PHOTOLYSIS OF ACETONE IN THE PRESENCE OF MERCURY DIMETHYL

1955 ◽  
Vol 33 (3) ◽  
pp. 472-479 ◽  
Author(s):  
H. G. Oswin ◽  
R. Rebbert ◽  
E. W. R. Steacie
Keyword(s):  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Activation Energies ◽  
Reaction Products ◽  
Kcal Mole ◽  
Constant Intensity ◽  
Acetone Concentration ◽  
Significant Difference

The reactions between CH3 + CH3—Hg—CH3 were investigated in a system in which acetone was used as the source of CH3 radicals. Similarly d6-acetone was used to investigate the reactions of CD3 radicals and CH3—Hg—CH3. Activation energies for the hydrogen abstraction reactions were calculated, and no significant difference was found between the CD3 and CH3 reactions, being respectively 10.0 and 10.2 kcal./mole. Under conditions of constant intensity and acetone concentration, reaction rates appear to be dependent on mercury dimethyl concentrations. In the case of the acetone-d6 system, quantities of C2D3H3 were found in the reaction products. This is discussed as possible evidence of such a reaction as:[Formula: see text]

THE REACTIONS OF TRIFLUOROMETHYL RADICALS WITH PROPANE, n-BUTANE, AND ISOBUTANE

1956 ◽  
Vol 34 (2) ◽  
pp. 103-107 ◽  
Author(s):  
P. B. Ayscough ◽  
E. W. R. Steacie
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Methyl Radicals ◽  
Kcal Mole

A study of the reactions of trifluoromethyl radicals, produced by the photolysis of hexafluoroacetone, with propane, n-butane, and isobutane has been made. The rate constants of the hydrogen-abstraction reactions have been determined at temperatures between 27 °C and 119 °C and the activation energies found to be 6.5 ± 0.5, 5.1 ± 0.3, and 4.7 ± 0.3 kcal./mole respectively. These values are compared with those obtained for the reactions with methane and ethane, and with the corresponding reactions of methyl radicals.

THE REACTIONS OF PERFLUOROETHYL RADICALS WITH HYDROGEN AND METHANE

1960 ◽  
Vol 38 (11) ◽  
pp. 2128-2135 ◽  
Author(s):  
S. J. W. Price ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Hydrogen Abstraction ◽  
Frequency Factor ◽  
Activation Energies ◽  
Recombination Reaction ◽  
Limited Data ◽  
Kcal Mole ◽  
Fluorinated Radical

The reactions of C2F5 radicals, produced by the photolysis of (C2F5)2CO, with methane and hydrogen have been studied. Assuming zero activation energy for 2C2F5 → C4F10 the activation energies for C2F5 + CH4 → C2F5H + CH3 and C2F5 + H2 → C2F5H + H are 10.6 kcal/mole and 11.9 kcal/mole respectively. The present results have been correlated with data on the reactions of CF3, C3F7, and CH3 radicals with H2, D2, CH4, and C2H6. Taking Erecombination ≈ 0 in all cases and assuming the frequency factor for the recombination reaction varies little from radical to radical, the order of ease of hydrogen abstraction from a given substrate is CF3 > C2F5 > C3F7 > CH3. Similarly the ease of hydrogen abstraction from a substrate by a given fluorinated radical is C2H6 > H2 > CH4 > D2. A calculation based on very limited data indicates the reaction CH3 + C2F5COC2F5 → CH3COC2F5 + C2F5 may occur with an activation energy of approximately 7 kcal/mole.

