Two channel competitive photodecomposition reaction of gaseous bromoethane at 193.1 nm

1983 ◽  
Vol 61 (11) ◽  
pp. 2486-2489 ◽  
Author(s):  
Kyung-Hoon Jung ◽  
Chong Mok Lee ◽  
Hee Soo Yoo
Keyword(s):  
Room Temperature ◽  
Vacuum Ultraviolet ◽  
Constant Pressure ◽  
Radical Reaction ◽  
Quantum Yields ◽  
Radical Scavenger ◽  
Reaction Products ◽  
Principal Reaction ◽  
Ultraviolet Photolysis ◽  
Pressure Independent

The vacuum ultraviolet photolysis of gas phase bromoethane at 193.1 nm (6.42 eV) was studied over the pressure range of 1.1–303.2 Torr at room temperature using a carbon atom lamp. The pressure effect with and without inert gas, i.e., He or N2, was investigated. A scavenger effect of the reaction was also observed by adding NO as a radical scavenger. The principal reaction products were C2H6, C2H4, 1,1-C2H4Br2, and n-C4H10. The quantum yields of C2H4 and C2H6 were found to increase slightly with the reactant pressure. When the pressure of He or N2 was varied at a constant pressure of C2H5Br, however, the quantum yields of C2H4 and C2H6 were found to be pressure independent. Addition of NO completely suppressed the formation of C2H6, C2H4Br2, and C4H10, and partially reduced that of C2H4. These results were interpreted in terms of two channel competition between the molecular elimination and the formation of radicals. Two different decomposition modes were 82% radical reaction and 18% molecular elimination.

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.

THE Hg 6(3P1) PHOTOSENSITIZATION OF CHLORODIFLUOROMETHANE

1965 ◽  
Vol 43 (5) ◽  
pp. 1022-1029 ◽  
Author(s):  
M. G. Bellas ◽  
O. P. Strausz ◽  
H. E. Gunning
Keyword(s):  
Incident Light ◽  
Strong Dependence ◽  
Quantum Yields ◽  
Primary Process ◽  
Reaction Products ◽  
Light Intensities ◽  
Principal Reaction ◽  
Bond Scission ◽  
Circulatory Apparatus ◽  
Cl Atoms

The reaction was studied in a circulatory apparatus under a variety of conditions. The sole primary process occurring is C—Cl bond scission. The Cl atoms formed in the primary step, through an abstractive attack on the substrate, generate chlorodifluoromethyl radicals (CF2Cl) All principal reaction products, CF2H2, CF2Cl2, CF2ClCF2Cl, CF2HCF2H, and CF2HCF2Cl, can be accounted for by the combination–disproportionation reactions of the CF2H• and CF2Cl• radicals. The observed strong dependence of the primary quantum yields on the incident light intensities has been ascribed to a rapid substrate-reforming step.

Primary Processes in the Vacuum Ultraviolet Photolysis of Ethyl Fluoride at 147 nm

1972 ◽  
Vol 50 (10) ◽  
pp. 1443-1447 ◽  
Author(s):  
S. C. Chan ◽  
Y. Inel ◽  
E. Tschuikow-Roux
Keyword(s):  
Energy Transfer ◽  
Pressure Dependence ◽  
Room Temperature ◽  
Vacuum Ultraviolet ◽  
Photochemical Reactions ◽  
Energy Transfer Efficiency ◽  
Gas Pressure ◽  
Inert Gas ◽  
Ultraviolet Photolysis ◽  
Ethyl Fluoride

The photolysis of C2H5F at 147 nm was studied at room temperature. The principal products include C2H3F, C2H2, C2H4, CH4, and C2H6. The principal primary photochemical reactions involve the molecular elimination of HF and H2, and, to a lesser extent, C—F and C—C bond fission. The effect of reactant and added inert gas pressure on the product yields has been investigated and it was found that the stabilization/decomposition ratio, C2H4/C2H2, displays opposite pressure dependence with ethyl fluoride and argon. This result is interpreted in terms of the higher energy transfer efficiency of the C2H5F molecule.

The Vacuum Ultraviolet Photolysis of Cyclopentanone

1972 ◽  
Vol 50 (24) ◽  
pp. 3938-3943 ◽  
Author(s):  
Alfred A. Scala ◽  
Daniel G. Ballan
Keyword(s):  
Quantum Yield ◽  
Carbonyl Group ◽  
Incident Energy ◽  
Vacuum Ultraviolet ◽  
Quantum Yields ◽  
Electronically Excited ◽  
Ultraviolet Photolysis

In the vacuum ultraviolet photolysis of cyclopentanone, the major modes of fragmentation of the electronically excited ketone are:[Formula: see text]The sum of the quantum yields for reactions A and B is 0.87 at 147.0 nm and these reactions become less important as the incident energy is increased. A pressure study at 147.0 nm of the partitioning of the tetramethylene diradical between paths A and B indicates that the ratio kA/kB is approximately 8. The quantum yield for reaction 8 is only 0.02. The remainder of the decomposition of cyclopentanone is accounted for by reactions 4 and 5, which appear to become more significant as the incident energy increases. The mechanisms for reactions 6 and 8 are best interpreted in terms of diradicals of structure (CH2)n where n = 1, 3, and 4. The lack of non-acyl σ-cleavage at 147.0 nm is an indication that the absorption of energy occurs at the carbonyl group.

