scholarly journals The Kinetics of Joined Action of Triplet-Triplet Annihilation and First-Order Decay of Molecules in the State in the Case of Nondominant First-Order Process

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Paweł Borowicz ◽  
Bernhard Nickel
Keyword(s):  
Delayed Fluorescence ◽  
Second Order ◽  
Rate Parameter ◽  
Second Order Reaction ◽  
Order Process ◽  
First Order ◽  
Diffusion Controlled ◽  
Proposed Model ◽  
Kinetics Of ◽  
Triplet Triplet Annihilation

This paper presents the description of triplet-triplet annihilation in the case of nondominant first-order decay of molecules in the triplet state. The kinetics of the statistical system is influenced by joined action of two processes: the first- and second-order decies. This kinetics can be described with analytical function if the rate parameter of second-order reaction is constant. The approach presented here combines the well-known Smoluchowski formula with the previously published intuitive and non-Fickian models of diffusion-controlled triplet-triplet annihilation. The kinetics of the delayed fluorescence of anthracene is used as a practical example of applicability of the model proposed. The advantages and limits of the proposed model are discussed.

scholarly journals The Kinetics of Joined Action of Triplet-Triplet Annihilation and First-Order Decay of Molecules in T1State in the Case of Nondominant First-Order Process: The Kinetic Model in the Case of Spatially Periodic Excitation

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Paweł Borowicz ◽  
Bernhard Nickel
Keyword(s):  
Diffusion Coefficient ◽  
Kinetic Model ◽  
Periodic Pattern ◽  
Constructive Interference ◽  
First Order ◽  
Dependent Rate ◽  
Diffusion Controlled ◽  
Spatially Periodic ◽  
Kinetics Of ◽  
Triplet Triplet Annihilation

In this paper the model developed for estimation of the diffusion coefficient of the molecules in the triplet state is presented. The model is based on the intuitive modification of the Smoluchowski equation for the time-dependent rate parameter. Since the sample is irradiated with the spatially periodic pattern nonexponential effects can be expected in the areas of the constructive interference of the exciting laser beams. This nonexponential effects introduce changes in the observed kinetics of the diffusion-controlled triplet-triplet annihilation. Due to irradiation with so-called long excitation pulse these non-exponential effects are very weak, so they can be described with introducing very simple correction to the kinetic model described in the first paper of this series. The values of diffusion coefficient of anthracene are used to calculate the annihilation radius from the data for spatially homogeneous excitation.

KINETICS OF THE PHOTOCHLORINATION OF MONOCHLOROMETHYL CHLOROFORMATE IN THE GAS PHASE

1957 ◽  
Vol 35 (11) ◽  
pp. 1341-1350 ◽  
Author(s):  
M. J. Dignam ◽  
W. G. Forbes ◽  
D. J. Le Roy
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Hydrogen Abstraction ◽  
The Other ◽  
Third Body ◽  
Order Process ◽  
First Order ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
Atomic Chlorine

The general features of the mechanism of the over-all process [Formula: see text][Formula: see text] are similar to those for the over-all process [Formula: see text][Formula: see text] studied previously. The reaction is inhibited by HCl. Chains are terminated by two processes, one of which is first order, the other second order in atomic chlorine. The first order process is not entirely diffusion controlled and a theory is advanced to account for its nature; the homogeneous combination of chlorine atoms requires a third body, mono- and di-chloromethyl chloroformate being particularly effective. The activation energy for hydrogen abstraction from monochloromethyl chloroformate by atomic chlorine is 5.2 kcal. per mole. The C—H bond dissociation energy in monochloromethyl chloroformate is estimated to be 99.8 ± 4.5 kcal. per mole.

