The photolysis of tetrahydrofuran and of some of its methyl derivatives at 185 nm

1980 ◽  
Vol 58 (24) ◽  
pp. 2819-2826 ◽  
Author(s):  
Nuray Klzilkilic ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Liquid Phase ◽  
Quantum Yield ◽  
Gas Phase ◽  
Carbonyl Compounds ◽  
Quantum Yields ◽  
Product Analysis ◽  
A Value ◽  
Steric Factors ◽  
Methyl Derivatives ◽  
Group 1

The uv photolysis of tetrahydrofuran, 1, 2-methyltetrahydrofuran, 2, cis-2,5-dimethyltetrahydrofuran, 3, trans-2,5-dimethyltetrahydrofuran, 4, and 2,2,5,5-tetramethyltetrahydrofuran, 5, has been investigated by product analysis in the liquid phase, and quantum yields have been determined. The photolysis of tetrahydrofuran itself was also studied in the gas phase at pressures ranging from 1 to 120 atm (pressurizing gas N2); and very little difference was found between the photolytic behaviour of the vapour at 120 atm and that of the liquid. The major products are in ail cases the cyclopropanes and the corresponding carbonyl compounds, as well as the olefinic alcohols and the carbonyl compounds that are isomeric with the starting material. These products are considered to be formed by the two major primary processes [i] and [ii].[Formula: see text]The cyclopropanes formed in reaction [i] retain some excess energy (apparently more than is needed to realize the trimethylene form), and in the photolysis of tetrahydrofuran vapour the hot cyclopropane rearranges to a considerable extent into propene. The propene to cyclopropane yield ratio falls strongly with increasing pressure, to a value of 0.065 at 120 atm. A similar value is observed in the liquid phase photolysis.The five-membered oxyl alkyl diradical from reaction [ii] is the likely intermediate in the cis-trans photoisomerization that is observable with the 2,5-dimethyltetrahydrofurans [Formula: see text]. The photolysis of these compounds also demonstrates that steric factors have a strong bearing on the course of the reaction, e.g. the quantum yield of methylcyclopropane from the cis compound is 0.22, vs. 0.08 from the trans compound.Molecular hydrogen is produced if the tetrahydrofurans carry hydrogen in α-position. Its production is enhanced if the α-position is shared with a methyl group (1 gives a hydrogen quantum yield of 0.07, 2 of 0.17, 3 of 0.27, 4 of 0.29, and 5 of zero).

CONDITIONS FOR THE PHOTOCHEMICAL NITRATION OF BENZENE

1965 ◽  
Vol 43 (6) ◽  
pp. 1714-1719 ◽  
Author(s):  
David L. Bunbury
Keyword(s):  
Liquid Phase ◽  
Quantum Yield ◽  
Nitrogen Dioxide ◽  
Gas Phase ◽  
Dark Reaction ◽  
Gas Phases

The reaction of benzene and nitrogen dioxide to produce nitrobenzene has been studied in the liquid and gas phases, in the dark, and with irradiation by light of 439 mμ and of 366 mμ. The concentration of NO2 in the liquid was varied from 0.08 to 1.6 moles/1 and in the gas from 0.0035 to 0.053 moles/1. No nitrobenzene was produced under any conditions in the liquid phase. Nitrobenzene is produced in the gas phase at high NO2 concentrations with irradiation by 366 mμ light. The quantum yield is 0.2. At 439 mμ the quantum yield is not more than 0.02. There is a very small dark reaction. As the concentration of NO2 in the gas is reduced the yield of nitrobenzene falls off very rapidly and is zero at the lowest concentration used, both in dark and light.

