bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen‐abstraction reactions from organosilicon compounds. The reactions of methyl, trideuteromethyl, trifluoromethyl, and ethyl radicals with tetramethylsilane
Authors: Kerr J. A. , Stephens A. , Young J. C. 
Published: January 2005

AbstractThe following Arrhenius parameters have been determined for the hydrogen‐abstraction reactions:
R + (CH3)4Si → RH + (CH3)3SiCH3

R
Temp. (°K)
E (kcal/mole)
Log A (mole−1 cc sec−1)
Log k(400°K) (mole−1 cc sec−1)

CF3
330–433
7.23 ± 0.09
11.90 ± 0.05
7.95

CH3
396–476
10.23 ± 0.36
11.55 ± 0.18
5.68

CD3
396–496
10.36 ± 0.12
11.84 ± 0.06
6.20

C2H5
423–522
11.40 ± 0.48
11.88 ± 0.22
5.68

The activation energies are in keeping with the strengths of the bonds formed during the reaction. By comparison with the activation energies for the analogous reactions of neopentane it is estimated that D((CH3)3SiCH2H) ≃ 97 kcal/mole.The A factors for the above series of reactions fall within the range predicted by transition‐state theory for this type of process and the validity of previous results of Kerr, Slater, and Young is seriously in doubt.
Hydrogen abstraction reactions from organosilicon compounds. The reactions of methyl, trifluoromethyl, and ethyl radicals with trichlorosilane
Authors: Kerr J. A. , Stephens A. , Young J. C. 
Published: January 2005

AbstractArrhenius parameters have been determined for the hydrogen‐abstraction reactions:
R + SiHCl3 + RH + SiCl3

R
Temp (°K)
E(kcal/mole)
Log A(mole−1 cc sec−1)
Log k(400°K) (mole−1 cc sec−1)

CF3
323–461
5.98 ± 0.06
11.77 ± 0.03
8.50

CH3
333–443
4.30 ± 0.08
10.83 ± 0.04
4.48

C2H5
314–413
5.32 ± 0.07
11.54 ± 0.04
8.63

The trend in activation energies E < E < E is interpreted as indicating a polar effect in the reaction of CF3 with SiHCl3 and the similar reactivities of all three radicals appear to be due to the high exothermicity of the reactions.The A Factors for the reactions are normal for hydrogen abstraction reactions of free radicals. The previous results of Kerr, Slater, and Young for CH3 abstracting an H atom from SiHCl3 have been amended.
The kinetics and thermochemistry of S2F10 pyrolysis
Authors: Benson Sidney W. , Bott Jerry 
Published: January 2005

AbstractData on the kinetics of S2F10 pyrolysis, which gives SF4 + SF6, have been reinterpreted to give a value for the equilibrium constant of S2F10 ⇆ SF4 + SF6. This, together with statistical estimates of the entropy and heat capacity of S2F10, can be used to give for this reaction values of ΔH = 19.7 ± 1.0 kcal/mole and ΔS = 47.6 ± 2 gibbs/mole. ΔH(S2F10) = –494 kcal/mole. A compatible mechanism is shown to be
S2F10 ⇆ 2SF5 (fast); 2SF5 ⇆ SF6 + SF4 (slow)
with step 2 rate‐determining. The overall, best first order rate constant is proposed as kmeas = 1017.42–43.0/θ sec−1 = K1k2, where θ = 2.303RT in kcal/mole.Independent measurements of δH and S° for the SF5 radical, permits the evaluation of the equilibrium constant K1 = 108.92–(27.1 ± 6)/θ l./mole‐sec and yields k2 = 108.50–15.9/θ l./mole‐sec. The observed homogeneous catalysis by NO and CHCl  CHCl can be explained in terms of a direct abstraction of F from S2F10 : C + S2F10 → CF + S2F9, followed by S2F9 → SF5 + SF4 and SF5 + CF ⇆ SF6 + C (C  NO or C2H2Cl2).
On the thermal decomposition of COS
Authors: Schecker H. G. , Wagner H. Gg. 
Published: January 2005

