HALOGEN SENSITIZED PHOTOREACTIONS

1948 ◽  
Vol 26b (9) ◽  
pp. 629-642
Author(s):  
J. W. T. Spinks
Keyword(s):  
Experimental Evidence ◽  
Wave Length ◽  
Intermediate Compound ◽  
Oxidation Reactions ◽  
Chain Reaction ◽  
Chlorine Atoms ◽  
Spectroscopic Evidence ◽  
Chemical Mechanisms ◽  
Halogen Atoms ◽  
A Chain

Spectroscopic evidence indicates that reactions photosensitized by fluorine would take place by way of fluorine atoms. Similarly, the sensitizing action of chlorine will practically always be due to chlorine atoms. For bromine, when the wave length is less than 5107 Å, reaction will be by way of bromine atoms. Experiments using wave lengths 5107–6290 Å also probably involve bromine atoms although the possibility of reaction due to excited bromine molecules cannot be wholly ruled out. Iodine atoms are produced in photosensitization experiments involving iodine and wave lengths less than 4989 Å. Experimental evidence also favors the production of iodine atoms using wave lengths up to 6200 Å. Mechanisms in accordance with the above are advanced for a number of chlorine sensitized oxidation reactions. In the oxidation reactions an intermediate compound with a trivalent carbon is formed which reacts with oxygen forming a peroxide, giving rise to a chain reaction. Reactions sensitized by bromine and iodine are also discussed. It appears that all the halogen sensitized gaseous photoreactions thus far known can be explained by chemical mechanisms involving halogen atoms.

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.

Observations on a Relationship between Steroid Metabolism and the Concentration of Plasma Fibrinogen

1963 ◽  
Vol 10 (02) ◽  
pp. 400-405 ◽  
Author(s):  
B. A Amundson ◽  
L. O Pilgeram
Keyword(s):  
Blood Coagulation ◽  
Methyl Ether ◽  
Broad Spectrum ◽  
Human Subjects ◽  
Plasma Fibrinogen ◽  
Steroid Metabolism ◽  
Specific Site ◽  
Chain Reaction ◽  
Normal Human ◽  
A Chain

SummaryEnovid (5 mg norethynodrel and 0.075 mg ethynylestradiol-3-methyl ether) therapy in young normal human subjects causes an increase in plasma fibrinogen of 32.4% (P >C 0.001). Consideration of this effect together with other effects of Enovid on the activity of specific blood coagulatory factors suggests that the steroids are exerting their effect at a specific site of the blood coagulation and/or fibrinolytic system. The broad spectrum of changes which are induced by the steroids may be attributed to a combination of a chain reaction and feed-back control.

scholarly journals Pathogenesis and Management of COVID-19

2021 ◽  
Vol 11 (2) ◽  
pp. 77-93
Author(s):  
Khalid O. Alfarouk ◽  
Sari T. S. AlHoufie ◽  
Samrein B. M. Ahmed ◽  
Mona Shabana ◽  
Ahmed Ahmed ◽  
...  
Keyword(s):  
Multiple Organ Failure ◽  
Human Body ◽  
Inflammatory Mediators ◽  
Expression Patterns ◽  
Multiple Organ ◽  
Cytokine Storm ◽  
Chain Reaction ◽  
Road Map ◽  
A Chain ◽  
Global War

COVID-19, occurring due to SARS-COV-2 infection, is the most recent pandemic disease that has led to three million deaths at the time of writing. A great deal of effort has been directed towards altering the virus trajectory and/or managing the interactions of the virus with its subsequent targets in the human body; these interactions can lead to a chain reaction-like state manifested by a cytokine storm and progress to multiple organ failure. During cytokine storms the ratio of pro-inflammatory to anti-inflammatory mediators is generally increased, which contributes to the instigation of hyper-inflammation and confers advantages to the virus. Because cytokine expression patterns fluctuate from one person to another and even within the same person from one time to another, we suggest a road map of COVID-19 management using an individual approach instead of focusing on the blockbuster process (one treatment for most people, if not all). Here, we highlight the biology of the virus, study the interaction between the virus and humans, and present potential pharmacological and non-pharmacological modulators that might contribute to the global war against SARS-COV-2. We suggest an algorithmic roadmap to manage COVID-19.

