Photochemische 2+2-Cycloadditionen von Äthylen und Acetylen an 1.3-Cyclohexadien unter erhöhtem Druck / Photochemical 2+2-Cycloadditions of Ethylene and Acetylene to 1,3-Cyclohexadiene under High Pressure

1977 ◽  
Vol 32 (1) ◽  
pp. 47-52 ◽  
Author(s):  
Marlis F. Mirbach ◽  
Manfred J. Mirbach ◽  
Alfons Saus
Keyword(s):  
High Pressure ◽  
Quantum Yield ◽  
Room Temperature ◽  
Kinetic Scheme ◽  
Solvent Mixture ◽  
Experimental Results ◽  
Quantum Yields ◽  
Ethylene Pressure ◽  
Formal Kinetic

The photochemical cycloaddition of 1,3-cyclohexadiene (CHD) to ethylene and acetylene at pressures above 10 bar is described. Upon sensitized irradiation (2-acetylnaphthaline) CHD adds to ethylene at room temperature in dichloromethane to give cis-bicyclo[4,2,0]-oct-2-ene (1) along with dimers of cyclohexadiene. The yield of cross adduct increases with ethylene pressure (10-50 bar) whereas dimerisation decreases. Quantum yields of cross addition and dimerisation at 12 M ethylene were determined to be 0.31 and 0.35 respectively. At a pressure of 15 bar acetylene CHD reacts with acetylene to give bicyclo-[4,2,0]octa-2,7-diene (2) and bicyclo[2,2,2]octa-2,5-diene (3) as the major and minor products respectively. In a solvent mixture containing 60 vol-% CH2Cl2 and 40 vol-% acetone (2) is formed with a quantum yield of φ = 0.2. The experimental results are explained by a formal kinetic scheme.

The Quantum Yield of Oxidation of Hevea Rubber and GR-S

1948 ◽  
Vol 21 (3) ◽  
pp. 639-653 ◽  
Author(s):  
E. J. Hart ◽  
M. S. Matheson
Keyword(s):  
Quantum Yield ◽  
Room Temperature ◽  
Wave Length ◽  
Radical Reaction ◽  
Quantum Yields ◽  
Initial Reaction ◽  
Free Radical Reaction ◽  
Stable Intermediate ◽  
A Chain ◽  
Reaction Chain

Abstract The initial quantum yields of photoöxidation for purified Hevea rubber have been measured for various mercury arc lines in the wave length region 2537– 17,400 A˚. All experiments were carried out at room temperature and at an oxygen pressure of one atmosphere. At the outset of irradiation all quantum yields of combined oxygen are less than unity, although the quantum efficiency rises above 1.0 at 2537 and 3130 A˚. as photoöxidation proceeds. The low quantum yield suggests that in its initial stages (less than 0.1 per cent oxygen combined on the rubber) photoöxidation is not a chain reaction. It is postulated as the first step in rubber photoöxidation that the light activated rubber group reacts with oxygen to give a relatively stable intermediate which does not immediately dissociate to give a free radical reaction chain. The quantum yields of photoöxidation of purified GR-S were also measured under the same conditions as used for rubber. At each wave length the quantum yield was lower than for rubber, indicating formation of a stable intermediate in the initial reaction also.

Absolute Quantum Yields for Exciplex Fluorescence

1990 ◽  
Vol 44 (1) ◽  
pp. 101-105 ◽  
Author(s):  
S. J. Hale ◽  
L. A. Melton
Keyword(s):  
Quantum Yield ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Quantum Yields ◽  
Absolute Quantum Yield ◽  
The Absolute ◽  
Visualization Systems ◽  
Methyl Naphthalene ◽  
Absolute Quantum ◽  
Exciplex Fluorescence

The absolute quantum yields for exciplex fluorescence in four solutions which have potential as exciplex-based vapor/liquid visualization systems have been measured. The room-temperature absolute quantum yields for 10% dibutyl-aniline/0.4%, 1-cyanonaphthalene, 12.5% 1-methyl-naphthalene/0.5% N,N,N′,N′-tetramethyl- p-phenylenediamine (TMPD), 10% trihexylamine/1.0% 1-cyanonaphthalene, and 10% naphthalene/1.0% TMPD in hexadecane or cyclohexane are 0.03 ± 0.005, 0.05 ± 0.002 (308 nm), 0.02 ± 0.001, and 0.16 ± 0.021, respectively. The temperature dependence of the absolute quantum yield for the 10% naphthalene/1% TMPD in the hexadecane system was measured over the range of 23 to 260°C and was found to decrease by 20–30% at 260°C.

