Photoelectron photoion coincidence (PEPICO) spectroscopy could become a powerful tool for the time-resolved study of multi-channel gas phase chemical reactions. Toward this goal, we have designed and tested electron ion optics that form core new PEPICO spectrometer, utilizing simultaneous velocity map imaging both cations electrons, while also achieving good cation mass resolution through space focusing. These are combined with side-sampled, slow-flow reactor photolytic initiation gas-phase...

We investigated the simplest alkylperoxy radical, CH3OO, formed by reacting photolytically generated CH3 radicals with O2, using new combustion reactions followed photoelectron photoion coincidence (CRF-PEPICO) apparatus at Swiss Light Source. Modeling experimental mass-selected threshold spectrum Franck-Condon simulations including transitions to triplet and singlet cationic states yielded adiabatic ionization energy of 10.265 ± 0.025 eV. Dissociative photoionization CH3OO generates CH3+...

In this work we discuss the implementation of a flipped active learning classroom model in large general chemistry classes at University Nevada, Reno. The setup is detailed with survey results on student perception toward design course. Although our recommendations were originally tailored to online environment, was implemented an in-person class accommodating teaching after pandemic. We evaluate average final examination scores when traditional in-person, emergency remote teaching, online,...

For applications in aqueous media, sulfonated tetrahydrosalen (sulfosalan, HSS) was synthesized by sulfonation of fuming sulfuric acid. The Pd(II) complex this ligand, [Pd(HSS)], showed outstanding activity hydrogenation and redox isomerization allylic alcohols homogeneous solutions or aqueous–organic biphasic systems (for oct-1-en-3-ol TOF(hydrogenation) = 1580 h–1, TOF(redox isomerization) 400 h–1). DFT calculations revealed that H2 is activated heterolytically, resulting a Pd(II)–hydride...

Photoelectron Photoion Coincidence (PEPICO) spectroscopy holds the promise of a universal, isomer-selective, and sensitive analytical technique for time-resolved quantitative analysis bimolecular chemical reactions. Unfortunately, its low dynamic range ∼103 has largely precluded use this purpose, where at least 105 is generally required. This limitation due to false coincidence background common all experiments, especially high count rates. Electron/ion pairs emanating from separate...

We investigate the gas-phase photochemistry of enolone tautomer acetylacetone (pentane-2,4-dione) following S2(ππ*) ← S0 excitation at λ = 266 and 248 nm, using three complementary time-resolved spectroscopic methods. Contrary to earlier reports, which claimed study one-photon found OH CH3 as only important products, we detect 15 unique primary photoproducts demonstrate that five them, including CH3, arise solely by multiphoton excitation. assign products six photochemical channels show most...

The kinetics of the combustion-relevant reaction allyl radical, a-C3H5, with molecular oxygen has been studied in a flow tube reactor at vacuum ultraviolet (VUV) beamline Swiss Light Source storage ring, using CRF-PEPICO (Combustion Reactions Followed by Photoelectron Photoion Coincidence Spectroscopy) setup. ability to measure threshold photoelectron spectra enables background-free detection reactive species as well an isomer-specific analysis products. Allyl was generated direct...

With use of a Pd(II)-sulfosalan complex as water-soluble catalyst, we have developed an efficient synthesis biaryls via Suzuki–Miyaura cross-coupling in water under aerobic conditions. The water-insoluble target molecules were isolated by simple filtration analytical purity after washing with 0.01 M aqueous HCl (20 examples). In most cases, palladium contamination was below 5 ppm considered acceptable for active pharmaceutical ingredients. established method is scalable, reproducible, and...

Abstract New sulfonated tetrahydrosalen‐type ligands and their water‐soluble palladium(II) complexes have been synthesized. The catalyze the Sonogashira coupling (23 examples) of various aryl halides (including chloroarenes) with terminal alkynes, good to excellent conversions under mild conditions (80 °C, air, no Cu I cocatalyst) in aqueous–organic mixtures turnover frequencies up 2790 h −1 . Under optimized reaction minimize environmental contamination, diphenylacetylenes can be isolated...

The dissociative photoionization of internal energy selected diethyl ether ions was investigated by imaging photoelectron photoion coincidence spectroscopy. In a large, 5 eV range Et2O+ cations decay two parallel and three sequential channels, which can be modeled well using statistical theory. 0 K appearance energies the CH3CHOCH2CH3+ (H-loss, m/z = 73) CH3CH2O═CH2+ (methyl-loss, 59) fragment were determined to 10.419 ± 0.015 10.484 0.008 eV, respectively. reemergence hydrogen-loss ion...

