Effects of CH3OH‐H2O and CH3OH solvents on rate of reaction of phthalimide with piperidine

Pseudo‐first‐order rate constants (k_obs) for the cleavage of phthalimide in the presence of piperidine (Pip) vary linearly with the total concentration of Pip ([Pip]_T) at a constant content of methanol in mixed aqueous solvents containing 2% v/v acetonitrile. Such linear variation of k_obs against [Pip]_T exists within the methanol content range 10%–∼80% v/v. The change in k_obs with the change in [Pip]_T at 98% v/v CH₃OH in mixed methanol‐acetonitrile solvent shows the relationship: k_obs = k[Pip]_T + k[Pip], where respective k and k represent apparent second‐order and third‐order rate constants for nucleophilic and general base‐catalyzed piperidinolysis of phthalimide. The values of k_obs, obtained within [Pip]_T range 0.02–0.40 M at 0.03 M NaOH and 20 as well as 50% v/v CH₃OH reveal the relationship: k_obs = k₀/(1 + {k_n[Pip]/k_OX[⁻OX]_T}), where k₀ is the pseudo‐first‐order rate constant for hydrolysis of phthalimide, k_n and k_OX represent nucleophilic second‐order rate constants for the reaction of Pip with phthalimide and for the XO⁻‐catalyzed cyclization of N‐piperidinylphthalamide to phthalimide, respectively, and [⁻OX]_T = [NaOH] + [⁻OX_re], where [⁻OX_re] = [⁻OH_re] + [CH₃O_re⁻]. The reversible reactions of Pip with H₂O and CH₃OH produce ⁻OH_re and CH₃O_re⁻ ions. The effects of mixed methanol‐water solvents on the rates of piperidinolysis of PTH reveal a nonlinear decrease in k with the increase in the content of methanol. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 29–40, 2001     

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

The 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 acetyl radicals CH3CO· and CD3CO· studied by flash photolysis and kinetic spectroscopy

Ultraviolet absorption spectra have been characterized for the acetyl-h₃ and acetyl-d₃ radicals, which were generated by the flash photolysis of the corresponding acetones. The spectra are broad and intense, with values of the extinction coefficient at the respective maxima estimated as: ?CH₃CO(215) = (1.0 ± 0.1) × 10⁴ L/mol·cm and ?CD₃CO(207.5) = (1.0 ± 0.05) × 10⁴ L/mol·cm. Rate constants for the reactions of mutual interaction were estimated as: k = 3.5 × 10¹⁰ L/mol·s and k = 3.4 × 10¹⁰ L/mol·s. Rate constants for the reactions of cross interaction were estimated as: k = 8.6 × 10¹⁰ L/mol·s and k = 5.2 × 10¹⁰ L/mol·s. The related values of the cross interaction ratios k/(kk)^1/2 = 2.6 and k/(kk)^1/2 = 1.6 do not differ significantly from the statistical value of 2. The participation of the radical displacement reactions was estimated in terms of the fractions k/k = 0.38 and k/k = 0.47. Corroborative spectra were obtained from the flash photolysis of methyl ethyl ketone and biacetyl, and the relative rates of the competing primary processes were estimated from the relative peak heights of the acetyl and methyl radicals in each system.     

Kinetics of the gas‐phase reaction of CF3CF2CH2OH with OH radicals and its atmospheric lifetime

CF₃CF₂CH₂OH is a new chlorofluorocarbon (CFC) alternative. However, there are few data about its atmospheric fate. The kinetics of its atmospheric oxidation, the OH radical reaction of CF₃CF₂CH₂OH, has been investigated in a 2‐liter Pyrex reactor in the temperature range of 298 ∼ 356 K using gas chromatography (GC)–mass spectrometry (MS) for analysis in this study. The rate coefficient of k₁ = (2.27) × 10⁻¹² exp[−(900 ± 70)/T] cm³ molecule⁻¹ s⁻¹ was determined using the relative rate method. The results are in good agreement with the literature values and the prediction of Atkinson's structure–activity relationship (SAR) model. From these results, the atmospheric lifetime of CF₃CF₂CH₂OH in the troposphere was deduced to be 0.34 year, which is 250 and 6 times shorter than those of CFC‐113 and hydrochlorofluorocarbons (HCFC‐225ca), respectively. Therefore CF₃CF₂CH₂OH has significant potential for the replacement of CFC‐113 and HCFC‐225ca. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 73–78, 2000     