Flash photolysis of carbon suboxide: absolute rate constants for reactions of C( 3 P) and C( 1 D) with H 2 , N 2 , CO, NO, O 2 and CH 4

1969 ◽  
Vol 312 (1510) ◽  
pp. 417-434 ◽  
Keyword(s):  
Rate Constants ◽  
Room Temperature ◽  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Spectroscopic Method ◽  
Reaction Rates ◽  
Reaction Scheme ◽  
Minor Importance ◽  
Primary Products ◽  
Pressure Independent

The vacuum ultraviolet flash photolysis of C 3 O 2 in the 159.0 nm absorption band has been investigated. The major primary products are C( 1 S), C( 1 D), C( 3 P), and CO. The species C 2 and C 3 have also been observed but are of minor importance in the overall reaction scheme. A number of pressure independent reactions involving C( 3 P), C( 1 D), and C( 1 S) with CO, CH 4 , N 2 , NO, O 2 , and H 2 have been observed by means of the kinetic-spectroscopic method. The rate constants measured at room temperature are summarized here (cm 3 s -1 molecule -1 ): C( 3 P) + CH 4 → C 2 H 4 (?) k < 5 x 10 -15 (7) C( 1 D) + CH 4 → C 2 H 2 + H 2 k = 3.2 x 10 -11 (8) C( 1 D) + N 2 → C( 3 P) + N 2 k ≈ 2.5 x 10 -12 (10) C( 3 P) + NO → CN + O k = 1.1 x 10 -10 (12) C( 1 D) + NO → CN + O k = 9.2 x 10 -11 (13) C( 1 D) + H 2 → CH + H k = 4.15 x 10 -11 (18) C( 1 S) + H 2 → CH + H(?) k < 5 x 10 -12 (19) C( 3 P ) + O 2 → CO + O k = 3.3 x 10 -11 (20) C( 1 D) + O 2 → CO + O(?) k < 5 x 10 -12 (22) The pressure dependent reaction rates of C( 3 P) with N 2 , CO, and H 2 have been qualitatively measured and are discussed in detail.

Piezoresistivity and Electrical Resistance Relaxation of Polyisoprene Nanostructured Carbon Allotrope Hybrid Composites

2015 ◽  
Vol 1117 ◽  
pp. 52-55
Author(s):  
Artis Linarts ◽  
Maris Knite
Keyword(s):  
Electrical Resistance ◽  
Room Temperature ◽  
Constant Pressure ◽  
Hybrid Composites ◽  
Conductive Filler ◽  
Force Sensor ◽  
Filler Concentration ◽  
Nanostructured Carbon ◽  
Carbon Allotrope ◽  
Resistance Relaxation

Polymer conductive filler composites are believed to be promising materials for flexible force sensor manufacture. Polyisoprene various carbon allotrope hybrid composites were made and their piezoresistive properties depending on the two type’s filler concentration and their ratio have been determined. Electrical resistance relaxations of hybrid composites at constant pressure in room temperature were determined as well. Experimental data of resistance relaxation was analyzed and fitted similarly to stress relaxation of polymers at constant pressure.

On the Chemistry of Tetrabenzyl Thiuram Disulfide and Tetramethyl Thiuram Disulfide with Bis (Triethoxysilylpropyl) Tetrasulfide in Silica Compounds

2003 ◽  
Vol 76 (4) ◽  
pp. 876-891 ◽  
Author(s):  
R. N. Datta ◽  
A. G. Talma ◽  
S. Datta ◽  
P. G. J. Nieuwenhuis ◽  
W. J. Nijenhuis ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Succinic Anhydride ◽  
Dynamic Properties ◽  
The Other ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Negative Effect ◽  
Higher Temperature ◽  
Analytical Tools

Abstract The use of thiurams such as Tetramethyl thiuram disulfide (TMTD) or Tetrabenzyl thiuram disulfide (TBzTD) has been explored to achieve higher cure efficiency. The studies suggest that a clear difference exists between the effect of TMTD versus TBzTD. TMTD reacts with Bis (triethoxysilylpropyl) tetrasulfide (TESPT) and this reaction can take place even at room temperature. On the other hand, the reaction of TBzTD with TESPT is slow and takes place only at higher temperature. High Performance Liquid Chromatography (HPLC) with mass (MS) detection, Nuclear Magnetic Resonance Spectroscopy (NMR) and other analytical tools have been used to understand the differences between the reaction of TMTD and TESPT versus TBzTD and TESPT. The reaction products originating from these reactions are also identified. These studies indicate that unlike TMTD, TBzTD improves the cure efficiency allowing faster cure without significant effect on processing characteristics as well as dynamic properties. The loading of TESPT is reduced in a typical Green tire compound and the negative effect on viscosity is repaired by addition of anhydrides, such as succinic anhydride, maleic anhydride, etc.

scholarly journals The behaviour of visual purple at low temperature

1941 ◽  
Vol 179 (977) ◽  
pp. 151-159 ◽  
Keyword(s):  
Aqueous Solution ◽  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Absorption Curve ◽  
Quantum Yields

Visual purple is soluble and stable in a mixture of glycerol and water (3:1). At room temperature the spectrum of such a solution is identical with that of the aqueous solution. At — 73° C the peak of the absorption curve is higher and narrower than at room temperature, and it is shifted towards longer waves. The product of photodecomposition at — 73° C has a spectrum in ­ dependent of pH and is at low temperatures thermostable and photostable, but at room temperature it decomposes therm ally to indicator yellow. The primary product appears to be identical with transient orange. The quantum yields of the photoreaction at low and at room temperature are of the same order.

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