THE PHOTOCHEMICAL DECOMPOSITION OF METHYL AZIDE

1963 ◽  
Vol 41 (6) ◽  
pp. 1552-1559 ◽  
Author(s):  
C. L. Currie ◽  
B. deB. Darwent
Keyword(s):  
Quantum Yield ◽  
Vapor Phase ◽  
Gaseous Product ◽  
Short Chain ◽  
Excited Species ◽  
Photochemical Decomposition

The photolysis of methyl azide has been investigated in the vapor phase at low conversions and over suitable ranges of pressure, temperature, intensity, and wavelength. Under all conditions the principal gaseous product was N2 with small amounts of H2 (5–11%), and traces of CH4, C2H4, and C2H6. A condensate identified as (CH3N)x was also found.The quantum yield for the production of N2 is approximately 2, independent of intensity (over a 45-fold range), temperature (17–100 °C), and pressure (14–300 mm Hg). The quantum yield decreases slightly with increasing wavelength. Experiments with added CO2, CH3N2CH3, and C2H4 indicate the presence of a short chain carried mainly by the CH3N radical. Excited species probably play some role in the reaction.

The photochemical and thermal decompositions of hydrogen sulphide

1953 ◽  
Vol 216 (1126) ◽  
pp. 344-361 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Quantum Yield ◽  
Hydrogen Sulphide ◽  
Low Temperatures ◽  
Room Temperature ◽  
Large Fraction ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Photochemical Decomposition ◽  
Bimolecular Mechanism

The photochemical decomposition of hydrogen sulphide has been investigated at pressures between 8 and 550 mm of mercury and at temperatures between 27 and 650° C, using the narrow cadmium line ( λ 2288) and the broad mercury band (about λ 2550). At room temperature the quantum yield increases with pressure from 1.09 at 30 mm to 1.26 at 200 mm. Above 200 mm pressure there was no further increase in the quantum yield. Temperature had little effect on the quantum yield at λ 2550, but there was a marked increase in the rate of hydrogen production between 500 and 650° C with 2288 Å radiation. This may have been caused by the decomposition of excited hydrosulphide radicals. The results are consistent with a mechanism involving hydrogen atoms and hydrosulphide radicals. The mercury-photosensitized reaction is less efficient than the photochemical decomposition, the quantum yield being only about 0.45. The efficiency increased with temperature and approached unity at high temperatures and pressures. This agrees with the suggestion that a large fraction of the quenching collisions lead to the formation of Hg ( 3 P 0 ) atoms. The thermal decomposition is heterogeneous at low temperatures and becomes homogeneous and of the second order at 650° C. The experimental evidence suggests the bimolecular mechanism 2H 2 S → 2H 2 + S 2 . The activation energies are 25 kcal/mole (heterogeneous) and 50 kcal/mole (homogeneous).

Mechanism of the Direct Photochemical Decomposition of Thietane and its Derivatives in the Vapor Phase, in Solution, and in Glassy Matrices

1975 ◽  
Vol 53 (12) ◽  
pp. 1744-1755 ◽  
Author(s):  
David R. Dice ◽  
Ronald P. Steer
Keyword(s):  
Low Temperature ◽  
Gas Phase ◽  
Vapor Phase ◽  
Low Temperatures ◽  
Condensed Media ◽  
Photochemical Decomposition ◽  
Glassy Matrices

The direct photolyses of thietane, 3-ethyl-2-propylthietane, and 3-methylthietane in the vapor phase, in solution, and in glassy matrices at low temperatures have been examined. The effects of varying the photolysis wavelength, the temperature, the pressure and the phase of the substrate, and of adding inert thermalizers on the nature and yields of the various products have been measured. The results are interpreted in terms of initial C—S cleavage to give a 1,4-biradical which may, in the gas phase, decompose or ring close before complete equilibration of the various rotamers is achieved, or which may be thermalized in condensed media and trapped in glassy matrices at low temperature.

Photochemical decomposition of environmentally persistent short-chain perfluorocarboxylic acids in water mediated by iron(II)/(III) redox reactions

Chemosphere ◽  
2007 ◽  
Vol 68 (3) ◽  
pp. 572-578 ◽  
Author(s):  
Hisao Hori ◽  
Ari Yamamoto ◽  
Kazuhide Koike ◽  
Shuzo Kutsuna ◽  
Issey Osaka ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Short Chain ◽  
Perfluorocarboxylic Acids ◽  
Photochemical Decomposition

scholarly journals Determination of Quantum Yield for the Photochemical Decomposition of Dichloramine-B and Dibromamine-B in Aqueous Acetic Acid Medium

2007 ◽  
Vol 4 (4) ◽  
pp. 502-509
Author(s):  
K. N. Mohana ◽  
N. Prasad ◽  
P. M. Ramadas Bhandarkar
Keyword(s):  
Acetic Acid ◽  
Quantum Yield ◽  
Uv Light ◽  
Incident Light ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Rate Law ◽  
Photochemical Decomposition ◽  
Photolytic Decomposition

The photolysis of dihaloamines (RNX2),viz., dichloramine-B (DCB) and dibromamine-B (DBB) in aqueous acetic acid (1:1 v/v) solutions has been studied with the UV light source (λ= 2537 Å). The experimental rate law obtained is - d [RNX2] / dt = k' Io/ [RNX2], where Iois the intensity of incident light. The addition of benzenesulphonamide, the product of photolysis or uranyl ion had no significant effect on the rate of photochemical decomposition. A slight decrease in the rate has been observed by the addition of NaCl / NaBr to DCB / DBB solutions. The quantum yield (Φ) for the photolytic decomposition has been computed. A suitable photolytic mechanism and a rate law consistent with the observed results have been proposed.