AbstractThe thermal dissociation of COS was investigated in shock waves with argon as carrier gas. The concentration was varied between 0.05 and 0.5% COS in argon, the total density from 2.5 × 10−5mole/cm3to 2.5 × 10−3mole/cm3. Temperatures between 1500°K and 3100°K were applied.For the reactionthe rate constant was found to bein the low pressure range of the unimolecular reaction andin the high pressure range.
Rate and mechanism of thermal decomposition of 4‐methyl‐l‐pentyne in a single‐pulse shock tube
Authors: Tsang Wing 
Published: January 2005

AbstractDilute mixtures of 4‐methyl‐l‐pentyne have been pyrolyzed in a single‐pulse shock tube. The decomposition process involves bond breaking:

as well as a molecular reaction:

The rate parameters are:

The heat of formation of propynyl radical is thus ΔHf300 = 338 kJ mol−1 (80.7 kcal mol−1)˙ This leads to a propynyl resonance energy of 40 kJ mol−1 (9.6 kcal mol−1).
Reactions of atomic nitrogen and atomic hydrogen with methylacetylene
Authors: Solomon W. C. , Homann K. H. , Warnatz J. H. 
Published: January 2005

AbstractThe reaction of nitrogen atoms with methylacetylene has been studied using a fast‐flow low‐pressure reactor coupled to a mass spctrometer by a nozzle‐beam sampling system. Hydrogen atom concentrations were measured by ESR analysis. Experimental second‐order rate constants for the consumption of N atoms, of C3H4, and for the formation of N2 were determined in the temperature range of 283° to 485°K. Product profiles of all stable species and of hydrogen atoms and methyl radicals were obtained for different initial concentrations of the reactants. Two different reaction pathways can be distinguished: one provides for recombination of N atoms, and the second leads to the formation of cyano compounds and other hydrocarbons. Only the latter process is influenced by the addition of hydrogen atoms. Mechanisms for the two pathways are discussed.
Chlorine‐photosensitized oxidations of chloroethanes and chloroethylenes in the gas phase
Authors: Bertrand L. , Exsteen‐Meyers L. , Franklin J. A. , Huybrechts G. , Olbregts J. 
Published: January 2005

AbstractLong‐chain chlorine‐photosensitized oxidation has been observed in the gas phase at about 355°K for 1,1,2,2‐ and 1,1,1,2‐C2H2Cl4, C2HCl5, and C2Cl4 but not for C2H6, 1,2‐C2H4Cl2, 1,1,1‐C2H3Cl3, C2H4, and 1,2‐C2H2Cl2. This is shown to depend on the exothermicity of the dissociation of the chloroethoxy radicals which must be involved in each reaction system.
Quenching cross sections for the deactivation of metastable mercury 6 (3P0)
Authors: Campbell J. M. , Penzes S. , Sandhu H. S. , Strausz O. P. 
Published: January 2005

AbstractBy monitoring the relative concentrations of mercury 3P0 atoms using absorption photometry, absolute rate constants have been measured for the excimer‐forming reaction Hg (3P0) + Hg + N2 → Hg2* + N2 and for the quenching of Hg (3P0) atoms by ethane, propane, deuterated propanes, and nitrous oxide.
The pyrolysis of neopentane at small extents of reaction
Authors: Baronnet F. , Dzierzynski M. , Côme G. M. , Martin R. , Niclause M. 
Published: January 2005

AbstractThe pyrolysis of neopentane, at small extents of reaction, was studied by gas chromatography, in Pyrex reaction vessels between 450° and 530°C and in the initial pressure range 25–200 mm Hg. At initial time, this thermal decomposition can be essentially represented by a homogeneous long‐chain radical mechanism. The rate constant of the unimolecular initiation process is approximately given by the expression

The initial rate constant of the global reaction (order 3/2) is nearly equal to

This reaction is strongly inhibited by propene or isobutene and self‐inhibited by the isobutene formed; an interpretation of all these inhibition phenomena of the neopentane pyrolysis is proposed. Our observations and conclusions, which have been summarized in communications during 1968 and 1969, are compared to those of other authors, particularly to the recent ones of Purnell and colleagues [13] and of Taylor and colleagues [14], [15].
Very low‐pressure pyrolysis. IV. The decomposition of i‐propyl iodide and n‐propyl iodide
Authors: King Keith D. , Golden David M. , Spokes G. Neil , Benson Sidney W. 
Published: January 2005