Influence of initiation mode on stability and control of a chain reaction

1980 ◽  
Vol 20 (18) ◽  
pp. 1197-1204 ◽  
Author(s):  
H. T. Chen ◽  
P. A. Chartier ◽  
S. Setthachayanon
Keyword(s):  
Chain Reaction ◽  
Stability And Control ◽  
A Chain ◽  
And Control

Oxidation of Olefins Representing Some Structural Units of GR-S

1952 ◽  
Vol 25 (1) ◽  
pp. 21-32 ◽  
Author(s):  
W. C. Warner ◽  
J. Reid Shelton
Keyword(s):  
Phenyl Group ◽  
Kinetic Mechanism ◽  
Oxidation Reactions ◽  
Chain Reaction ◽  
Instantaneous Rate ◽  
Initial Oxygen ◽  
Oxidation Of Olefins ◽  
A Minor ◽  
The Relationship ◽  
Kinetics Of

Abstract Three olefins were oxidized in the liquid phase with molecular oxygen to determine the kinetics of the oxidation reactions and the relationship to oxidation of rubber. The instantaneous rate of oxidation was found to be related to the analytically determined olefin and peroxide concentrations by the equation : Rate=k (unreacted olefin)(peroxide), where rate equals moles of oxygen per mole of original olefin per hour and the parentheses represent molarities. Presence of a phenyl group was found to affect k, but only in a minor way, indicating that the same fundamental kinetic mechanism applies in both aromatic and aliphatic olefins. The data are consistent with the general kinetic mechanism of Bolland involving oxygen attack at the alpha-methylenic group. However, it appears probable that initial oxygen attack can also occur at the double bond, resulting in the formation of a peroxide biradical, which may then react with other olefin molecules, initiating the usual chain reaction mechanism.

scholarly journals On the explosion of chain-thermal reactions

1982 ◽  
Vol 24 (2) ◽  
pp. 194-202 ◽  
Author(s):  
R. O. Ayeni
Keyword(s):  
Activation Energy ◽  
Asymptotic Analysis ◽  
Upper Bound ◽  
Homogeneous Model ◽  
Chain Reaction ◽  
Isothermal Reaction ◽  
Thermal Reactions ◽  
Spatially Homogeneous ◽  
Branched Chain ◽  
A Chain

AbstractA chain reaction of oxygen (reactant) and hydrogen (active intermediary) with mtrosyl chloride (sensitizer) as a catalyst may be modelled mathematically as a non-isothermal reaction. In this paper we present an asymptotic analysis of a spatially homogeneous model of a non-isothermal branched-chain reaction. Of particular interest is the so-called explosion time and we provide an upper bound for it as a function of the activation energy which can vary over all positive values. We also establish a bound on the temperature when the activation energy is finite.

scholarly journals Synthesis of polylactic acid-diol (PLA-diol) from lactic acid and 1,4-butanediol

2016 ◽  
Vol 19 (4) ◽  
pp. 58-65
Author(s):  
Ha Thi Thai La
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Polyethylene Glycol ◽  
1H Nmr ◽  
Biodegradable Polymer ◽  
Average Molecular Weight ◽  
Chain Extension ◽  
Structure And Properties ◽  
Chain Reaction ◽  
A Chain

In this research, the PLA-diol were synthesized from lactic acid (LA) and 1.4 butanediols (BD) with a tin octoate Sn(Oct)2 catalyst at a temperature of 180 °C and the pressure 5 mmHg. The structure and properties of PLA-diol are analyzed by the following methods: GPC, 1H-NMR and DSC. As a result, with the change in the content of Sn (Oct)2 from 0.1 to 1.0%, the molecular weight Mn of PLA - diol increased gradually from 4.119,2 to 7.359,6 g / mol . In addition, the BD content increased from 2.0% to 5.0%, the average molecular weight of the product decreased gradually from 7.536,9 g / mol to 4.735 g / mol, respectively. This change will affect the ability to use PLA-diol in the next denaturation research to apply in the field of biodegradable polymer such as copolymer with polyurethane, copolymer with polyethylene glycol diacid, or chain extension with other polymer in a chain reaction,...

scholarly journals A Solution to Hunger and Food Wastage Using a Technology-Facilitated Social Supply Chain

2021 ◽  
Author(s):  
Ria Mirchandani ◽  
Keyword(s):  
Global Warming ◽  
Supply Chain ◽  
John Donne ◽  
Chain Reaction ◽  
English Poet ◽  
Food Education ◽  
A Chain ◽  
Food Wastage

In 1624, the English poet John Donne poignantly wrote, “No man is an island, entire of itself; everyman is a piece of the continent, a part of the main; … And therefore never send to know for whom the bell tolls; It tolls for thee (Donne, 1624).” Humans are intricately connected. Our actions impact each other in a chain reaction that can span geography and time, as evident from pandemics and global warming as well as the disparate distribution of food, education, wealth, and other resources. Donne’s words serve to remind us that we cannot be immune to the suffering of others caused by this disparity of resources.

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