Kinetics for the gas‐phase reactions of OH radicals with the hydrofluoroethers CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2 at 268–308 K

Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH₂FCF₂OCHF₂(k₁), CHF₂CF₂OCH₂CF₃ (k₂), CF₃CHFCF₂OCH₂CF₃(k₃), and CF₃CHFCF₂OCH₂CF₂CHF₂(k₄) by using a relative rate method. OH radicals were prepared by photolysis of ozone at UV wavelengths (>260 nm) in 100 Torr of a HFE–reference–H₂O–O₃–O₂–He gas mixture in a 1‐m³ temperature‐controlled chamber. By using CH₄, CH₃CCl₃, CHF₂Cl, and CF₃CF₂CF₂OCH₃ as the reference compounds, reaction rate constants of OH radicals of k₁ = (1.68) × 10^?12 exp[(?1710 ± 140)/T], k₂ = (1.36) × 10^?12 exp[(?1470 ± 90)/T], k₃ = (1.67) × 10^?12 exp[(?1560 ± 140)/T], and k₄ = (2.39) × 10^?12 exp[(?1560 ± 110)/T] cm³ molecule^?1 s^?1 were obtained at 268–308 K. The errors reported are ± 2 SD, and represent precision only. We estimate that the potential systematic errors associated with uncertainties in the reference rate constants add a further 10% uncertainty to the values of k₁–k₄. The results are discussed in relation to the predictions of Atkinson's structure–activity relationship model. The dominant tropospheric loss process for the HFEs studied here is considered to be by the reaction with the OH radicals, with atmospheric lifetimes of 11.5, 5.9, 6.7, and 4.7 years calculated for CH₂FCF₂OCHF₂, CHF₂CF₂OCH₂CF₃, CF₃CHFCF₂OCH₂CF₃, and CF₃CHFCF₂OCH₂CF₂CHF₂, respectively, by scaling from the lifetime of CH₃CCl₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 239–245, 2003     

Kinetic studies of the reactions CH2I2 + HI⇄CH3I + I2 and 2 CH3I⇄CH4 + CH2I2 the heat of formation of the iodomethyl radical

The rate of the reaction CH₂I₂ + HI ? CH₃I + I₂ has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k₁/M^?1 sec^?1) = 11.45 ± 0.18 - (15.11 ± 0.44)/θ. This value, combined with the assumption that E₂ = 0 ± 1 kcal/mole, leads to ΔH (CH₂I, g) = 55.0 ± 1.6 kcal/mole and DH (H? CH₂I) = 103.8 ± 1.6 kcal/mole. The kinetics of the disproportionation, 2 CH₃I ? CH₄ + CH₂I₂ were studied at 331° and are compatible with the above values.     

