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 trifluoromethyl radicals. I. Hydrogen abstraction from dimethyl sulphide

1972 ◽  
Vol 25 (4) ◽  
pp. 803 ◽  
Author(s):  
NL Arthur ◽  
KS Yeo
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Hydrogen Atom Abstraction ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen atom abstraction from (CH3)2S by CF3 radicals has been studied in the temperature range 79-167�: (1) CF3 + CH3SCH3 ←→ CF3H + CH3SCH2 (-1) The rate constant, based on Ayscough's value of 1013.36cmS mol-l s-l for the recombination of CF3 radicals, is given by (k1 in cm3 mol-1 s-l, E in J mol-l): Logk1 = (12.05 � 0.02)-(28710 � 130)/2.303RT Combination of these results with thermochemical data gives a calculated value of log k-1 = 12.2 - 62600/2.303RT for the rate constant of the reverse reaction. ΔH�f(CH3SCH2) and S�(CH3SCH2) are estimated to be 155.6 kJ mol-l and 290 J K-l mol-1 respectively.

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.

Influence of the double bond on the hydrogen abstraction reactions of methyl esters with hydrogen radical: an ab initio and chemical kinetic study

RSC Advances ◽  
2015 ◽  
Vol 5 (84) ◽  
pp. 68314-68325 ◽  
Author(s):  
Quan-De Wang ◽  
Weidong Zhang
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Ab Initio ◽  
Kinetic Study ◽  
Rate Constants ◽  
Methyl Esters ◽  
Hydrogen Abstraction ◽  
Chemical Kinetic ◽  
Hydrogen Atom Abstraction ◽  
Hydrogen Radical

This work reports a systematic ab initio and chemical kinetic study of the rate constants for hydrogen atom abstraction reactions by hydrogen radical on the isomers of unsaturated C6 methyl esters.

Self-diffusion in Molten Zinc Bromide

1963 ◽  
Vol 18 (12) ◽  
pp. 1247-1248 ◽  
Author(s):  
Carl-Axel Sjöblom
Keyword(s):  
Diffusion Coefficient ◽  
Experimental Error ◽  
Activation Energies ◽  
Zinc Bromide ◽  
Molten Zinc ◽  
Temperature Range ◽  
Self Diffusion ◽  
Bromide Ion

The diffusion coefficient of the bromide ion in molten zinc bromide has been measured in the temperature range 415—547°C. The results can be described by the following equation1:D = 0.114 exp [ — (17 050 ± 500) /R T].D is expressed in cm2s-1, R in cal · mole-1 · degree-1 and T in degrees KELVIN. A comparison with earlier measurements 2 shows that the activation energies of cation and anion are equal within the experimental error, and that D- is considerably greater than D+ in the whole temperature range.

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.

Reactions of methyl radicals. V. Hydrogen abstraction from hydrogen sulfide

1983 ◽  
Vol 36 (11) ◽  
pp. 2195 ◽  
Author(s):  
H Arican ◽  
NL Arthur
Keyword(s):  
Hydrogen Sulfide ◽  
Rate Constant ◽  
Hydrogen Abstraction ◽  
Methyl Radicals ◽  
Arrhenius Parameters ◽  
Temperature Range

Hydrogen abstraction from H2S by CH3 radicals, produced by the photolysis of azomethane, has been studied in the temperature range 334-432 K. The rate constant, based on the value 1013.34 cm3 mol-1 s-1 for the recombination of CH3 radicals, is given by log k4 = (11.00 � 0.01) - (8760 � 80)/19.145T where k4 is in cm3 mol-1 s-1 and E is in J mol-1. The previous data reported for this reaction are discussed and best values for its Arrhenius parameters are recommended. The results indicate that CH3 radicals react faster than CF3 radicals with H2S; this confirms the importance of polar effects in the hydrogen abstraction reactions of CF3 radicals.

Reactions of methyl radicals. I. Hydrogen abstraction from dimethyl sulphide

1976 ◽  
Vol 29 (7) ◽  
pp. 1483 ◽  
Author(s):  
NL Arthur ◽  
M Lee
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Methyl Radicals ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen abstraction from (CH3),S and CH3COCH3 by CH3 radicals CH3+CH3SCH3 → CH4+CH3SCH2 CH3 + CH3COCH3 → CH4 + CH3COCH2 has been studied in the temperature range 120-245�. The rate constants, based on the value of 1013.34cm3 mol-l s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1, E in kJ mol-1, R = 0.008314 kJ K-1 mol-1): logk1 = (11.62 � 0.08) ? (38.35 � 0.68)/2.303RT logk3 = (11.61 � 0.05) ? (40.48 � 0.46)/2.303RT Combination of the results for (1) with thermochemical data gives a calculated value of Logk-1 = (11.8 -63.7/2.303RT for the rate constant of the reverse reaction. The results for CH3+(CH3)2S are compared with all of the available data for hydrogen abstraction by free radicals from both sulphur-containing compounds, and molecules of the type (CH3)xM.

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.

STUDIES ON HOMOGENEOUS FIRST ORDER GAS REACTIONS: IV. THE DECOMPOSITION OF PARA-n-BUTYRALDEHYDE AND PARA-ISOBUTYRALDEHYDE

1933 ◽  
Vol 9 (6) ◽  
pp. 603-609 ◽  
Author(s):  
C. C. Coffin
Keyword(s):  
Experimental Error ◽  
Degrees Of Freedom ◽  
Activation Energies ◽  
Energy Of Activation ◽  
Velocity Constant ◽  
First Order ◽  
Temperature Range ◽  
Measurable Rate ◽  
Gas Reactions ◽  
Internal Degrees Of Freedom

The gaseous decompositions of para-n-butyraldehyde and para-isobutyraldehyde to n-butyraldehyde and isobutyraldehyde respectively are homogeneous and first order over the pressure and temperature range investigated (1.3 to 55 cm. of mercury; 215 to 261 °C). Under these conditions the reactions go to completion at a measurable rate without complications. Within experimental error the activation energies of these reactions are equal and are approximately the same as that of the paracetaldehyde decomposition. This value is between 42,000 and 44,000 calories per mole. The rates of decomposition of the two parabutyraldehydes are very nearly the same at any temperature. At 500° abs. the velocity constant of the iso-compound is about 15% greater than that of the normal and about 100% greater than that of paracetaldehyde. The velocity constants at any temperature are given by the equations: para-n-butyraldehyde, [Formula: see text]; para-isobutyraldehyde, [Formula: see text]. The data are consistent with the idea that, for a series of reactions with the same energy of activation, an increase in the number of contributory internal degrees of freedom of a molecule will increase the probability of reaction.

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