The photolysis of ozone by ultraviolet radiation. I. The photolysis of pure, dry ozone

1965 ◽  
Vol 288 (1413) ◽  
pp. 200-211 ◽  
Keyword(s):  
Reaction Mechanism ◽  
Quantum Yield ◽  
Light Intensity ◽  
Ultraviolet Radiation ◽  
Oxygen Molecule ◽  
Inert Gases ◽  
Ozone Variation ◽  
Photochemical Decomposition ◽  
A Chain ◽  
Limiting Value

The photochemical decomposition of dry ozone has been studied at λ = 2537 Å. The quantum yield for the photolysis of pure ozone was proportional to the pressure of ozone; the highest quantum yield recorded was 16.7 at a pressure of 5 cmHg ozone. Variation of light intensity did not markedly affect the quantum yield, and some evidence was found for a wall termination reaction. A reaction mechanism is proposed in which O( 1 D ) atoms, formed in the primary photolysis, initiate a chain propagated by energy-rich oxygen molecules. A discussion of the nature of the energy-rich molecules is presented. Addition of inert gases to the pure ozone reduces the quantum yield to a limiting value of two. This is explained in terms of the deactivation of the energy-rich oxygen molecule. In the presence of oxygen, the quantum yield tends to zero, as a result of the reverse reaction O + O 2 + M → O 3 + M .

The photochemical decomposition of t -butyl hydroperoxide in solution

1953 ◽  
Vol 220 (1142) ◽  
pp. 322-339 ◽  
Keyword(s):  
Quantum Yield ◽  
Wave Length ◽  
Butyl Alcohol ◽  
Quantum Yields ◽  
Oxidation Reactions ◽  
Butyl Hydroperoxide ◽  
Acetone Water ◽  
Photochemical Decomposition ◽  
Solvent Molecules ◽  
A Chain

The photochemical decomposition of t -butyl hydroperoxide by light of wave-length 3130 Å has been investigated in three solvents. Reaction mechanisms are elucidated by consideration of the products and the quantum yields of decomposition. In carbon tetrachloride a chain reaction occurs in which the quantum yield of 3.2 at 20° C increases to 5.3 at 50° C. The main products are t -butyl alcohol and oxygen with smaller amounts of acetone, water and compounds arising from the oxidation of methyl radicals. The same series of reactions takes place in n -hexane, but superimposed are oxidation reactions involving solvent molecules which ultimately lead to the formation of alcohols. The quantum yield in this solvent is 3.9 and independent of temperature. When the peroxide is irradiated in dioxan solution immediate hydrogenation of the radicals produced in the primary photo-chemical act prevents the formation of reaction chains and the quantum yield is unity. The interaction of the radicals with solvent molecules is such that some of the etheric oxygen of the dioxan is transformed into alcoholic hydroxyl during the course of the reaction, and the fragmentation of dioxan gives formaldehyde Experiments with a dioxan solution using light of wave-length 2450 to 2800 Å show no fundamental change in the mode of decomposition of the peroxide, but an increase in concentration of the products of dioxan decomposition indicates a more vigorous attack by the radicals on the solvent.

Photosensitization by Cd(3P1) Atoms. II. Gas Phase Decomposition of Cyclohexane

1972 ◽  
Vol 50 (13) ◽  
pp. 2010-2016 ◽  
Author(s):  
B. L. Kalra ◽  
A. R. Knight
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Vapor Phase ◽  
Exposure Time ◽  
Molecular Hydrogen ◽  
Primary Decomposition ◽  
Phase Decomposition ◽  
Hydrogen Atoms ◽  
Hydrogen Formation ◽  
Volatile Products

The photodecomposition of cyclohexane sensitized by Cd(3P1) atoms has been studied in the vapor phase at 355 °C. The primary decomposition gives hydrogen atoms and cyclohexyl radicals. The volatile products of the decomposition are H2, cyclohexene, propylene, ethane, ethylene, methane, propane, butadiene, and methylcyclopentane. Products other than H2 and cyclo-C6H10 arise from unimolecular reactions of cyclohexyl radicals, the most important such process being the production of propylene and allyl radicals. Hydrogen yields decrease rapidly with time because of H-atom scavenging reactions involving olefinic products. The quantum yield of molecular hydrogen formation at the shortest exposure time examined is 0.53.

Sign in / Sign up

Export Citation Format

Share Document