The vacuum ultraviolet photoionization of the methyl peroxy radical, CH3O2, and unimolecular dissociation internal energy selected CH3O2+ cations were investigated in 9.7-12.0 eV range by synchrotron-based double imaging photoelectron photoion coincidence. A microwave discharge flow tube was employed to produce CH3O2 via reaction radicals (CH3) with oxygen gas. After identifying separating different sources CH3+ from CH3 or dissociative high resolution slow spectrum (SPES) obtained,...

The dissociation of energy-selected 1,3,5-cycloheptatriene (CHT) and toluene (Tol) cations was investigated by imaging photoelectron photoion coincidence spectroscopy. In the measured energy ranges 10.30-11.75 eV for CHT 11.45-12.55 Tol, only hydrogen atom loss channels open up, leading to C7H7+ from both molecular ions, which are metastable at H-loss threshold. Quantum chemical calculations showed that an interconversion ions happens below Therefore, a single statistical model constructed...

The unimolecular dissociation reactions of energy-selected furfural cations have been studied by imaging photoelectron photoion coincidence spectroscopy at the vacuum-ultraviolet (VUV) beamline Swiss Light Source. In photon energy range 10.9-14.5 eV, ions decay numerous fragmentation channels. Modeling breakdown diagram yielded 0 K appearance energies 10.95 ± 0.10, 11.16, and 12.03 eV for c-C4H3O-CO+ (m/z = 95), c-C4H4O+ 68), c-C3H3+ 39) fragment ions, respectively, formed parallel An...

The unimolecular dissociation of energy-selected ethylenediamine cations was studied by threshold photoelectron photoion coincidence spectroscopy (TPEPICO) in the photon energy range 8.60-12.50 eV. Modeling breakdown diagram and time-of-flight distributions with rigid activated complex RRKM theory yielded 0 K appearance energies for eight channels, leading to NH2CHCH2(+)(•) at 9.120 ± 0.010 eV, CH3C(NH2)2(+) 9.200 0.012 NH2CHCH3(+) 9.34 0.08 CH2NH2(+) 9.449 0.025 CH2NH3(+) 9.8 0.1...

PEPICO allows us a peek beyond the transition state to identify bifurcated reaction pathways.

The dissociative photoionization processes of methyl hydroperoxide (CH3OOH) have been studied by imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy experiments as well quantum-chemical and statistical rate calculations. Energy selected CH3OOH+ ions dissociate into CH2OOH+, HCO+, CH3+, H3O+ in the 11.4-14.0 eV photon energy range. lowest-energy dissociation channel is formation cation smallest "QOOH" radical, CH2OOH+. An extended RRKM model fitted to experimental data yields a...

Water-soluble salan ligands were synthesized by hydrogenation and subsequent sulfonation of salens (N,N’-bis(slicylidene)ethylenediamine analogues) with various bridging units (linkers) connecting the nitrogen atoms. Pd (II) complexes obtained in reactions sulfosalans [PdCl4]2−. Characterization included extensive X-ray diffraction studies, too. The proved highly active catalysts Suzuki–Miyaura reaction aryl halides arylboronic acid derivatives at 80 °C water air. A comparative study...

Abstract The dissociative photoionization of 1,3‐dioxolane was studied by photoelectron photoion coincidence (PEPICO) spectroscopy in the photon energy range 9.5–13.5 eV. Our statistical thermodynamics model shows that a total six dissociation channels are involved formation three fragment ions, namely, C 3 H 5 O 2 + ( m/z 73), 45), and 4 44), with two contributing to each. By comparing results ab initio quantum chemical calculations experimentally derived appearance energies most likely...

In this work we reflect on recent experiences in a large general chemistry lecture course while moving to online instruction right after spring break order prevent the spread of coronavirus disease 2019 at University Nevada, Reno. We analyze average examination scores across three semesters and percentages students choosing correct answers multiple-choice (MC) questions face-to-face environments. addition, provide ideas for instructors creating new MC show positive effect an active learning...

Abstract The reaction is performed with equimolar amounts of aryl iodide and terminal alkyne leading to full conversion upon sufficiently long times without a copper catalyst.