Free radicals formed by reaction of germane with hydrogen atoms in xenon matrix at very low temperatures

1987 ◽  
Vol 86 (9) ◽  
pp. 4949-4951 ◽  
Author(s):  
K. Nakamura ◽  
N. Masaki ◽  
M. Okamoto ◽  
S. Sato ◽  
K. Shimokoshi
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Hydrogen Atoms

Free radicals formed by reaction of silane with hydrogen atoms in rare gas matrices at very low temperatures

1985 ◽  
Vol 83 (9) ◽  
pp. 4504-4510 ◽  
Author(s):  
K. Nakamura ◽  
N. Masaki ◽  
S. Sato ◽  
K. Shimokoshi
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Rare Gas ◽  
Hydrogen Atoms

E.s.r. studies on free radicals generated in poly[p-(2-hydroxyethoxy) benzoic acid] fibres at low temperatures

Polymer ◽  
1981 ◽  
Vol 22 (9) ◽  
pp. 1267-1271 ◽  
Author(s):  
Toshihiko Nagamura ◽  
Kenneth Lawrence DeVries
Keyword(s):  
Free Radicals ◽  
Benzoic Acid ◽  
Low Temperatures

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).

Studies on the thermal coking of bitumen. I. The use of pyrene-d10 as a probe for evaluating the extent of hydrogen shuttling reaction

1991 ◽  
Vol 69 (1) ◽  
pp. 116-120 ◽  
Author(s):  
M. J. Kirk ◽  
T. S. Sorensen
Keyword(s):  
Free Radicals ◽  
Key Words ◽  
Hydrogen Exchange ◽  
Solvent Free ◽  
Hydrogen Donor ◽  
Organic Reactions ◽  
Hydrogen Atoms ◽  
Donor Solvent ◽  
Key Words Bitumen

The organic reactions that take place during the thermal coking of bitumen are extremely complex and deep-seated, but obviously hydrogen atoms originally attached to carbons that form coke will have moved to a new carbon site (net addition of hydrogen, resulting in upgraded bitumen). Accompanying this process, one expects some general hydrogen shuttling between non-coking molecules. This paper describes an approach to determing the extent of this latter process by the addition of a small amount of perdeuterated pyrene to the bitumen prior to the coking operation. The in situ pyrene functions as in indicator, allowing one to establish the extent and other mechanistic details of the "hydrogen donor" reactions that take place during coking. There is no indication that the pyrene substantially modifies the normal course of the reaction, hence the analogy to an indicator. Key words: bitumen coking, pyrene, hydrogen exchange, donor solvent, free radicals.

scholarly journals Pharmacological Effects of Salvianolic Acid B Against Oxidative Damage

2020 ◽  
Vol 11 ◽  
Author(s):  
Zhun Xiao ◽  
Wei Liu ◽  
Yong-ping Mu ◽  
Hua Zhang ◽  
Xiao-ning Wang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Free Radicals ◽  
Clinical Application ◽  
Oxygen Free Radicals ◽  
Salvianolic Acid B ◽  
Related Factor ◽  
Pharmacological Effects ◽  
Hydrogen Atoms ◽  
Salvianolic Acid

Salvianolic acid B (Sal B) is one of the main active ingredients of Salvia miltiorrhiza, with strong antioxidant effects. Recent findings have shown that Sal B has anti-inflammatory, anti-apoptotic, anti-fibrotic effects and can promote stem cell proliferation and differentiation, and has a beneficial effect on cardiovascular and cerebrovascular diseases, aging, and liver fibrosis. Reactive oxygen species (ROS) include oxygen free radicals and oxygen-containing non-free radicals. ROS can regulate cell proliferation, survival, death and differentiation to regulate inflammation, and immunity, while Sal B can scavenge oxygen free radicals by providing hydrogen atoms and reduce the production of oxygen free radicals and oxygen-containing non-radicals by regulating the expression of antioxidant enzymes. The many pharmacological effects of Sal B may be closely related to its elimination and inhibition of ROS generation, and Nuclear factor E2-related factor 2/Kelch-like ECH-related protein 1 may be the core link in its regulation of the expression of antioxidant enzyme to exert its antioxidant effect. What is confusing and interesting is that Sal B exhibits the opposite mechanisms in tumors. To clarify the specific target of Sal B and the correlation between its regulation of oxidative stress and energy metabolism homeostasis will help to further understand its role in different pathological conditions, and provide a scientific basis for its further clinical application and new drug development. Although Sal B has broad prospects in clinical application due to its extensive pharmacological effects, the low bioavailability is a serious obstacle to further improving its efficacy in vivo and promoting clinical application. Therefore, how to improve the availability of Sal B in vivo requires the joint efforts of many interdisciplinary subjects.

