THE REACTIONS OF METHYL AND ETHYL RADICALS WITH DIETHYL KETONE

1954 ◽  
Vol 32 (6) ◽  
pp. 593-597 ◽  
Author(s):  
P. Ausloos ◽  
E. W. R. Steacie
Keyword(s):  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Diethyl Ketone ◽  
Temperature Range ◽  
Steric Factors ◽  
Ethyl Radicals

The hydrogen-abstraction reactions of methyl and ethyl radicals from diethyl ketone have been studied in the temperature range 25 to 160 °C. Azomethane and azoethane were used as photochemical sources of methyl and ethyl radicals. The activation energies found were 7.0 and 7.6 kcal., respectively, for the reactions:[Formula: see text][Formula: see text]If the combination of both methyl and ethyl radicals is assumed to occur at every collision, the steric factors for the two reactions are E1 = 7.4 × 10−4, E2 = 7.1 × 10−4.

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.

Reactions of trifluoromethyl radicals. V. Hydrogen abstraction from methyl acetate and methyl (2H3)Acetate

1980 ◽  
Vol 33 (7) ◽  
pp. 1437
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Methoxy Group ◽  
Methyl Acetate ◽  
Kinetic Isotope Effect ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Temperature Range ◽  
Kinetic Isotope ◽  
Acetyl Group

Hydrogen abstraction by CF3 radicals from CH3COOCH3 and CD3COOCH3 has been studied in the temperature range 78-242°, and data have been obtained for the reactions: CF3 + CH3COOCH3 → CF3H+[C3H5O2] �������������(3) CF3 + CH3COOCH3 → CF3H+CH2COOCH3������������ (4) CF3 + CD3COOCH3 → CF3D+CD2COOCH3������������ (6) CF3 + CD3COOCH3 → CF3H+CD3COOCH2������������ (7) The corresponding rate constants, based on the value of 1013.36 cm3 mol-1 S-1 for the recombination of CF3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk3 = (11.52�0.05)-(35430�380)/19.145T ���� (3)logk4 = (11.19�0.07)-(34680�550)/19.145T ���� (4)logk6 = (11.34�0.06)-(46490�490)/19.145T ���� (6)logk7 = (11.26�0.05)-(36440�400)/19.145T ���� (7)At 400 K, 59% of abstraction occurs from the acetyl group, and 41 % from the methoxy group. The kinetic isotope effect at 400 K for attack on the acetyl group is 25, due mainly to a difference in activation energies.

Reactions of trifluoromethyl radicals. II. Hydrogen abstraction from monochlorosilane

1973 ◽  
Vol 26 (6) ◽  
pp. 1269 ◽  
Author(s):  
NL Arthur ◽  
BR Harman
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Experimental Error ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Hydrogen Atom Abstraction ◽  
Temperature Range ◽  
Average Value

Hydrogen atom abstraction from SiH3Cl by CF3 radicals ����������������� CF3 + SiH3Cl → CF3H+SiH2Cl������������������� (1) has been studied in the temperature range 69-168�. The rate constant, based on Ayscough's value of 1013.36 cm3 mol-1 s-1 for the recombination of CF3 radicals, is given by (k1 in cm3 mol-1 s-1, E in kJ mol-1): ������������������ logk1 = (12.38�0.06)-(25.72�0.41)/2.303RT At 400 K, the rate constant for CF3 + SiH3Cl is greater than the average value reported for CF3+SiHCl3 by a factor of 3.6. This is due to a difference in A factors since the activation energies are equal within experimental error.

Reactions of Methyl Radicals. II. Hydrogen Abstraction from Methyl Trifluoroacetate

1979 ◽  
Vol 32 (5) ◽  
pp. 1025 ◽  
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Methyl Radicals ◽  
Temperature Range ◽  
Cf3 Radical

Hydrogen abstraction from CF3COOCH3 and CH3COCH3 by CH3 radicals CF3 + CF3COOCH3 → CH4 + CF3COOCH2 (1) CF3 + CF3COOCH3 → CH4 + CH3COCH2 (3) has been studied in the temperature range 117-244�. The rate constants, based on the value of 1013.34 cm3 mol-1 s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1) : logk1 = (10.39 � 0.11)- (37680 � 880)/19.145T logk3 = (11.53 � 0.02)- (40590 � 170)/19.145T CF3COOCH3 is less susceptible to attack by CH3 radicals than by CF3 radicals by a factor of 2.8 at 400 K, due mainly to a difference in A factors, since the activation energies of the two reactions are almost identical. These results can be rationalized in terms of intermolecular polar repulsion between the CF3 radical and CF3COOCH3.