HYDROGEN ATOM ABSTRACTION BY ETHYL-d5 RADICALS. PART I

1960 ◽  
Vol 38 (9) ◽  
pp. 1576-1589 ◽  
Author(s):  
P. J. Boddy ◽  
E. W. R. Steacie
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Abstraction ◽  
Deuterium Atom ◽  
Structural Features ◽  
Activation Energies ◽  
Hydrogen Atom Abstraction ◽  
Kcal Mole ◽  
Temperature Range ◽  
Exponential Factors ◽  
Ethyl Radicals

The photolysis of 3-pentanone-d10 has been used as a source of deuterated ethyl radicals and some of their hydrogen abstraction reactions studied over the temperature range 50–300 °C.The compounds neopentane, n-butane, and isobutane were chosen as representative of the basic structural features in the alkane series. The activation energies for abstraction [Formula: see text] are respectively 12.60 ± 0.7, 10.4 ± 0.75, and 8.9 ± 0.6 kcal/mole and the pre-exponential factors (log10(A8/A4)) are 0.300 ± 0.09, 0.082 ± 0.09, and −0.334 ± 0.066 where[Formula: see text]For abstraction of a deuterium atom from the ketone the values obtained are [Formula: see text] in agreement with previous investigations (1, 2).The value of the disproportionation to combination ratio for C2D5 radicals is 0.0985 ± 0.008 independent of temperature.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

The Reaction and Microscopic Electron Properties from Dynamic Evolutions of Condensed-Phase RDX Under Shock Loading

2020 ◽  
Vol 75 (4) ◽  
pp. 285-291
Author(s):  
Jiao-Nan Yuan ◽  
Hai-Chao Ren ◽  
Yong-Kai Wei ◽  
Wei-Sen Xu ◽  
Guang-Fu Ji ◽  
...  
Keyword(s):  
Shock Wave ◽  
Ground State ◽  
Shock Loading ◽  
Reaction Rates ◽  
Reaction Products ◽  
Decomposition Rates ◽  
Multi Scale ◽  
Wave Velocities ◽  
Wide Gap ◽  
Reaction Initiation

AbstractMicroscopic electron properties of α-hexahydro-1,3,5-trinitro-1,3,5-triazine (α-RDX) with different shock wave velocities have been investigated based on molecular dynamics together with multi-scale shock technique. The studied shock wave velocities are 8, 9 and 10 km ⋅ s−1. It has been said that the shock sensitivity and reaction initiation of explosives are closely relevant with their microscopic electron properties. The reactions, including the reaction products, which are counted from the trajectory during the simulations are analysed first. The results showed that the number of the products strictly rely on shock wave velocities. The reaction rates and decomposition rates are also studied, which showed the differences between the different shock velocities. The results of electron properties show that α-RDX is a wide-gap insulator in the ground state and the metallisation conditions of shocked RDX are determined, which are lower than under-static high pressure.

scholarly journals Effect of Nitrogen on the Growth of (100)-, (110)-, and (111)-Oriented Diamond Films

2020 ◽  
Vol 11 (1) ◽  
pp. 126
Author(s):  
Jen-Chuan Tung ◽  
Tsung-Che Li ◽  
Yen-Jui Teseng ◽  
Po-Liang Liu
Keyword(s):  
Growth Mechanism ◽  
Density Functional ◽  
Film Growth ◽  
Hydrogen Abstraction ◽  
Diamond Films ◽  
Activation Energies ◽  
Diamond Surface ◽  
Nitrogen Doped ◽  
Nitrogen Substitution ◽  
Diamond Film Growth

The aim of this research is the study of hydrogen abstraction reactions and methyl adsorption reactions on the surfaces of (100), (110), and (111) oriented nitrogen-doped diamond through first-principles density-functional calculations. The three steps of the growth mechanism for diamond thin films are hydrogen abstraction from the diamond surface, methyl adsorption on the diamond surface, and hydrogen abstraction from the methylated diamond surface. The activation energies for hydrogen abstraction from the surface of nitrogen-undoped and nitrogen-doped diamond (111) films were −0.64 and −2.95 eV, respectively. The results revealed that nitrogen substitution was beneficial for hydrogen abstraction and the subsequent adsorption of methyl molecules on the diamond (111) surface. The adsorption energy for methyl molecules on the diamond surface was generated during the growth of (100)-, (110)-, and (111)-oriented diamond films. Compared with nitrogen-doped diamond (100) films, adsorption energies for methyl molecule adsorption were by 0.14 and 0.69 eV higher for diamond (111) and (110) films, respectively. Moreover, compared with methylated diamond (100), the activation energies for hydrogen abstraction were by 0.36 and 1.25 eV higher from the surfaces of diamond (111) and (110), respectively. Growth mechanism simulations confirmed that nitrogen-doped diamond (100) films were preferred, which was in agreement with the experimental and theoretical observations of diamond film growth.