Kinetics and mechanism of the reaction of CH3O with NO

The kinetics of the reaction of CH₃O with NO and the branching ratio for HCHO product formation, obtained as Γ_HCHO = (Rate of HCHO formation) / (Rate of CH₃O decay), have been studied using a discharge flow reactor. Laser induced fluorescence has been used to monitor the decay of the CH₃O radical and the build-up of the HCHO product. Overall rate constants and product branching ratios were measured at room temperature over the pressure range of 0.72–8.5 torr He. Three reaction mechanisms were considered which differed in the routes of HCHO formation: (i) direct disproportionation; (ii) via an energized collision complex; or (iii) both reaction routes. It has been shown that data on the pressure dependence of the overall rate constant are not sufficient to distinguish between these mechanisms. In addition, an accurate value of Γ is required. Analysis of the available experimental data provided 0.0 and about 0.1 as the lower and upper limit for Γ, respectively. Since the rate constants derived for CH₃ONO formation were not sensitive to the value assumed for Γ, k = (1.69 ± 0.69) × 10^?29 cm⁶ molecule^?2 s^?1 and k = (2.45 ± 0.31) × 10^?11 cm³ molecule^?1 s^?1 could be derived. The rate constant obtained for formaldehyde formation when extrapolated to zero pressure is k = (3.15 ± 0.92) × 10^?12 cm³ molecule^?1 s^?1. © 1994 John Wiley & Sons, Inc.     

Nonlinear dynamics in the oxidations of substituted thioureas I: The reaction of 4‐methyl‐3‐thiosemicarbazide with acidic iodate [1]

The substituted thiourea, 4‐methyl‐3‐thiosemicarbazide, was oxidized by iodate in acidic medium. In high acid concentrations and in stoichiometric excess of iodate, the reaction displays an induction period followed by the formation of aqueous iodine. In stoichiometric excess of methylthiosemicarbazide and high acid concentration, the reaction shows a transient formation of aqueous iodine. The stoichiometry of the reaction is: 4IO + 3CH₃NHC(S)NHNH₂ + 3H₂O → 4I⁻ + 3SO + 3CH₃NHC(O)NHNH₂ + 6H⁺ (A). Iodine formation is due to the Dushman reaction that produces iodine from iodide formed from the reduction of iodate: IO + 5I⁻ + 6H⁺ → 3I₂(aq) + 3H₂O (B). Transient iodine formation is due to the efficient acid catalysis of the Dushman reaction. The iodine produced in process B is consumed by the methylthiosemicarbazide substrate. The direct reaction of iodine and methylthiosemicarbazide was also studied. It has a stoichiometry of 4I₂(aq) + CH₃NHC(S)NHNH₂ + 5H₂O → 8I⁻ + SO + CH₃NHC(O)NHNH₂ + 10H⁺ (C). The reaction exhibits autoinhibition by iodide and acid. Inhibition by I⁻ is due to the formation of the triiodide species, I, and inhibition by acid is due to the protonation of the sulfur center that deactivates it to further electrophilic attack. In excess iodate conditions, the stoichiometry of the reaction is 8IO + 5CH₃NHC(S)NHNH₂ + H₂O → 4I₂ + 5SO + 5CH₃NHC(O)NHNH₂ + 2H⁺ (D) that is a linear combination of processes A and B. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 193–203, 2000     

Iodine catalyzed pyrolysis of dimethyl sulfide. Heats of formation of CH3SCH2I,the CH3SCH2 radical,and the pibond energy in CH2S

A kinetic study has been made of the gas phase, I₂-catalyzed decomposition of (CH₃)₂S at 630–650 K. Some I₂ is consumed initially, reaching a steady-state concentration. The initial major products are CH₄ and CH₂S together with small amounts of CH₃SCH₂I, CH₃I, HI, and CS₂. The initial reaction corresponds to a pseudo-equilibrium: accompanied by: and which brings (I₂) into steady state and a final complex reaction: From the initial rate of I₂ loss it is possible to obtain Arrhenius parameters for the iodination: We measure k₁, (644 K) = 150 L/mol s and from both the Arrhenius plot and independent estimates A₁ (644 K) = 10^{11.2 ± 0.3} L/mol s. Thus, E₁ = 26.7 ± 1 kcal/mol. From the steady-state I₂ concentration, an assumed mechanism and the known rate parameters for the CH₃I/HI system. It is possible to deduce K_A (644) = 3.8 × 10^?2 with an uncertainty of a factor of 2. Using an estimated ΔS (644) = 4.2 ± 1.0 e.u. we find ΔH_A (644) = 7.0 ± 1.1 kcal. With 〈ΔC_PA〉644 = 1.2 this becomes: ΔH_A(298) = 6.6 ± 1.1 kcal/mol. Then ΔH (CH₃SCH₂I) = 6.3 ± 1 kcal/mol. Making the assumption that E_?1 = 1.0 ± 0.5 kcal/mol we find ΔH (644) = 25.7 ± 0.7 kcal/mol and with 〈ΔC_PI〉 = 1.2; ΔH = 25.3 ± 0.8 kcal/mol. This gives ΔH (CH₃S?H₂) = 35.6 ± 1.0 kcal/mol and DH (CH₃SCH₂? H) = 96.6 ± 1.0 kcal/mol. This then yields E_π(CH₂S) = 52 ± 3 kcal. From the observed rate of pressure increase in the system and the preceding data k₃, is calculated for the step CH₃SCH₂ → CH₃ + CH₂S. From an estimated A-factor E₃ is deduced and from the overall thermochemistry values for k_?3 and E_?3. A detailed mechanism is proposed for the I-atom catalyzed conversion of CH₂S to CS₂ + CH₄.     