AbstractThe decomposition rate constant of i‐PrI under conditions of very low‐pressure pyrolysis (VLPP) is completely consistent with the well‐known high‐pressure Arrhenius parameters and the RRK(M) theory. The decomposition of n‐PrI under the same conditions proceeds via two pathways, the anti‐Markownikoff dehydroiodination and CI bond scission. The data, analyzed by taking into account the mutual interaction of the two pathways, is completely consistent with the known Arrhenius parameters for the bond scission step and, when combined with a reasonable A‐factor, yields an activation energy for HI elimination which is as predicted for these semi‐ion pair transition states.
Kinetics of the gas phase reaction of methyl benzoate with bromine and iodine: The methoxyl CH bond strength of methyl esters
Authors: Solly Richard K. , Benson Sidney W. 
Published: January 2005

AbstractThe gas phase reactions of PhCOOCH3 with I2 and Br2 were studied spectrophotometrically in a static system over the temperature ranges 344–359° and 246–303°, respectively. For each system the initial rate was first order in PhCOOCH3 and half order in halogen as the concentration of PhCOOCH3 was varied from 1.4 to 15.2 torr, that of I2 from 6.2 to 26.4 torr, and that of Br2 from 3.0 to 13.6 torr. The rate‐determining step is the extraction of a methoxyl hydrogen atom: magnified image Empirical assignment of A‐factors for k1 lead to

for the I2 system, and to

for the Br2 system, where ϕ = 2.303RT in kcal/mole. Combined with the assumption that E–1 = 1 ± 1 kcal/mole and 2 ± 1 kcal/mole for HI and HBr, respectively, DH (PhCOOCH2H) calculated from the two systems shows excellent agreement at 100.2 ± 1.3 kcal/mole and 100.1 ± 1.3 kcal/mole. Using a value of δH (PhCOOMe) = –65.6 ± 1.5 kcal/mole obtained from group additivity estimates, δHf,2980 (PhCOOCH2) is calculated to be –16.7 ± 2.0 kcal/mole. Unimolecular decomposition of the Ph(CO)O°CH2 radical was also observed:

with a rate constant equal to

The abnormally high methoxyl CH bond strength is discussed in relation to the bonding in ethers, alkanes, and esters.
A quantitative study of alkyl radical reactions by kinetic spectroscopy. II. Combination of the methyl radical with the oxygen molecule
Authors: Basco N. , James D. G. L. , James F. C. 
Published: January 2005

AbstractThe kinetics of the reaction

have been studied, using the technique of flash photolysis and kinetic spectroscopy to follow the methyl radical concentration. The order of the reaction lies between 2 and 3 throughout the range of pressure from 25 to 380 torr at 22°C, and the results are consistent with a single reaction sequence:

The limiting values of the third‐order rate coefficients at low pressures are (3.6±0.3) × 1011 1.2 mole−2 sec−1 when M is neopentane, and (0.94 ± 0.03) × 1011 1.2 mole−2 sec−1 when M is nitrogen. The limiting value of the second‐order rate coefficient at high pressures is (3.1 ± 0.3) × 108 1. mole−1 sec−1. The rate constant for the independent second‐order reaction

is shown to be not much greater than 2 × 105 1. mole−1 sec−1, so that this reaction does not complete significantly with the combination reaction.This new interpretation is contrary to currently accepted views.
The Competitive dehydrohalogenation of 1,1,1‐trifluoro‐2‐chloroethane in reflected shock waves
Authors: Millward G. E. , Tschuikow‐Roux E. 
Published: January 2005

AbstractThe thermal decomposition of 1,1,1‐trifluoro‐2‐chloroethane has been investigated in the single‐pulse shock tube between 1120° and 1300deg;K at total reflected shock pressures from ∼2610 to 3350 torr. Under these conditions, the major reaction is the α,α‐elimination of hydrogen chloride,

with

The decomposition also involves the slower α,β‐elimination of hydrogen fluoride,

with the first‐order rate constant given by

At temperatures above 1270°K, two additional minor products were observed. These were identified as CF2CFCl and CF3CHCl2 and suggest CCl rupture as a third reaction channel leading to complicated kinetics.
The mechanism of thermal dehydrochlorination. Pyrolysis of 1‐Chloro‐1‐fluoroethane and 1‐chloro‐1, 1‐difluoroethane
Authors: Martens G. J. , Godfroid M. , Decelle R. , Verbeyst J. 
Published: January 2005