scholarly journals REACTIVITY OF NUCLEOPHILES AND α-EFFECT IN SUBSTITUTION PROCESSES AT ELECTRON - DEFICIENCY CENTERS

2020 ◽  
Vol 86 (7) ◽  
Author(s):  
Anatolii Popov ◽  
Illia Kapitanov ◽  
Anna Serdyuk ◽  
Aleksandr Sumeiko
Keyword(s):  
Organic Phosphorus ◽  
Organophosphorus Pesticides ◽  
Reaction Rates ◽  
Hydroxamic Acids ◽  
Phosphorus Compounds ◽  
Reaction Products ◽  
Electron Pairs ◽  
Alkyl Derivatives ◽  
Solvent Type ◽  
Electron Deficiency

The review analyzes issues related to the reactivity of nucleophiles and the manifestation of the α-effect in substitution processes at electron-deficient centers. The fundamental aspects of this phenomenon, as well as the possibilities and prospects of using α-nucleophiles in systems for the highly efficient degradation of substrates - ecotoxicants of various natures, are discussed. In the first part of the review such aspects were observed: inorganic α-nucleophiles as the most effective class of reagents for the decomposition of organic phosphorus compounds, hydroxylamine, its N-alkyl derivatives, oximes, and hydroxamic acids, reactivity of the НОО– anion in the processes of acyl group transfer, reactivity of oximate ions, inorganic α-nucleophiles as the basis of formulations for the degradation of neurotoxins, vesicants, and organophosphorus pesticides, design of inhibited acetylcholinesterase reactivators based on hydroxylamine derivatives, ways of structural modification of α-nucleophiles and systems based on them. The data on the reactivity of typical inorganic α-nucleophiles in the cleavage of acyl-containing substrates, including phosphorus acid esters, which provide abnormally high reaction rates in comparison with other supernucleophiles, are analyzed. Various types of such α-nucleophiles, features of their structure and reactivity are considered. It was shown that an important feature of hydroxylamine, oximes, and hydroxamic acids is the presence of a fragment with adjacent O and N (–N – O – H) atoms containing one or more lone electron pairs, which determines their belonging to the class of α-nucleophiles. It has been shown that a many of factors can be responsible for the manifestation of the α-effect and its magnitude, the main of which is the destabilization of the ground state of the nucleophile due to repulsion of lone electron pairs, stabilization of the transition state, the unusual thermodynamic stability of reaction products, solvation effects of the solvent, type of hybridization of the electrophilic center, etc.

Tracer Impurity Diffusion in Liquid Metals: K in Na and Na in K

1973 ◽  
Vol 28 (1) ◽  
pp. 117-119
Author(s):  
T. Persson ◽  
S. J. Larsson
Keyword(s):  
Liquid Metals ◽  
Activation Energies ◽  
Impurity Diffusion ◽  
Effective Activation ◽  
Kcal Mole ◽  
Self Diffusion

The diffusivities of 42K in Na and of 24Na in K have been measured between 100 ° and 285 °C, utilizing an „infinite capillary" technique. The results are adequately described by the Arrhenius relations (in cm2/s) DK in Na = 0.46 · 10-3 exp (-1.82/RT) and DNa in K = 0.93 · 10-3 exp (-2.11/RT). The differences ΔQ in effective activation energies between impurity diffusion and self-diffusion are about -0.4 kcal/mole for Na and +0.1 kcal/mole for K. This can be satisfactorily explained by electrostatic screening arguments. The impurity diffuses slower than the host atoms in Na, faster in K.

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