Rate constants for some reactions of free radicals with haloacetates in aqueous solution

The kinetics of the acqueous-phase reactions of the free radicals ·OH, ·Cl, and SO· with the halogenated acetates, CH₂FCOO^?, CHF₂COO^?, CF₃COO^?, and with CH₂ClCOO^?, CHCl₂COO^?, CCl₃COO^? were investigated. Generally, the reactivity decreases with increasing halogen substitution and is in the order k(·OH) > k(SO·) > k(·Cl), but there is no general relation between the effect on reactivity of chlorine and fluorine substitution. © 1995 John Wiley & Sons, Inc.     

The elimination of HF from vibrationally excited fluoroethanes. The decomposition of 1,1,1-trifluoroethane-d0 and d3

The vibrationally excited molecules CF₃CH and CF₃CD have been synthesized by radical combination (produced by ketone photolysis), and HF and DF elimination from them studied as a function of temperature and pressure. Using RRK theory many calculations have recently been made of critical energies for the decomposition of "hot" fluoroethane molecules. Taking CF₃CH as an example, it is concluded that the empiricism involved in such calculations renders results of doubtful significance. The non-equilibrium kinetic isotope effect is k_H/k_D = 3.1 at 470°K. Arrhenius parameters are also presented for radical abstraction reactions from the ketone source molecules.     

The decomposition kinetics of chemically activated methyl-d1-methylsilane-d2 and ethylsilane-d3

The decomposition kinetics of chemically activated methyl-d₁-methylsilane-d₂ (DMS-d) and ethylsilane-d₃ (ES-d) from the Si-D and C-H insertion reactions of CH₂ (¹A₁) with methylsilane-d₃ have been studied. The total rate constants for decomposition of chemically activated DMS-d₃ and ES-d₃ have been measured. The individual rate constants for molecular elimination of CH₃D, CH₂D₂, and D₂ from DMS-d and for molecular elimination of CH₃CH₂D and D₂ from ES-d have been measured. All of the above rate constants exhibit the expected kinetic isotope effect when compared to those found previously in the undeuterated system. RRKM theory calculations of the rate constants for the expected C-Si and Si-D bond rupture processes, based on energetics and activated comple× models deduced previously for the undeuterated system, were carried out. In the case of DMS-d the RRKM theory calculations of rate constants for the bond rupture processes combined with experimental rate constants for the molecular elimination processes gave a total rate constant for decomposition in agreement with the measured value. The results of a high-pressure study of the CH₃D/CH₂D₂ ratio from chemically activated DMS-d₃ decomposition were consistent with complete randomization of internal energy up to a pressure of 4 atmospheres (lifetime of ～1.7 × 10^×11 sec). This is not an unexpected result in light of earlier work.     