Kinetics of the reaction between hexamethylenediisocyanate and 1-pentanol

1983 ◽  
Vol 48 (11) ◽  
pp. 3279-3286
Author(s):  
Slavko Hudeček ◽  
Miloslav Bohdanecký ◽  
Ivana Hudečková ◽  
Pavel Špaček ◽  
Pavel Čefelín
Keyword(s):  
Liquid Chromatography ◽  
Rate Constants ◽  
Reversed Phase ◽  
Order Reaction ◽  
Second Order ◽  
Second Order Reaction ◽  
Reversed Phase Liquid Chromatography ◽  
Consecutive Reactions ◽  
Phase Liquid ◽  
Kinetics Of

The reaction between hexamethylenediisocyanate and 1-pentanol in toluene was studied by means of reversed-phase liquid chromatography. By employing this method, it was possible to determine all components of the reaction mixture including both products, i.e. N-(6-isocyanate hexyl)pentylcarbamate and N,N'-bis(pentyloxycarbonyl)hexamethylenediamine. Relations for the calculation of kinetic constants were derived assuming a competitive consecutive second-order reaction. It was demonstrated that the reaction involved in this case is indeed a second-order reaction, and the rate constants of the first and second consecutive reactions were determined.

Evidence for general base catalysis by protic solvents in a kinetic study of alcoholyses and hydrolyses of 1-(phenoxycarbonyl)pyridinium ions under both solvolytic and non-solvolytic conditions

2009 ◽  
Vol 74 (1) ◽  
pp. 43-55 ◽  
Author(s):  
Dennis N. Kevill ◽  
Byoung-Chun Park ◽  
Jin Burm Kyong
Keyword(s):  
Second Order ◽  
Base Catalysis ◽  
Substitution Reactions ◽  
Third Order ◽  
Methoxy Derivative ◽  
First Order ◽  
General Base ◽  
Protic Solvents ◽  
Kinetics Of ◽  
Pyridinium Ions

The kinetics of nucleophilic substitution reactions of 1-(phenoxycarbonyl)pyridinium ions, prepared with the essentially non-nucleophilic/non-basic fluoroborate as the counterion, have been studied using up to 1.60 M methanol in acetonitrile as solvent and under solvolytic conditions in 2,2,2-trifluoroethan-1-ol (TFE) and its mixtures with water. Under the non- solvolytic conditions, the parent and three pyridine-ring-substituted derivatives were studied. Both second-order (first-order in methanol) and third-order (second-order in methanol) kinetic contributions were observed. In the solvolysis studies, since solvent ionizing power values were almost constant over the range of aqueous TFE studied, a Grunwald–Winstein equation treatment of the specific rates of solvolysis for the parent and the 4-methoxy derivative could be carried out in terms of variations in solvent nucleophilicity, and an appreciable sensitivity to changes in solvent nucleophilicity was found.

scholarly journals REGENERATION OF VISUAL PURPLE IN SOLUTION

1939 ◽  
Vol 23 (1) ◽  
pp. 21-39 ◽  
Author(s):  
Aurin M. Chase ◽  
Emil L. Smith
Keyword(s):  
Order Process ◽  
First Order ◽  
Color Changes ◽  
Violet Light ◽  
Frog Retina ◽  
Significant Difference ◽  
Kinetics Of ◽  
Photosensitive Substance ◽  
Subsequent Regeneration

1. Measurements of visual purple regeneration in solution have been made by a procedure which minimized distortion of the results by other color changes so that density changes caused by the regenerating substance alone are obtained. 2. Bleaching a visual purple solution with blue and violet light causes a greater subsequent regeneration than does an equivalent bleaching with light which lacks blue and violet. This is due to a photosensitive substance which has a gradually increasing effective absorption toward the shorter wavelengths. It is uncertain whether this substance is a product of visual purple bleaching or is present in the solution before illumination. 3. The regeneration of visual purple measured at 560 mµ is maximal at about pH 6.7 and decreases markedly at more acid and more alkaline pH's. 4. The absorption spectrum of the regenerating material shows only a concentration change during the course of regeneration, but has a higher absorption at the shorter wavelengths than has visual purple before illumination. 5. Visual purple extractions made at various temperatures show no significant difference in per cent of regeneration. 6. The kinetics of regeneration is usually that of a first order process. Successive regenerations in the same solution have the same velocity constant but form smaller total amounts of regenerated substance. 7. In vivo, the frog retina shows no additional oxygen consumption while visual purple is regenerating.