Strahlungslose Übertragung der Anregungsenergie in lumineszierenden Lösungen verschiedener Konzentrationsverhältnisse von Donor zu Akzeptor / Non-Radiative Excitation Energy Transfer in Luminescent Solutions at Different Ratios of Donor to Acceptor Concentration

1973 ◽  
Vol 28 (10) ◽  
pp. 1697-1702 ◽  
Author(s):  
C. Bojarski ◽  
F. Burak ◽  
E. Grabowska
Keyword(s):  
Energy Transfer ◽  
Quantum Yield ◽  
Excitation Energy ◽  
Acta Phys ◽  
Rhodamine B ◽  
Excitation Energy Transfer ◽  
Experimental Results ◽  
Quantum Yields ◽  
Full Agreement ◽  
Acceptor Concentration

Photoluminescence (PL) quantum yields (η/η0) of Na-fluoresceine (donor) in dependence on phloxin (acceptor) concentration in glycerin-water solutions at ratios of donor to acceptor concentration CD/CA equal to 48.2, 14.5 and 2.4 have been measured.Similar measurements have been made on acriflavine (donor) and rhodamine B (acceptor) in methanol for CD/CA = 10 and 0.4. In all systems investigated it was found that the PL-yield η/η0 of the donor at a fixed value of CA is the smaller the bigger is the value of CD/CA. The experimental results have been compared with a theory (Z. Naturforsch. 25 a, 1760 [1970], Acta Phys. Hung. 30, 145 [1971]) describing concentrational changes of the PL-quantum yield. Full agreement of theory with experiment is found and the possibility of multi-step non-radiative excitation energy transfer from donor to acceptor has been proved.

Low-temperature and high-pressure phases of a room-temperature ionic liquid and polyiodides: 1-methyl-3-propylimidazolium iodide

2018 ◽  
Vol 206 ◽  
pp. 49-60 ◽  
Author(s):  
Hiroshi Abe ◽  
Hiroaki Kishimura ◽  
Mayumi Takaku ◽  
Mai Watanabe ◽  
Nozomu Hamaya
Keyword(s):  
High Pressure ◽  
Ionic Liquid ◽  
Low Temperature ◽  
Amorphous Phase ◽  
Room Temperature ◽  
Room Temperature Ionic Liquid ◽  
Experimental Results

Experimental results are summarized on the P–T–m diagram. In pure [C3mim][I], amorphous phase appeared both at low-temperature and high-pressure. Stoichiometric [C3mim][I3] promotes crystallization, while non-stoichiometric [C3mim][I3.66] indicates anomalies.

Porewater in Compacted Water-Saturated MX-80 Bentonite

2012 ◽  
Vol 1475 ◽  
Author(s):  
Torbjörn Carlsson ◽  
Arto Muurinen ◽  
Michał Matusewicz ◽  
Andrew Root
Keyword(s):  
High Pressure ◽  
Experimental Evidence ◽  
Nuclear Fuel ◽  
Room Temperature ◽  
Spent Nuclear Fuel ◽  
Experimental Results ◽  
Interlayer Water ◽  
Proper Understanding ◽  
Buffer Material ◽  
Water Saturated

ABSTRACTBentonite is planned to be used in many countries as a buffer material in repositories for spent nuclear fuel. The proper understanding and modelling of the functioning of the water-saturated bentonite requires knowledge about the bentonite microstructure and also the way water is distributed between different phases. This paper presents experimental results from our studies of water in compacted, water-saturated MX-80 bentonite at dry densities in the range 0.7-1.6 g/cm3. Three techniques, Cl-porosity, SAXS and proton NMR measurements, were applied to samples kept at room temperature, while TEM imaging was applied to high pressure frozen samples. The combined results of these techniques strongly indicate that the two major water phases in the compacted MX-80 bentonite samples are ‘interlayer’ and ‘non-interlayer’ water. The results of the relative amounts of different water types by SAXS and NMR are very similar. The results by Cl-porosity measurement indicate that only part of the non-interlayer water is available for anions. Those observations are discussed in comparison to TEM micrographs. Our study provides solid experimental evidence for the presence of two major water phases in water-saturated bentonite and estimates their relative proportions and pore sizes.