Comparison of the kinetics of cathodic H2 evolution from the unhydrated H3O+ ion and its hydrated form H9O: Frequency factor effects and modes of activation

Experiments are described in which the kinetics of cathodic hydrogen evolution from the unhydrated H₃O⁺ ion in pure CF₃SO H₃O⁺ are compared with those from an aqueous solution of CF₃SO₃H where the proton is mainly in a fully hydrated state as H₉O. From the acid hydrate, which exists mainly as the ionic compound CF₃SOH₃O⁺, rates of H₂ evolution at Ni, Pt, and Hg electrodes, measured at a given overpotential or expressed as exchange current densities, are between about 3.5 and 20 times slower than those from the same electrolyte in dilute (1.0M) aqueous solution. Allowing for the concentration differences in these two types of system and double-layer effects, the rate constants are between about 9.4 and 216 times smaller for the reaction from H₃O⁺ than from H₉O at the above electrodes. The evaluation of apparent heats of activation for H₂ evolution from the two types of proton sources allows ratios of real frequency factors to be calculated for discharge from H₃O⁺ and H₉O. These data have a bearing on the theoretical conclusions regarding proton discharge mechanisms and show that frequency factor effects can be as important as activation energy differences in determining the rates of proton discharge from different proton sources. The results are discussed in terms of current ideas about electron and proton transfer in electrochemical reactions, the state of hydration of H⁺, and the role of discharge from paired CF₃SO and H₃O⁺ ions. In particular, the molecular mechanics of discharge of the proton from the molecular ion H₃O⁺ can be different from that from the fully hydrated H⁺ ion where many more HO- vibrational and librational modes can be involved in the process of activation of the H₉O entity.     

Persulfate and perphosphate oxidation of 2-propanol: A relative rate study

A competitive reaction study for two isoelectronic peroxides (peroxodisulfate S₂O and peroxodiphosphate P₂O) interacting with the free radical ·Clpar;CH₃)₂OH is described. The radical formation is initiated by photolysis, the amounts of peroxide remaining analyzed volumetrically. It is found that persulfate reacts with the organic radical over 100 times more rapidly than does perphosphate. Mechanistic consequences in relation to previous work are briefly discussed.     

Gas phase rate coefficients and activation energies for the reaction of butanal and 2‐methyl‐propanal with nitrate radicals

Rate coefficients have been determined for the reaction of butanal and 2‐methyl‐propanal with NO₃ using relative and absolute methods. The relative measurements were accomplished by using a static reactor with long‐path FTIR spectroscopy as the analytical tool. The absolute measurements were made using fast‐flow–discharge technique with detection of NO₃ by optical absorption. The resulting average coefficients from the relative rate experiments were k = (1.0 ± 0.1) × 10⁻¹⁴ and k = (1.2 ± 0.2) × 10⁻¹⁴ (cm³ molecule⁻¹ s⁻¹) for butanal and 2‐methyl‐propanal, respectively. The results from the absolute measurements indicated secondary reactions involving NO₃ radicals and the primary formed acyl radicals. The prospect of secondary reactions was investigated by means of mathematical modeling. Calculations indicated that the unwanted NO₃ radical reactions could be suppressed by introducing molecular oxygen into the flow tube. The rate coefficients from the absolute rate experiments with oxygen added were and k = (1.2 ± 0.1) × 10⁻¹⁴ and = (0.9 ± 0.1) × 10⁻¹⁴ (cm³ molecule⁻¹ s⁻¹) for butanal and 2‐methyl‐propanal. The temperature dependence of the reactions was studied in the range between 263 and 364 K. Activation energies for the reactions were determined to 12 ± 2 kJ mole⁻¹ and 14 ± 1 kJ mole⁻¹ for butanal and 2‐methyl‐propanal, respectively. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 294–303, 2000     