AbstractThe thermal decompositions of 1‐chloro‐1‐fluoroethane and 1‐chloro‐1,1‐difluorethane at atmospheric pressure have been studied in the temperature range 500–600°C in a flow system. The dehydrochlorinations are homogenous in a carbonaceous reactor and unimolecular. The rate constants are given by

and

The criteria for molecular or chain processes in thermal dehydrochlorinations are discussed.
A study of the bimolecular intersystem crossing reaction induced in the first excited singlet of SO2 by collisions with O2 and other atmospheric gases
Authors: Wampler Fred B. , Calvert Jack G. , Damon Edward K. 
Published: January 2005

AbstractThe relative intensities of phosphorescence of SO2(3B1) molecules have been determined following the optical excitation of SO2(1B1) molecules by a 2662 Å laser pulse. From a kinetic treatment of these measurements, the intersystem crossing ratio, k2b/(k1b + k2b), was determined; SO2(1B1) + M → SO2(3B1) + M (2b); SO2(1B1) + M → SO2 + M (1b). With M = O2, N2, Ar, CO2, and CO, k2b/(k1b + k2b) = 0.030 ± 0.013, 0.034 ± 0.029, 0.025 ± 0.005, 0.052 ± 0.014, and 0.045 ± 0.028, respectively. These data allow a new, more quantitative evaluation of the extent of involvement of the “excess” triplet SO2 in the 3130 Å‐irradiated mixtures of SO2 and CO at high pressures [5, 6]. The new data are also of direct interest in the determination of the theoretical maximum rates of photooxidation of SO2 in the sunlight‐irratiated atmosphere of the earth.
The kinetics reaction of 1‐chloro‐2,3‐epoxypropane with n‐butyl and iso‐butyl alcohols
Authors: Novák Jiří 
Published: January 2005

AbstractThe reactions of 1‐chloro‐2,3‐epoxypropane with n‐butyl and isobutyl alcohols and their 3‐chloro‐2‐hydroxypropyl ethers, respectively, in the presence of boron fluoride diethyl etherate catalyst are of the first order with regard to 1‐chloro‐2,3‐epoxypropane as well as to the catalyst. In the catalyst concentration range of 1.4 to 47.3 mmol/l., the participation of the catalyst in the reaction is incomplete. The mechanism of the reactions resembles SN2 in regard to changes of activation entropy and influence of dielectric constant of the reaction medium upon the reaction rate. The established values of K (the ratio of propagation to initiation rates) are suitable for calculating the compositions of the adducts obtained. The experimentally obtained yields of 3‐chloro‐2‐hydroxypropyl ethers of lower alcohols are compared with those calculated from the kinetically determined values of K.
Analysis of the kinetics of the thermal and chemically activated elimination of HF from 1,1,1‐trifluoroethane: the CC bond dissociation energy and the heat of formation of 1,1,1‐trifluoroethane
Authors: Rodgers Alan S. , Ford W. G. F. 
Published: January 2005

AbstractThe thermal, unimolecular elimination of HF from CH3CF3 was studied by three different groups over the temperature range 1000° to 1800°K. While the reported kinetic parameters varied greatly, it is shown here that these data may be satisfactorily correlated in terms of a four‐center transition state. This correlation results in ΔE = 69.2 kcal/mol, and log (k/s−1) = 14.6 – 72.6/θ. These results may then be combined with the kinetics of the chemically activated elimination of HF from CH3CF3 formed by the recombination of methyl and trifluoromethyl radicals. The data from three different laboratories are shown to be in excellent agreement. These data, combined with extant thermal data, yield as a best value DH(CH3CF3) = 99.6 ± 1.1 kcal/mol. This gives the unexpectedly high value of DH298°(CH3CF3) = 101.2 ± 1.1 kcal/mol. It is suggested that dipoledipole interactions, primarily in CH3CF3, account for this surprisingly strong CC bond dissociation energy. These results also yield δH(CH3CF3; g, 298) = −178.6 ± 1.5 kcal/mol.
The gas‐phase kinetics of the reaction of 1,1,1‐trifluoroethyl iodine with HI: The CI bond dissocation energy in 2,2,2‐trifluoroethyl iodide
Authors: Wu E‐Chung , Rodgers A. S. 
Published: January 2005