Zur Anwendimg vpm Extinktionsdiagrammen bei der kinetischen Analyse von Photoreaktionen / Kinetic Analysis of Photochemical Reactions Using Extinction Diagrams

1972 ◽  
Vol 27 (11) ◽  
pp. 1354-1359 ◽  
Author(s):  
Heinz Mauser ◽  
Volker Starrock ◽  
Hans-Joachim Niemann
Keyword(s):  
Quantum Yield ◽  
Kinetic Analysis ◽  
Rate Constant ◽  
Extinction Coefficient ◽  
Photochemical Reactions ◽  
Experimental Results ◽  
Quantum Yields ◽  
Reaction Step ◽  
Consecutive Reaction ◽  
Consecutive Reactions

The reaction of anthraquinone in alkaline methanol irradiated with 313 nm light is followed spectrophotometrically. The experimental results point to an irreversible consecutive reaction A → B → C. Since the concentration and extinction coefficient of the intermediate are unknown, the partial quantum yield cannot be calculated. A new method is described for calculation of the concentration of the unknown intermediate using the extinction diagram. It is suitable for consecutive reactions, if the rate constant of the first reaction-step is very great as compared with that of the second. Now the partial quantum yields of the two reaction-steps can be calculated.

Fluorescence Quantum Yields of 2-Substituted 3-Methylquinoxalines in Liquid Solutions at Room Temperature

1991 ◽  
Vol 46 (8) ◽  
pp. 700-702
Author(s):  
A. Kawski ◽  
K. Nowaczyk ◽  
B. Kuklinski
Keyword(s):  
Quantum Yield ◽  
Fluorescence Spectra ◽  
Room Temperature ◽  
Atomic Weight ◽  
Modulation Method ◽  
Quantum Yields ◽  
Strong Decrease ◽  
Polar Solvents ◽  
Fluorescence Quantum Yields ◽  
Liquid Solutions

AbstractA sensitivity modulation method was employed to measure the fluorescence spectra and quantum yields of weakly fluorescent 2-substituted (NH2, O, OCH3, CI, Br) 3-methylquinoxalines in n-hexane and methanol at room temperature. A strong decrease in the quantum yield with increasing atomic weight of the substituents was observed in n-hexane. In polar solvents, the CI substituent is the strongest quencher although its atomic weight is 2.254 times smaller than that of Br

High-pressure freezing and freeze substitution of teliospores of the rust fungus Gymnosporangium clavipes

1990 ◽  
Vol 48 (3) ◽  
pp. 692-693
Author(s):  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Pathogenic Fungus ◽  
Rust Fungus ◽  
Freeze Substitution ◽  
Ice Crystals ◽  
High Pressure Freezing ◽  
Thin Walled Structures ◽  
Cytological Changes ◽  
Dextran Solution

The use of cryo-techniques for the preparation of biological specimens in electron microscopy has led to superior preservation of ultrastructural detail. Although these techniques have obvious advantages, a critical limitation is that only 10-40 μm thick cells and tissue layers can be frozen without the formation of distorting ice crystals. However, thicker samples (600 μm) may be frozen well by rapid freezing under high-pressure (2,100 bar). To date, most work using cryo-techniques on fungi have been confined to examining small, thin-walled structures. High-pressure freezing and freeze substitution are used here to analysis pre-germination stages of specialized, sexual spores (teliospores) of the plant pathogenic fungus Gymnosporangium clavipes C & P.Dormant teliospores were incubated in drops of water at room temperature (25°C) to break dormancy and stimulate germination. Spores were collected at approximately 30 min intervals after hydration so that early cytological changes associated with spore germination could be monitored. Prior to high-pressure freezing, the samples were incubated for 5-10 min in a 20% dextran solution for added cryoprotection during freezing. Forty to 50 spores were placed in specimen cups and holders and immediately frozen at high pressure using the Balzers HPM 010 apparatus.

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