PHOTOLYSIS OF 2, 2′, 4, 4′-TETRADEUTERODIETHYL KETONE

1951 ◽  
Vol 29 (12) ◽  
pp. 1092-1103 ◽  
Author(s):  
M. H. J. Wijnen ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Diethyl Ketone ◽  
Temperature Range ◽  
A Value ◽  
Ethyl Radicals

The photolysis of CH3CD2COCD2CH3 has been studied over a temperature range from 25°C. to 365°C. The results confirm several features of the mechanism, previously proposed for the photolysis of diethyl ketone. It is concluded that disproportionation of ethyl radicals occurs by a "head to tail" mechanism. As activation energy for the reaction[Formula: see text]a value E4 = 8.7 kcal. was found. As activation energy for Reaction (5)[Formula: see text]a value of E5 = 11.7 kcal. was found. An activation energy of ∼ 17 kcal. is estimated for the thermal decomposition of the pentanonyl radical

Rate constants for abstraction of hydrogen from benzene, toluene, and cyclopentane by methyl and ethyl radicals over the temperature range 650–770 K

1989 ◽  
Vol 67 (10) ◽  
pp. 1541-1549 ◽  
Author(s):  
H.-X. Zhang ◽  
S. I. Ahonkhai ◽  
M. H. Back
Keyword(s):  
Rate Constants ◽  
Activation Energies ◽  
Ethyl Benzene ◽  
Methyl Ethyl ◽  
Chain Reactions ◽  
Temperature Range ◽  
Dissociation Energies ◽  
Abstraction Reaction ◽  
Benzene Toluene ◽  
Ethyl Radicals

Rate constants for the abstraction of hydrogen from benzene, toluene, and cyclopentane by methyl and ethyl radicals have been measured relative to the corresponding abstraction reaction from ethylene. The method is based on the effect on the rates of formation of methane and ethane of the addition of small quantities of the reactants to the thermal chain reactions of ethylene in the temperature range 650–770 K. Taking the following values of the rate constants for the reference reactions (R = 8.314 J mol−1 K−1):[Formula: see text]the following rate constants were measured:[Formula: see text]The values of the activation energies are discussed in relation to the dissociation energies of the C—H bonds in the reactants. Keywords: kinetics, abstraction, methyl, ethyl, benzene, toluene.

scholarly journals High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 581
Author(s):  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Threshold Stress ◽  
Activation Energies ◽  
Temperature Deformation ◽  
High Temperature Range ◽  
Temperature Range ◽  
True Activation Energy ◽  
Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

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.

MECHANISM AND KINETICS OF THE CH3CH2C(O)OCH2CH3 + OH REACTION: A THEORETICAL STUDY

2011 ◽  
Vol 10 (05) ◽  
pp. 691-709 ◽  
Author(s):  
CONG HOU ◽  
CHENG-GANG CI ◽  
TONG-YIN JIN ◽  
YONG-XIA WANG ◽  
JING-YAO LIUM
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Negative Temperature ◽  
State Theory ◽  
Measured Temperature ◽  
Temperature Range ◽  
Global Rate ◽  
Abstraction Reaction ◽  
Lower Temperature ◽  
Kinetic Calculations

The hydrogen abstraction reaction of CH 3 CH 2 C(O)OCH 2 CH 3 + OH has been studied theoretically by dual-level direct dynamics method. Six H-abstraction channels were found for this reaction. The required potential energy surface information for the kinetic calculations was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants were calculated by the improved canonical variational transition-state theory with small-curvature tunneling correction (ICVT/SCT) approach in the temperature range of 200–2000 K. It is shown that the "methylene H-abstraction" from the alkoxy end of the ester CH 3 CH 2 C(O)OCH 2 CH 3 is the dominant channel at lower temperature (< 400 K), while the other channels from the acetyl end should be taken into account as the temperature increases and become the competitive ones at higher temperature. The calculated global rate constants are in good agreement with the experimental ones in the measured temperature range and exhibit a negative temperature dependence below 500 K. A four-parameter rate constant expression was fitted from the calculated kinetic data between 200–2000 K.

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