AbstractThe kinetics of the gas‐phase reaction of 2,2,2‐trifluoroethyl iodide with hydrogen iodide has been studied over the temperature range of 525°K to 602°K and a tenfold variation in the ratio of CF3CH2I/HI. The experimental results are in good agreement with the expected free radical‐mechanism:

An analysis of the kinetic data yield:

where θ =2.303RT in kcal/mol. If these results are combined with the assumption that E2 = 0 ± 1 kcal/mol, then one obtains DH (CF3CH2I) = 56.3 kcal/mol. This result may be compared with DH(CH3CH2I) = 52.9 kcal/mol and suggests that substitution of three fluorines for hydrogen in the beta position strengthens the CI bond slightly.
Anchimeric assistance in vapor‐phase acetate thermolysis
Authors: Kramer Daniel J. , Smith Grant Gill 
Published: January 2005

AbstractThe occurrence of anchimeric assistance in the vapor‐phase thermolysis of anti‐ and syn‐7‐acetoxy‐7‐methylnorbornene and 7‐acetoxy‐7‐methylnorborane has been investigated. The relative rates of thermolysis were found to be 1.9, 0.87, and 1.0, respectively. The nature of the transition state for ester thermolysis is discussed in light of the small amount of anchimeric assistance found in the thermolysis of the anti‐isomer.
Decomposition of chemically activated ethyltrimethylgermane the arrhenius A‐factors for rupture of group IVA—methyl bonds
Authors: Scott R. L. , Richardson A. E. , Simons J. W. , Hase W. L. 
Published: January 2005

AbstractThe decomposition rate of chemically activated ethyltrimethylgermane from the reaction 1CH2 + (CH3)4Ge, where 1CH2 was produced from diazomethane photolysis at 3660 Å, is 8.6 × 105 sec−1. This result combined with RRKM theory and critical energy estimates yields an Arrhenius A factor of log[A (sec−1)/methyl] = 14.7 ± 0.8 for methyl rupture from germanium.Log A values for methyl rupture from carbon, silicon, and germanium linearly correlate with the vibrational‐rotational entropies of the corresponding tetramethyls. Extrapolation predicts log[A (sec−1)/methyl] = 14.4 and 14.3 for methyl rupture from tin and lead, respectively.
Pyrolysis of tetrafluorohydrazine
Authors: Corbin Warren , Levy Joseph B. 
Published: January 2005

AbstractThe pyrolysis of tetrafluorohydrazine has been studied from 578 to 791°K. The stoichiometry has been established as

Reaction rates have been measured and the effects of surface area, inert gas pressure, and nitric oxide have been examined. The rate‐determining step proposed is

and the general rate expression obtained for this is
A kinetic study of the reaction of O(3P) with toluene
Authors: Furuyama Shozo , Ebara Nozomu 
Published: January 2005

AbstractThe absolute rate constant of the reaction of O(3P) with toluene was measured by the microwave discharge‐fast‐flow method to obtain kT = 109.7–2.7/2.303RT l./mole·sec at 100–375°C. This was in good agreement with the rate constant calculated from the combination of the relative rate constant obtained by Jones and Cvetanovic with the recently determined absolute rate constants of the reaction of O(3P) + olefins. The extrapolation of the above Arrhenius plot to 27°C was also in good agreement with the absolute value of kT = 4.5 × 107 l./mole·sec determined recently by Atkinson and Pitts at 27°C. The rate constant of the reaction of chlorobenzene with O(3P), obtained at 238°C as 108.3 l./mole·sec by a competitive method, was smaller than kT by a factor of about two at the same temperature.
The very‐low‐pressure pyrolysis (VLPP) of n‐propyl nitrate, tert‐butyl nitrite, and methyl nitrite. Rate constants for some alkoxy radical reactions
Authors: Mendenhall G. David , Golden David M. , Benson Sidney W. 
Published: January 2005

