A5028808277- Chemical Reactions and Mechanisms
- Photochemistry and Electron Transfer Studies
- Crystallography and molecular interactions
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Synthesis and Catalytic Reactions
- Radical Photochemical Reactions
- Photochromic and Fluorescence Chemistry
- Organic Chemistry Cycloaddition Reactions
- Conducting polymers and applications
- Synthesis and Biological Evaluation
- Epoxy Resin Curing Processes
- Advanced Battery Materials and Technologies
- Energetic Materials and Combustion
- Chemistry and Chemical Engineering
- Photopolymerization techniques and applications
- Chemical Reactions and Isotopes
- Supercapacitor Materials and Fabrication
- Mass Spectrometry Techniques and Applications
- Chemical Reaction Mechanisms
- Advanced Chemical Physics Studies
- Cyclization and Aryne Chemistry
- Advanced Polymer Synthesis and Characterization
- Porphyrin and Phthalocyanine Chemistry
University of Cincinnati
2010-2023
Missouri University of Science and Technology
2015
University of Peradeniya
2007
When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with release N2. Mechanistic studies using laser flash photolysis, supported quantum calculations, show that each degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, three compounds distinct...
Photolysis of 1 in argon-saturated acetonitrile yields 2, whereas oxygen-saturated small amounts benzoic acid and benzamide are formed addition to 2. Similarly, photolysis 2 results a trace amount 3, the major product is formation benzamide. Laser flash an absorption due triplet vinylnitrene 4 (broad with λ(max) at 360 nm, τ = 1.8 μs, acetonitrile) that rate constant 1.2 × 10(7) s(-1) decays 5.6 10(5) s(-1). likewise but also ylide 5 (λ(max) 440 13 μs). The for forming 1.6 In acetonitrile,...
ABSTRACT Moisture in polymerization of a cationically cured silicone epoxy monomer blend is an important parameter that affects the resulting polymer properties. We report kinetics cationic monomers as function water concentration, directly quantified using Karl Fischer (KF) titration was characterized Fourier transform infrared (FTIR) spectroscopy and also mechanical strength polymers via diametral tensile measurements. Methodology results for material were compared with same methodology...
The irradiation of trans-vinylketones 1a–c yields the corresponding cis isomers 2a–c. Laser flash photolysis 1a and 1b with 308 355 nm lasers results in their triplet ketones (T1K 1), which rearrange to form 1,2-biradicals 3a 3b, respectively, whereas a 266 laser produces cis-isomers through singlet reactivity. Time-resolved IR spectroscopy confirmed that 2a is formed within pulse. In comparison, 1c showed only formation 2c At cryogenic temperatures, 1 also resulted 2. DFT calculations were...
Photolysis of 1 in chloroform yielded 2 as the major product and a small quantity 3. Laser flash photolysis demonstrated that upon irradiation, first excited triplet state ketone (T(1K)) is formed decayed to form radical 4, which has λ(max) at 380 nm (τ = μs). Radical 4 expelled nitrogen molecule yield imine 5 (λ(max) 300 nm). Density functional theory (DFT) calculations showed transition barrier for formation approximately kcal/mol. In comparison, argon matrices resulted nitrene 6, was...
To clarify the cis-trans isomerization mechanism of simple alkenes on triplet excited state surface, photochemistry acyclic and cyclic vinyl ketones with a p-methoxyacetophenone moiety as built-in sensitizer (1 2, respectively) was compared. When irradiated, ketone 1 produces its cis-isomer, whereas 2 does not yield any photoproducts. Laser flash photolysis yields transient spectrum λmax ∼ 400 nm (τ 125 ns). This is assigned to first (T1) 1, which presumably decays form biradical (1BR) that...
Nanosecond laser flash photolysis of o-hydroxyacetophenone (1a) and 2,4-dihydroxyacetophenone (1b) in ethanol acetonitrile results absorption due to triplet biradicals 2a (λmax 430 nm, τ ≈ 3 μs) 2b 400 1 μs), respectively. Triplet biradical intersystem crosses form Z-3a 10 whereas forms both Z-3b E-3b 350 5 72 μs). Quenching studies demonstrate that 3a,b are formed on the singlet excited surface 1a 1b. In at 77 K, derivatives 1b show phosphorescence, as is typical for ketones with (n,π*)...
Photolysis of p- and m-azidomethylacetophenone (1a, 1b) in argon-saturated solutions yields predominantly imine 2a, 2b, whereas irradiation 1a, 1b oxygen-saturated results heterocycles 3a, 3b, aldehydes 4a, 4b nitriles 5a, 5b. Density functional theory calculations place the energy first second excited state triplet ketones (T1K T2K) close proximity to each other. The transition for cleaving C–N bond form azido benzyl radicals 1aB, 1bB is located only 3 kcal mol–1 (1 = 4.184 kJ) above T1K,...
Excited-state intramolecular hydrogen transfer on the triplet surface of salicylideneaniline derivatives has received much less attention than corresponding ultrafast process singlet surface. To enhance understanding this reactivity, photochemical properties a series salicylidene-α-hydroxy acid salts with different substituents phenol moiety (1-3) were characterized. UV/vis absorption and phosphorescence measurements in ethanol revealed that 1-3 exist as both enol keto tautomers, form being...
Laser flash photolysis of cyclopropyl(phenyl)methanone 6 in argon‐saturated methanol yields the triplet ketone (T 1K ) that is formed with a rate constant ~1.7 × 10 7 s −1 ( λ max = 360 nm) and has lifetime ~1.4 µs. T decays to form ketyl radical ~300 nm), which dimerizes photoproducts, pinacol derivatives 8 9. In comparison, trans ‐phenyl(2‐phenylcyclopropyl)methanone 1 chloroform‐d results cis 2 smaller amount 3, presumably through 1,3‐biradical 11. Nanosecond laser does not reveal...
Laser flash photolysis, phosphorescence and density functional calculations were used to characterize the triplet excited states of phenylethanol derivatives 1, 2, 3 4. In acetonitrile, these alcohols formed with rate constants on order ~10 7 s –1 decayed between 10 5 6 . The energies 80 83 kcal/mol. Furthermore, can be as a sensitizer for alkyl azides form nitrene intermediates. Copyright © 2011 John Wiley & Sons, Ltd.
Abstract Review: solution and solid‐state reactivity of triplet alkyl nitrenes in photolysis azidoalkanes; 100 refs.