Excited radicals in the gas phase photolysis of butene isomers at different photon energies: energy distribution in reaction products

1978 ◽  
Vol 56 (20) ◽  
pp. 2630-2637 ◽  
Author(s):  
Guy J. Collin ◽  
Andrzej Więckowski
Keyword(s):  
Quantum Yield ◽  
Kinetic Energy ◽  
Energy Distribution ◽  
Gas Phase ◽  
Excess Energy ◽  
Pressure Effects ◽  
Quantum Yields ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Pressure Region

A systematic study of the pressure effects on the quantum yields of some products between 0.1 and 600 Torr (13 and 80 000 N m−2) was carried out in the 7.6 and 8.4 eV photolysis of normal, iso- and cis-2-butenes. The propylene quantum yield (s-C4H9* → C3H6 + CH3) decreased with the increase in the n-butene pressure and a good linearity of S/D (stabilization/decomposition) vs. pressure plot, over a broad pressure region, was observed. It is concluded that hydrogen atoms involved in the s-C4H9* radical formation are produced with a relatively narrow energy distribution. The slope of S/D vs. pressure lines decreased with the increase in photon energy, indicating the trend in the kinetic energy of the H-atoms.In the case of isobutene and cis-2-butene photolysis, the Stern–Volmer plots for allene formation were nonlinear. It is concluded that the formation of two different allene precursors is needed to account for this result. By the use of a simple RRK-type formalism we also conclude that the excess energy of the photon in the primary photoexcited butene molecules is far from being randomized before their fragmentation occurs.[Formula: see text]

Reactions of thiyl radicals. XII. Triplet mercury photosensitized decomposition of ethyl sulfide in the gas phase

1976 ◽  
Vol 54 (8) ◽  
pp. 1290-1295 ◽  
Author(s):  
Conrad S. Smith ◽  
Arthur R. Knight
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Quantum Yields ◽  
Second Step ◽  
Primary Process ◽  
Reaction Products ◽  
Process Comparison ◽  
Thiyl Radicals ◽  
Ethyl Radicals ◽  
High Sulfide

The triplet mercury photosensitized decomposition of ethyl sulfide vapour has been studied at 25 °C. The reaction products include C2H4 (Φ0 = 0.075), C2H6 (Φ0 = 0.043), C4H10 (Φ0 = 0.011), C2H5SH (Φ0 = 0.068), 4-methyl-3-thiahexane (Φ0 = 0.011), and C2H5SSC2H5 (Φ0 = 0.175). The overall decomposition quantum yield is 0.38 at high sulfide pressures. The initial decomposition gives principally ethyl radicals and ethylthiyl radicals; a second step which yields ethylene and ethanethiol may account for up to 20% of the primary process. Comparison of the direct and sensitized decompositions indicates that both likely originate in the triplet manifold of ethyl sulfide.Primary decomposition quantum yields have been accurately redetermined for the direct, 254 nm, photolysis of methyl sulfide (0.51), methylethyl sulfide (0.46), and ethyl sulfide (0.49).

THE LIQUID PHASE PHOTOLYSIS OF DIETHYL KETONE AND METHYL ETHYL KETONE

1958 ◽  
Vol 36 (2) ◽  
pp. 400-409 ◽  
Author(s):  
P. Ausloos
Keyword(s):  
Liquid Phase ◽  
Quantum Yield ◽  
Methyl Ethyl Ketone ◽  
Methyl Ethyl ◽  
Diethyl Ketone ◽  
Arrhenius Plots ◽  
Temperature Range ◽  
A Value ◽  
Recombination Reactions

The liquid phase photolysis of diethyl ketone has been studied in the temperature range from −35° to 95 °C. The CO quantum yield at 95 °C. was found to be close to unity. At 28 °C. decrease in intensity and addition of heptane led to a substantial increase of the CO and the ethane yields.The methyl ethyl ketone liquid phase photolysis at temperatures between 5° and 75 °C. led to the same observations. Arrhenius plots of RE/RB1/2[K] gave for both compounds a value of 5 kcal./mole.Gas phase studies in the temperature range of 0° to 60 °C. confirmed the low CO quantum yield reported previously and showed evidence for disproportionation and recombination reactions between ethyl and propionyl radicals.