AbstractThe pyrolysis of n‐propyl nitrate and tert‐butyl nitrite at very low pressures (VLPP technique) is reported. For the reaction the high‐pressure rate expression at 300°K, log k1 (sec−1) = 16.5 − 40.0 kcal/mole/2.3 RT, is derived. The reaction was studied and the high‐pressure parameters at 300°K are log k2(sec−1) = 15.8 − 39.3 kcal/mole/2.3 RT. From ΔS1,−10 and ΔS2,−20 and the assumption E−1 and E−2 ⋍ 0, we derive log k−1(M−1·sec−1) (300°K) = 9.5 and log k−2 (M−1·sec−1) (300°K) = 9.8. In contrast, the pyrolysis of methyl nitrite and methyl d3 nitrite afford NO and HNO and DNO, respectively, in what appears to be a heterogeneous process. The values of k−1 and k−2 in conjunction with independent measurements imply a value at 300°K for of 3.5 × 105 M−1·sec−1, which is two orders of magnitude greater than currently accepted values.In the high‐pressure static pyrolysis of dimethyl peroxide in the presence of NO2, the yield of methyl nitrate indicates that the combination of methoxy radicals with NO2 is in the high‐pressure limit at atmospheric pressure.
An absolute measurement of the rate constant for t‐butyl radical combination
Authors: Choo K. Y. , Beadle P. C. , Piszkiewicz L. W. , Golden D. M. 
Published: January 2005

AbstractThe rate constant for tert‐butyl radical recombination has been measured near 700°K by the very‐low‐pressure pyrolysis (VLPP) technique and was found to be 108.8±0.3 M−1·sec−1 with neglibible temperature dependence. The thermochemical parameters for tertbutyl radicals were varied within reasonable limits to bring into agreement the data for the decomposition of 2,2,3,3‐tetramethyl butane and the recombination of tert‐butyl radicals. The revised thermochemistry also makes the gas‐phase results and liquid‐phase results compatible.
A kinetic study of the oxidation of α‐hydroxy acids and α‐hydroxy ketones by potassium bromate
Authors: Natarajan R. , Venkatasubramanian N. 
Published: January 2005

AbstractThe oxidation of α‐hydroxy acids and α‐hydroxy ketones by Br(V) follows the rate‐law

However, the former reaction exhibits a second‐order dependence on hydrogen ion concentration while the latter reaction has a third‐order dependence. A mechanism involving a slow formation of a bromate ester of the α‐hydroxy acid followed by a fast decomposition is proposed. A rate‐determining formation of a bromate ester from the conjugate acid of benzoin, followed by a rapid decomposition of the bromate ester, explains the kinetic data for the oxidation of benzoin.
The reactions of ozone with methyl and ethyl nitrites
Authors: Hastie D. R. , Freeman C. G. , McEwan M. J. , Schiff H. I. 
Published: January 2005

AbstractThe reactions of O3 with CH3ONO and C2H5ONO were studied using infrared absorption spectroscopy in a static reactor at temperatures between 298 and 352K. Both reactions followed simple second‐order kinetics forming the corresponding nitrate:

equation image

The rate coefficients are given by

.
The isomerization of cycloheptatriene at high temperatures
Authors: Gaynor Brendan J. , Gilbert Robert G. , King Keith D. , Mackie John C. 
Published: January 2005

AbstractThe isomerization of cycloheptatriene at high temperatures (800–1250°K) has been studied experimentally using a shock tube at high pressures and by very low‐pressure pyrolysis in the intermediate‐pressure region (the first direct use of the latter technique for an isomerization). Rate coefficients obtained are in accord with previous results at lower temperatures. The results are examined theoretically to account for weak‐collision nonequilibrium effects. These corrections are found to be appreciable at the temperatures studied.
Unimolecular decomposition of chemically activated methylallylether
Authors: Ibuki Toshio , Takezaki Yoshimasa 
Published: January 2005

AbstractThe unimolecular decomposition of chemically activated methylallylether (MAE) formed by the cross combination of methoxymethyl and vinyl radicals was studied in the gas phase. The experimentally determined rate constant was found to be 1.11 × 108 sec−1 at 9.6°C for the decomposition of MAE into propene and formaldehyde. The decomposition of MAE via the six‐center retro‐“ene” type transition state is analyzed by using the RRKM unimolecular reaction theory. For the molecular parameter assignments of energized MAE, a model which contains one internal rotational mode is supported, and MAE decomposition is characterized by a tight complex model. The best agreement between experimental and theoretical results was found when a critical energy of 40.1 kcal/mol was used.