Spectrochemical Behavior of Carcinogenic Polycyclic Aromatic Hydrocarbons in Biological Systems. Part II: A Theoretical Rate Model for BaP Metabolism in Living Cells

1996 ◽  
Vol 50 (11) ◽  
pp. 1352-1359 ◽  
Author(s):  
Ping Chiang ◽  
Kuang-Pang Li ◽  
Tong-Ming Hseu
Keyword(s):  
Rate Constant ◽  
Living Cells ◽  
Rate Model ◽  
Number Density ◽  
Order Process ◽  
Irreversible Reaction ◽  
First Order ◽  
Metabolism Rate ◽  
Polycyclic Aromatic ◽  
Kinetics Of

An idealized model for the kinetics of benzo[ a]pyrene (BaP) metabolism is established. As observed from experimental results, the BaP transfer from microcrystals to the cell membrane is definitely a first-order process. The rate constant of this process is signified as k1. We describe the surface–midplane exchange as reversible and use rate constants k2 and k3 to describe the inward and outward diffusions, respectively. The metabolism is identified as an irreversible reaction with a rate constant k4. If k2 and k3 are assumed to be fast and not rate determining, the effect of the metabolism rate, k4, on the number density of BaP in the midplane of the microsomal membrane, m3, can be estimated. If the metabolism rate is faster than or comparable to the distribution rates, k2 and k3, the BaP concentration in the membrane midplane, m3, will quickly be dissipated. But if k4 is extremely small, m3 will reach a plateau. Under conditions when k2 and k3 also play significant roles in determining the overall rate, more complicated patterns of m3 are expected.

scholarly journals Kinetics of Phenolic Compounds Modification during Maize Flour Fermentation

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6702
Author(s):  
Oluwafemi Ayodeji Adebo ◽  
Ajibola Bamikole Oyedeji ◽  
Janet Adeyinka Adebiyi ◽  
Chiemela Enyinnaya Chinma ◽  
Samson Adeoye Oyeyinka ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Phenolic Acids ◽  
Kinetic Models ◽  
Titratable Acidity ◽  
Second Order ◽  
Soluble Solids ◽  
Maize Flour ◽  
First Order ◽  
Compound Modification ◽  
Kinetics Of

This study aimed to investigate the kinetics of phenolic compound modification during the fermentation of maize flour at different times. Maize was spontaneously fermented into sourdough at varying times (24, 48, 72, 96, and 120 h) and, at each point, the pH, titratable acidity (TTA), total soluble solids (TSS), phenolic compounds (flavonoids such as apigenin, kaempferol, luteolin, quercetin, and taxifolin) and phenolic acids (caffeic, gallic, ferulic, p-coumaric, sinapic, and vanillic acids) were investigated. Three kinetic models (zero-, first-, and second-order equations) were used to determine the kinetics of phenolic modification during the fermentation. Results obtained showed that fermentation significantly reduced pH, with a corresponding increase in TTA and TSS. All the investigated flavonoids were significantly reduced after fermentation, while phenolic acids gradually increased during fermentation. Among the kinetic models adopted, first-order (R2 = 0.45–0.96) and zero-order (R2 = 0.20–0.82) equations best described the time-dependent modifications of free and bound flavonoids, respectively. On the other hand, first-order (R2 = 0.46–0.69) and second-order (R2 = 0.005–0.28) equations were best suited to explain the degradation of bound and free phenolic acids, respectively. This study shows that the modification of phenolic compounds during fermentation is compound-specific and that their rates of change may be largely dependent on their forms of existence in the fermented products.

scholarly journals The alcoholysis of 1,2,2-trimethylpropyl-methylfluorophosphonate

2000 ◽  
Vol 65 (12) ◽  
pp. 857-866
Author(s):  
Mladjen Micevic ◽  
Slobodan Petrovic
Keyword(s):  
Kinetic Data ◽  
Reaction Rate ◽  
Frequency Factor ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
Activation Entropy ◽  
Second Order Reaction ◽  
Third Order ◽  
First Order ◽  
Kinetics Of

The alcoholysis of 1,2,2-trimethylpropyl-methylfluorophosphonate (soman) was examined with a series of alkoxides and in corresponding alcohols: methanol, ethanol, 1-propanol, 2-propanol, 2-methoxyethanol and 2-ethoxyethanol. Soman reacts with the used alkoxides in a second order reaction, first order in each reactant. The kinetics of the reaction between 1,2,2-trimethylpropyl-methylfluorophosphonate and ethanol in the presence of diethylenetriamine was also examined. A third order reaction rate constant was calculated, first order in each reactant. The activation energy, frequency factor and activation entropy were determined on the basis of the kinetic data.

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