The total kinetic energy release (TKER) distributions are bimodal with low-TKER components indicative of internal conversion to the ground electronic state prior to dissociation. The high-TKER components are consistent with an impulsive model arising from dissociation in the excited electronic state, but exhibit greater internal energy partitioning in the two cyclic systems where low-frequency ring vibrations are efficient energy sinks. Complementary theory provides insights into the isotropic angular distributions observed for the three systems.
- 언어주기
- English
- 일반주제명
- Physical chemistry
- 일반주제명
- Atmospheric chemistry
- 일반주제명
- Chemistry
- 키워드
- UV spectroscopy
- 기타저자
- University of Pennsylvania Chemistry
- 기본자료저록
- Dissertations Abstracts International. 86-12B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520260311091511.5
■006m o d
■007cr|nu||||||||
■020 ▼a9798280759923
■040 ▼aMiAaPQD▼beng▼cMiAaPQD▼erda
■082 ▼a530.7
■1001 ▼aZou, Meijun▼eauthor.
■24510▼aStructural Effects on Photochemistry and Reactivity of Criegee Intermediates and Organic Hydroperoxides ▼cMeijun Zou
■260 ▼a[Sl]▼bUniversity of Pennsylvania▼c2025
■264 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a1 electronic resource (371 pages)
■336 ▼atext▼btxt▼2rdacontent
■337 ▼acomputer▼bc▼2rdamedia
■338 ▼aonline resource▼bcr▼2rdacarrier
■500 ▼aSource: Dissertations Abstracts International, Volume: 86-12, Section: B.
■500 ▼aAdvisors: Lester, Marsha I. Committee members: Baumgart, Tobias; Fakhraai, Zahra; Karsili, Tolga.
■5021 ▼bPh.D.▼cUniversity of Pennsylvania▼d2025.
■520 ▼aCriegee intermediates (R₁R₂C=O⁺O⁻) are transient, zwitterionic carbonyl oxides formed during alkene ozonolysis. Their photochemistry and reactivity are strongly subject to the substituents (R₁, R₂) and conformational forms. This work investigates such structural effects through experimental and high-level theoretical approaches. The Criegee intermediates are studied under jet-cooled conditions using 10.5 eV vacuum ultraviolet (VUV) photoionization detection or under thermal conditions using multiplexed photoionization mass spectrometry (MPIMS), which enables simultaneous kinetic and product analyses. The ultraviolet-visible (UV-Vis) spectrum of the methyl-ethyl-substituted Criegee intermediate (MECI) is characterized on the strong π*← π transition via a ground-state depletion method. A large rate coefficient (298 K, 10 Torr) is also obtained for MECI bimolecular reaction with SO₂ leading to formation of SO₃. Systematic comparison between MECI and resonance-stabilized methyl vinyl ketone oxide demonstrates that the extended conjugation red-shifts the UV-Vis absorption and hinders the bimolecular reactivity with SO₂. The prototypical methyl-substituted Criegee intermediate (CH₃CHOO) has syn and anti conformations distinguished by the -CH₃ orientation relative to the terminal oxygen. MPIMS investigation reveals that anti-CH₃CHOO reacts barrierlessly with dimethylamine via a 1,2-insertion mechanism, while syn-CH₃CHOO remains unreactive. Infrared (IR) excitation of jet-cooled CH₃CHOO in the CH stretch overtone region induces rapid unimolecular decay of both conformers. The resultant IR-VUV ion-dip spectrum reveals dominant contribution of the syn-CH₃CHOO due to its greater stability and higher population. Organic hydroperoxides are also studied as key reactive species in atmospheric oxidation cycles. The 282 nm photodissociation dynamics of tert-butyl-, cyclopentyl-, and cyclohexyl-hydroperoxide are investigated using velocity map imaging to obtain the velocity and angular distributions of the OH products. The total kinetic energy release (TKER) distributions are bimodal with low-TKER components indicative of internal conversion to the ground electronic state prior to dissociation. The high-TKER components are consistent with an impulsive model arising from dissociation in the excited electronic state, but exhibit greater internal energy partitioning in the two cyclic systems where low-frequency ring vibrations are efficient energy sinks. Complementary theory provides insights into the isotropic angular distributions observed for the three systems.
■546 ▼aEnglish
■590 ▼aSchool code: 0175
■650 4▼aPhysical chemistry
■650 4▼aAtmospheric chemistry
■650 4▼aChemistry
■653 ▼aCriegee intermediates
■653 ▼aPhotodissociation
■653 ▼aReaction kinetics
■653 ▼aUV spectroscopy
■653 ▼aVelocity map imaging
■7102 ▼aUniversity of Pennsylvania▼bChemistry.▼edegree granting institution.
■7201 ▼aLester, Marsha I.▼edegree supervisor.
■7730 ▼tDissertations Abstracts International▼g86-12B.
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17356656▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
