Photochemistry of ketones in solution. 50. Fluorescence lifetimes of .beta.,.gamma.-unsaturated ketones. Structural dependence of rate constants for reaction and decay of singlet excited states

1976 ◽  
Vol 98 (16) ◽  
pp. 5025-5027 ◽  
Author(s):  
David I. Schuster ◽  
Jens Eriksen ◽  
Paul S. Engel ◽  
Mary A. Schexnayder
Keyword(s):  
Excited States ◽  
Rate Constants ◽  
Fluorescence Lifetimes ◽  
Unsaturated Ketones ◽  
Structural Dependence

Reduction of hexaammineruthenium(III) ions by a series of tris(polypyridyl)chromium(II) ions – Revisiting the Cr(NN)33+/2+ self-exchange rate

2001 ◽  
Vol 79 (7) ◽  
pp. 1124-1127 ◽  
Author(s):  
K Omar Zahir
Keyword(s):  
Exchange Rate ◽  
Excited States ◽  
Rate Constants ◽  
Driving Force ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Outer Sphere ◽  
Laser Flash ◽  
Exchange Rate Constant ◽  
Kinetics Of

The kinetics of the outer-sphere oxidation of Cr(NN)32+ ions (NN = 2,2'-bipyridine, 1,10-phenanthroline, and their substituted analogs) by hexaammineruthenium(III) was studied using laser flash photolysis. The Cr(NN)32+ ions were generated via the reductive quenching of the *Cr(NN)33+ excited states by oxalate ions or by H2edta2–. The second-order rate constants were found to vary with the driving force of the reaction. The rate constants increase from (7.1 ± 0.5) × 106 M–1 s–1 for Cr(5-Clphen)32+ to (2.6 ± 0.2) × 108 M–1 s–1 for Cr(4,7-Me2phen)32+. The self-exchange rate constant for the couple (Cr(NN)33+/2+) was calculated by applying Marcus cross relation to present and other known reactions of Cr(NN)3n+ ions, where n = 3 or 2 with various reactants and is estimated to be (6 ± 4) × 107 M–1 s–1.Key words: tris(polypyridyl)chromium(II)/(III) self-exchange rate, hexaammineruthenium(III), oxidation of Cr(NN)32+.

scholarly journals Dynamics of small molecules within the F127 PEO-PPO-PEO triblock copolymer gel and sol phases studied at the molecular scale

2022 ◽  
Author(s):  
Suma S. Thomas ◽  
Helia Hosseini-Nejad ◽  
Cornelia Bohne
Keyword(s):  
Excited States ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Supramolecular System ◽  
Quenching Rate ◽  
Naphthalene Derivatives ◽  
Decay Rate Constant ◽  
Triplet Excited States

The dynamics of naphthalene derivatives with different hydrophobicities bound to F127 polyethyleneoxide-polypropyleneoxide-polyethyleneoxide (PEO-PPO-PEO) micelles in the gel and sol phases were studied using a quenching methodology for the triplet excited states of the naphthalenes. Studies with triplet excited states probe a larger reaction volume than the volumes accessible when using fluorescent singlet excited states. The use of triplet excited states enables the determination of the dynamics between different compartments of a supramolecular system, which in the case of F127 micelles are the micellar core, the micellar corona and the aqueous phase. This report includes laser flash photolysis studies for the four naphthalene derivatives in the F127 gel and sol phases. The triplet excited states were quenched using the nitrite anion as the quenchers. The association and dissociation rate constants of the naphthalenes from the micelles and the quenching rate constants for the naphthalenes bound to the micelles were determines from the curved quenching plot (observed decay rate constant vs. nitrite concentration).

scholarly journals Aqueous Reactions of Organic Triplet Excited States with Atmospheric Alkenes

2018 ◽  
Author(s):  
Richie Kaur ◽  
Brandi M. Hudson ◽  
Joseph Draper ◽  
Dean J. Tantillo ◽  
Cort Anastasio
Keyword(s):  
Double Bond ◽  
Excited States ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Oxidation Potential ◽  
Water Soluble ◽  
Oxidation Products ◽  
Bond Dissociation ◽  
Alkyl Substitution ◽  
Triplet Excited States

Abstract. Triplet excited states of organic matter, a.k.a. triplets, are formed when brown carbon absorbs light. While triplets can be important photooxidants in atmospheric drops and particles (e.g., they rapidly oxidize phenols), very little is known about their reactivity toward many classes of organic compounds in the atmosphere. Here we measure the bimolecular rate constants of the triplet excited state of benzophenone (3BP*), a model species, with 17 water-soluble C3–C6 alkenes that have either been found in the atmosphere or are reasonable surrogates for identified species. Measured rate constants (kALK+3BP*) vary by a factor of 30 and are in the range of (0.24–7.5) × 109 M−1 s−1. Biogenic alkenes found in the atmosphere – e.g., cis-3-hexen-1-ol, cis-3-hexenyl acetate, and methyl jasmonate – react rapidly, with rate constants above 1 × 109 M−1 s−1. Rate constants depend on alkene characteristics such as the location of the double bond, stereochemistry, and alkyl substitution on the double bond. There is a reasonable correlation between kALK+3BP* and the calculated one-electron oxidation potential (OP) of the alkenes (R2 = 0.58); in contrast, rate constants are not correlated with bond dissociation enthalpies, bond dissociation free energies, or computed energy barriers for hydrogen abstraction. Using the OP relationship, we estimate aqueous rate constants for a number of unsaturated isoprene and limonene oxidation products with 3BP*: values are in the range of (0.080–1.7) × 109 M−1 s−1, with generally faster values for limonene products. Using our predicted rate constants, along with values for other reactions from the literature, we conclude that triplets are probably minor oxidants for isoprene and limonene-related compounds in cloudy or foggy atmospheres, except in cases where the triplets are very reactive.

Gas-phase reaction of two unsaturated ketones with atomic Cl and O3: kinetics and products

2015 ◽  
Vol 17 (18) ◽  
pp. 12000-12012 ◽  
Author(s):  
Jing Wang ◽  
Li Zhou ◽  
Weigang Wang ◽  
Maofa Ge
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Atmospheric Pressure ◽  
Phase Reaction ◽  
Unsaturated Ketones ◽  
Gas Phase Reaction

The rate constants and products for the reactions of atomic Cl and O3 molecule with 3-methyl-3-buten-2-one (MBO332) and 3-methyl-3-penten-2-one (MPO332) were determined in a 100 L Teflon chamber at 293 ± 1 K and atmospheric pressure.

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