THE REACTION OF HYDROGEN AND DEUTERIUM ATOMS WITH PROPANE

1939 ◽  
Vol 17b (12) ◽  
pp. 371-384 ◽  
Author(s):  
E. W. R. Steacie ◽  
N. A. D. Parlee
Keyword(s):  
Activation Energy ◽  
High Temperatures ◽  
Low Temperatures ◽  
Hydrogen Atoms ◽  
Temperature Range ◽  
Secondary Reactions

The reaction of hydrogen atoms with propane has been investigated over the temperature range 30° to 250 °C. by the Wood-Bonhoeffer method. The products are solely methane at low temperatures, and methane, ethane, and ethylene at higher temperatures.It is concluded that the results can be explained only by the assumption that the reaction[Formula: see text]is of importance. The bearing of this on the Rice-Herzfeld mechanisms is discussed. The activation energy of the reaction is 10 ± 2 Kcal.The main steps in the postulated mechanism are:Primary Reaction[Formula: see text]Secondary Reactions at Low Temperatures[Formula: see text]Additional Secondary Reactions at High Temperatures[Formula: see text]The reaction of deuterium atoms with propane was also investigated. It was found that the methane and ethane produced were highly deuterized, while the propane was not appreciably exchanged.

Reaction pathways of hydroxyl groups during coal spontaneous combustion

2016 ◽  
Vol 94 (5) ◽  
pp. 494-500 ◽  
Author(s):  
Xuyao Qi ◽  
Haibo Xue ◽  
Haihui Xin ◽  
Cunxiang Wei
Keyword(s):  
Activation Energy ◽  
Free Radicals ◽  
Hydrogen Abstraction ◽  
Enthalpy Change ◽  
Reaction Pathways ◽  
Hydroxyl Groups ◽  
Hydrogen Atoms ◽  
Typical Structure ◽  
Self Heating ◽  
Hydroxyl Free Radicals

Hydroxyl groups are one of the key factors for the development of coal self-heating, although their detailed reaction pathways are still unclear. This study investigated the reaction pathways in coal self-heating by the method of quantum chemistry calculation. The Ar–CH2–CH(CH3)–OH was selected as a typical structure unit for the calculation. The results indicate that the hydrogen atoms in hydroxyl groups and R3–CH are the active sites. For the hydrogen atoms in hydroxyl groups, they are directly abstracted by oxygen. For hydrogen atoms in R3–CH, they are abstracted by oxygen at first and generate peroxy-hydroxyl free radicals, which abstract the hydrogen atoms in hydroxyl groups later. The reaction of R3–CH contains three elementary reactions, i.e., the hydrogen abstraction of R3–CH by oxygen, the conjugation reaction between the R3C■ and oxygen atom, and the hydrogen abstraction of –OH by hydroxyl free radicals. Then, the microstructure parameters, IRC pathways, and reaction dynamic parameters were respectively analyzed for the four reactions. For the hydrogen abstraction of –OH by oxygen, the enthalpy change and activation energy are 137.63 and 334.44 kJ/mol, respectively, which will occur at medium temperatures and the corresponding heat effect is great. For the reaction of R3–CH, the enthalpy change and the activation energy are −3.45 and 55.79 kJ/mol, respectively, which will occur at low temperatures while the corresponding heat influence is weak. They both affect heat accumulation and provide new active centers for enhancing the coal self-heating process. The results would be helpful for further understanding of the coal self-heating mechanism.

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