Kinetics of the gas‐phase reaction of Cl atoms with CF2ClCFClH at 263–313 K

Relative rate techniques were used to measure k(Cl + CF₂ClCFClH) = (1.4) × 10⁻¹¹ exp[−(2360 ± 400)/T] cm³ molecule⁻¹ s⁻¹; k(Cl + CF₂ClCFClH) = 5.1 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹ at 298 K. This result is discussed with respect to the available data. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 785–788, 1999     

Kinetics and mechanism of electron transfer from phenolate anion to hexacyanoferrate (III) in aqueous alkaline media

A kinetic reinvestigation of the title redox system in aqueous alkaline media at 35°C and an ionic strength of 0.5 mol dm^?3 shows that the reaction follows a pseudosecond-order Fe(CN) disappearance. While varying [phenol]₀ and [OH^?] exhibit a linear influence on the pseudo-second-order rate constant, varying[Fe(CN)]₀ and [Fe(CN)]₀, initially taken, have a complicated inhibitory effect on the same. The major phenoloxidation products isolated under a chosen condition are 2,2′- and 4,4′- dihydroxydiphenyl. Results are interpreted in terms of a probable mechanism which envisages a reversible formation, by the first one-electron transfer, of a reactive phenoxy radical (PhO^˙) which on the second one-electron transfer forms a less reactive ion-pair intermediate (stabilized by the Fe(CN) produced) to decompose rate-determiningly to phenoxonium cation (PhO⁺) and Fe(CN), the product-formation steps being very rapid and kinetically indistinguishable.     

CH bond dissociation energies,isolated stretching frequencies,and radical stabilization energy

An earlier correlation between isolated CH stretching frequencies, v, and experimental CH bond dissociation energies, in hydrocarbons, fluorocarbons, and CHO compounds, is updated. A stabilization energy, E, which reflects only the properties of the radical, is defined by the deviation of a point from the above correlation. E values for a variety of radicals are listed and discussed. In H? C? N and H? C? O compounds E is low or negligible, due to the low v found in these compounds. The conventional definition of E_S then represents a serious misnomer, which distracts attention from the probable source of discrepancies between experimental and ab initio values of DH°(C? H), namely, the parent molecules. Stereo electronic effects concerned with the breaking of CH bonds are predicted in a variety of situations. Some experimental determinations of DH°(C? H), viz., in C₂H₄, HCOOH, CH₃CHO, CH₃NH₂, are considered to be probably in error. Schemes for partitioning energies of atomization into ‘standard’ or ‘intrinsic’ bond energies are criticized.     

Thermochemistry and kinetics of the reaction of methyl mercaptan with iodine

The gas-phase reaction CH₃SH + I₂ has been studied spectrophotometrically over the temperature range of 476–604 K. It was found that the reaction undergoes H abstraction by I at ≤575 K, leading to the formation of MeSI and followed by a secondary reaction which leads to the formation of MeSSMe: Taking into consideration the effect of reaction (2), the equilibrium constant K₁ (554 K) has been evaluated to be 0.025 ± 0.004. This value was combined with the estimated values S (CH₃SI, g) = 73.7 ± 1.0 eu and 〈ΔC〉 = 0.87 ± 0.3 eu to obtain ΔH = 4.03 ± 0.73 kcal/mol. This yields ΔH (CH₃SI, g) = 7.16 ± 0.73 kcal/mol when combined with known thermochemical values for CH₃SH, HI, and I₂. A kinetic study was vitiated by the concurrent heterogeneous reaction of MeSH and I₂ at lower temperatures and the rather complicated chemistry occurring at elevated temperatures. However, attempts at measuring rate constants at 554 K lead to a lower limit of ΔH (CH₃S·, g) ≥ 29.5 ± 2 kcal/mol when an estimated value of A = 10^{10.8 ± 0.2} L/mol·s for the reactionc is used. DH (CH₃S–I) is estimated to be 49.3 ± 1.7 kcal/mol. The bond strengths of some divalent sulfurs and the reaction mechanisms are discussed. A crude estimate of DH⁰(H–CH₂SH) = 96 ± 1 kcal has been obtained from the kinetic data.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.