Laser flash photolysis investigations of diffusion-controlled reactions in supercritical fluids

1993 ◽  
Vol 97 (21) ◽  
pp. 5618-5623 ◽  
Author(s):  
Christopher B. Roberts ◽  
Jianwei Zhang ◽  
Joan F. Brennecke ◽  
John E. Chateauneuf
Keyword(s):  
Supercritical Fluids ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Diffusion Controlled

Direct detection of methylphenylgermylene and 1,2-dimethyl-1,2-diphenyldigermene — Kinetic studies of their reactivities in solution

2006 ◽  
Vol 84 (7) ◽  
pp. 934-948 ◽  
Author(s):  
William J Leigh ◽  
Ileana G Dumbrava ◽  
Farahnaz Lollmahomed
Keyword(s):  
Acetic Acid ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Direct Detection ◽  
Kinetic Studies ◽  
Laser Flash ◽  
Absolute Rate ◽  
Hydrocarbon Solvents ◽  
Diffusion Controlled

Photolysis of 1,3,4-trimethyl-1-phenylgermacyclopent-3-ene (5) in hydrocarbon solvents containing isoprene, methanol, or acetic acid affords 2,3-dimethyl-1,3-butadiene (DMB) and the expected trapping products of methyl phenylgermylene (GeMePh) in chemical yields exceeding 90%. The germylene has been detected in hexane solution by laser flash photolysis as a short-lived species (τ ~ 2 µs) exhibiting a UV-vis absorption spectrum centered at λmax = 490 nm. It decays with second-order kinetics and a rate constant close to the diffusion-controlled limit, with the concomitant growth of a second longer-lived transient (λmax = 420 nm) that is assigned to a mixture of (E)- and (Z)-1,2-dimethyl-1,2-diphenyldigermene (4). Absolute rate constants have been determined for the reactions of the germylene with primary and tertiary amines (n-BuNH2 and Et3N, respectively), acetic acid (AcOH), a terminal alkyne and alkene, isoprene, DMB, CCl4, and the group 14 hydrides Et3SiH and Bu3SnH. GeMePh is slightly more reactive than GePh2 towards all the reagents studied in this work; both are significantly less reactive than GeMe2 toward the same substrates. Absolute rate constants for the reactions of 4 have also been measured or assigned upper limits in every case and are compared to previously reported values for tetraphenyl- and tetramethyl-digermene with the same reagents.Key words: germylene, digermene, kinetics, laser flash photolysis, germirane, germirene, vinylgermirane, complex, UV–vis spectrum, insertion, addition.

scholarly journals Photoinduced oxidation of sea salt halides by aromatic ketones: a source of halogenated radicals

2009 ◽  
Vol 9 (2) ◽  
pp. 7681-7706 ◽  
Author(s):  
A. Jammoul ◽  
S. Dumas ◽  
B. D'Anna ◽  
C. George
Keyword(s):  
Triplet State ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Chemical Oxidation ◽  
Absorption Feature ◽  
Halide Anion ◽  
Oceanic Surface ◽  
Diffusion Controlled

Abstract. The interactions between benzophenone triplet state and halide anion species (Cl−, Br− and I−) have been studied by laser flash photolysis (at 355 nm) in aqueous solutions at room temperature. The decay of the triplet state of benzophenone was followed at 525 nm. Triplet lifetime measurements provided rate constants, kq (M−1 s−1), close to diffusion controlled limit for iodide (~8×109 M−1 s−1), somewhat less for bromide (~3×108 M−1 s−1) and much lower for chloride (>106 M−1 s−1). The halide (X−) quenches the triplet state, and a product, having a transient absorption at 355 nm and a lifetime much longer than that of the benzophenone triplet state, is formed. This transient absorption feature matches those of the corresponding radical anion (X2−). We therefore suggest that such reactive quenching can be a photosensitized source of halogen in the atmosphere and represents a driving force for the chemical oxidation of the oceanic surface.

scholarly journals New optical cell design for laser flash photolysis studies in supercritical fluids

1995 ◽  
Vol 66 (1) ◽  
pp. 222-226 ◽  
Author(s):  
Qin Ji ◽  
Edward M. Eyring ◽  
Rudi van Eldik ◽  
Kedika Bal Reddy ◽  
Steven R. Goates ◽  
...  
Keyword(s):  
Supercritical Fluids ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Cell Design ◽  
Optical Cell

The absolute kinetics for radical addition and electronic energy transfer to [1.1.1]propellane

1998 ◽  
Vol 76 (10) ◽  
pp. 1474-1489 ◽  
Author(s):  
P F McGarry ◽  
J C Scaiano
Keyword(s):  
Free Radicals ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Electronic Energy ◽  
Triplet States ◽  
Quenching Rate ◽  
Electronic Energy Transfer ◽  
Diffusion Controlled

Free radicals react more readily with [1.1.1]propellane, 1, than with styrene. For example Et3Si· reacts with 1 and styrene with rate constants of 6 × 108 M-1 s-1 and 2 × 108 M-1 s-1, respectively. Fluorenone, phenanthrene, triphenylene, benzophenone, and pyrene transfer electronic energy to 1 with rate constants well below the diffusion-controlled limit. For example, triplet benzophenone is quenched by 1 with a bimolecular rate constant of 9.9 × 106 M-1 s-1. A linear dependence of the log of the quenching rate constants, log kq, upon the excited-state energy of the donors is found.Key words: propellane, laser flash photolysis, free radicals, triplet states.

Reactivities of triarylmethyl and diarylmethyl cations with azide ion investigated by laser flash photolysis. Diffusion-controlled reactions

1991 ◽  
Vol 113 (3) ◽  
pp. 1009-1014 ◽  
Author(s):  
Robert A. McClelland ◽  
V. M. Kanagasabapathy ◽  
Narinder S. Banait ◽  
Steen Steenken
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Azide Ion ◽  
Diffusion Controlled
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