CLXXXIX.—The conditions of reaction of hydrogen with sulphur. Part II. The catalytic effect of oxygen. Part III. The mechanism of the reaction of hydrogen with sulphur and its catalysis by oxygen

1923 ◽  
Vol 123 (0) ◽  
pp. 1689-1705 ◽  
Author(s):  
Ronald George Wreyford Norrish ◽  
Eric Keightley Rideal
Keyword(s):  
Catalytic Effect ◽  
Effect Of Oxygen ◽  
Mechanism Of The Reaction

Radical reactions of p-nitrobenzylidene halides with aci-nitronate ions

1978 ◽  
Vol 31 (11) ◽  
pp. 2477 ◽  
Author(s):  
DJ Freeman ◽  
RK Norris ◽  
SK Woolfenden
Keyword(s):  
Nitrous Acid ◽  
Catalytic Effect ◽  
Lithium Salt ◽  
Phase Transfer ◽  
Hydrogen Bromide ◽  
Radical Reactions ◽  
Radical Process ◽  
Tetrabutylammonium Salt ◽  
Effect Of Oxygen ◽  
Radical Processes

The radical SRN1 and subsequent ERC1 reactions of p-nitrobenzylidene dibromide (2b) and bromide chloride (2c) with the lithium salt (1a) and the tetrabutylammonium salt (1b) (under phase-transfer conditions) of 2-nitropropane are discussed and compared with the reactions of the dichloride (2a). The SRN1 and ERC1 sequence occurs in rapid succession in the reaction of (2b), in contrast to the reactions of (2a) and (2c) which give isolable amounts of the SRN1 product, p-NO2C6H4CH(Cl)-CMe2NO2 (3a). The monobromide p-NO2C6H4CH(Br)CMe2NO2 (3b) cannot be detected in the SRN1-ERC1 sequence leading from (2b) to β,β-dimethyl-p-nitrostyrene (5). The ERC1 reaction of the monobromide (3b) is also studied and shown to take place more slowly than the combined SRN1-ERC1 sequence for (2b). ��� The phase-transfer technique is shown to be a convenient method for the preparation of C-alkylated derivatives like (3a), but not (3b), in both-the o- and p-nitrobenzylic systems. The dibromide p- NO2C6H4CH(Br)CMe2Br (7) was shown to undergo competitive ERC1 and E2(H) reactions with (1a) to give the styrene (5) and p-NO2C6H4C(Br)=CMe2 (8) respectively. Iodide ion reacts with (7) to give the styrene (5) by an E2(Br) mechanism at a rate which is several orders of magnitude slower than the radical process. Alkoxide ions gave E2(H) reactions on dibromide (7) and monochloride (3a) with elimination of the elements of hydrogen bromide and nitrous acid respectively. The catalytic effect of white light, the inhibitive effect of oxygen and p-dinitrobenzene, and the effect of concentration on the radical processes are discussed.

Effect of Oxygen Absorbers in Rubber

1936 ◽  
Vol 9 (2) ◽  
pp. 322-338
Author(s):  
A. A. Somerville
Keyword(s):  
Atmospheric Oxygen ◽  
Practical Experience ◽  
Working Hypothesis ◽  
Retarding Effect ◽  
Full Effect ◽  
Rubber Surface ◽  
Effect Of Oxygen ◽  
Cracking Tendency ◽  
Main Factor ◽  
Mechanism Of The Reaction

Abstract In this discussion of flex-cracking, its causes, and a means of controlling it, the theory that oxidation of the rubber is the main factor involved has been used as a foundation. No attempt has been made to prove chemically that oxidation of the rubber actually takes place. This would be difficult, since flex-cracked rubber does not necessarily show the ordinary signs of deterioration, but the work of Neal and Northam (4) has indicated that oxygen plays a part. The facts that oxygen absorbers definitely retard flex-cracking and also that the more strongly they are able to absorb oxygen, the greater is their retarding effect, would be difficult to explain on any other basis. The mechanism of the reaction, however, is obscure and is further complicated by the fact that the oxygen absorbers develop their full effect only in the presence of a catalytic antioxidant. As a working hypothesis it may be assumed that the oxygen absorber removes dissolved or absorbed oxygen within the rubber before and during vulcanization, while the antioxidant protects the rubber surface against atmospheric oxygen during service. It is realized that this hypothesis does not explain every fact connected with the use of oxygen absorbers to complete satisfaction and will doubtless be subject to change or modification as practical experience with these agents accumulates. In the meantime it is believed that a practical commercial means of greatly retarding the flex-cracking tendency of rubber goods has been developed.

A TEM study of the effect of oxygen on nanocavity formation and precipitation in rapid - solidified Fe-16Ni-9Cr stainless steels

1994 ◽  
Vol 52 ◽  
pp. 700-701
Author(s):  
S. Wisutmethangoon ◽  
T. F. Kelly ◽  
J.E. Flinn
Keyword(s):  
Stainless Steels ◽  
High Mobility ◽  
Hot Extrusion ◽  
Extrusion Ratio ◽  
Gas Atomization ◽  
Cavity Formation ◽  
Nucleation Sites ◽  
Heat Treated ◽  
Different Types ◽  
Effect Of Oxygen

Vacancies are introduced into the crystal phase during quenching of rapid solidified materials. Cavity formation occurs because of the coalescence of the vacancies into a cluster. However, because of the high mobility of vacancies at high temperature, most of them will diffuse back into the liquid phase, and some will be lost to defects such as dislocations. Oxygen is known to stabilize cavities by decreasing the surface energy through a chemisorption process. These stabilized cavities, furthermore, act as effective nucleation sites for precipitates to form during aging. Four different types of powders with different oxygen contents were prepared by gas atomization processing. The atomized powders were then consolidated by hot extrusion at 900 °C with an extrusion ratio 10,5:1. After consolidation, specimens were heat treated at 1000 °C for 1 hr followed by water quenching. Finally, the specimens were aged at 600 °C for about 800 hrs. TEM samples were prepared from the gripends of tensile specimens of both unaged and aged alloys.

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 689-694
Author(s):  
QINGZHI MA ◽  
QI WANG ◽  
CHU WANG ◽  
NIANJIE FENG ◽  
HUAMIN ZHAI
Keyword(s):  
Intrinsic Viscosity ◽  
Chlorine Dioxide ◽  
High Purity ◽  
Kraft Pulp ◽  
Alkaline Media ◽  
Industrial Scale ◽  
Elemental Chlorine ◽  
Effect Of Oxygen ◽  
Alkaline Tolerant ◽  
Ecf Bleaching

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

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