THE PHOTOLYSIS OF ACETONE IN THE LIQUID PHASE: THE GASEOUS PRODUCTS

1955 ◽  
Vol 33 (8) ◽  
pp. 1304-1315 ◽  
Author(s):  
R. Pieck ◽  
E. W. R. Steacie
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
High Temperatures ◽  
Low Temperatures ◽  
Excited Molecule ◽  
Quantum Yields ◽  
Cage Effect ◽  
Gaseous Products ◽  
Ethane Formation ◽  
Liquid Acetone

An investigation has been made of the photolysis of liquid acetone in the temperature range from 55° to −25 °C. The quantum yields of all products are small, and decrease strongly with decreasing temperature. It is concluded that the low yields can be explained both on the basis of the 'cage effect', and by the deactivation of an excited molecule. At high temperatures and intensities the gaseous products can be accounted for on the assumption that radicals have escaped from the 'cage' and react analogously to the gas-phase mechanism. At low temperatures ethane formation in the 'cage' may be of importance.

Application of Disk Aerators to Recarbonation of Alkaline Wastewater from Wet Gasification of Carbide

1991 ◽  
Vol 24 (7) ◽  
pp. 277-284 ◽  
Author(s):  
E. Gomólka ◽  
B. Gomólka
Keyword(s):  
Carbon Dioxide ◽  
Liquid Phase ◽  
Gas Phase ◽  
Flue Gas ◽  
Carbonic Acid ◽  
Low Cost ◽  
Flue Gases ◽  
Carbon Dioxide Content ◽  
Patent Claim ◽  
Phase Dispersion

Whenever possible, neutralization of alkaline wastewater should involve low-cost acid. It is conventional to make use of carbonic acid produced via the reaction of carbon dioxide (contained in flue gases) with water according to the following equation: Carbon dioxide content in the flue gas stream varies from 10% to 15%. The flue gas stream may either be passed to the wastewater contained in the recarbonizers, or. enter the scrubbers (which are continually sprayed with wastewater) from the bottom in oountercurrent. The reactors, in which recarbonation occurs, have the ability to expand the contact surface between gaseous and liquid phase. This can be achieved by gas phase dispersion in the liquid phase (bubbling), by liquid phase dispersion in the gas phase (spraying), or by bubbling and spraying, and mixing. These concurrent operations are carried out during motion of the disk aerator (which is a patent claim). The authors describe the functioning of the disk aerator, the composition of the wastewater produced during wet gasification of carbide, the chemistry of recarbonation and decarbonation, and the concept of applying the disk aerator so as to make the wastewater fit for reuse (after suitable neutralization) as feeding water in acetylene generators.

Modeling of aerated upflow fixed bed reactors for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 85-92 ◽  
Author(s):  
J. Behrendt
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bulk Liquid ◽  
Initial Value ◽  
Fixed Bed Reactors ◽  
Number Of Cells

A mathematical model for nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

Theoretical analysis of counter-current absorption of a poorly soluble gas based on the PDE-AD model

1986 ◽  
Vol 51 (6) ◽  
pp. 1222-1239 ◽  
Author(s):  
Pavel Moravec ◽  
Vladimír Staněk
Keyword(s):  
Experimental Data ◽  
Liquid Phase ◽  
Gas Phase ◽  
Transfer Functions ◽  
Packed Bed ◽  
Packed Bed Column ◽  
Interfacial Transport ◽  
Gaseous Component ◽  
Poorly Soluble ◽  
Counter Current

Expression have been derived in the paper for all four possible transfer functions between the inlet and the outlet gas and liquid steams under the counter-current absorption of a poorly soluble gas in a packed bed column. The transfer functions have been derived for the axially dispersed model with stagnant zone in the liquid phase and the axially dispersed model for the gas phase with interfacial transport of a gaseous component (PDE - AD). calculations with practical values of parameters suggest that only two of these transfer functions are applicable for experimental data evaluation.

Sign in / Sign up

Export Citation Format

Share Document