Rate Constants For Addition Research Articles

Selective Free Radical Reactions using Supercritical Carbon Dioxide

We report herein a means to modify the reactivity of alkenes, and particularly to modify their selectivity toward reactions with nonpolar reactants (e.g., nonpolar free radicals) in supercritical carbon dioxide near the critical point. Rate constants for free radical addition of the light hydrogen isotope muonium to ethylene, vinylidene fluoride, and vinylidene chloride in supercritical carbon dioxide are compared over a range of pressures and temperatures. Near carbon dioxide's critical point, the addition to ethylene exhibits critical speeding up, while the halogenated analogues display critical slowing. This suggests that supercritical carbon dioxide as a solvent may be used to tune alkene chemistry in near-critical conditions.

Ligand Binding Properties of Two Different Globin Domains and the Native Hemoglobin of Artemia Salina; A Comparison Study

The brine shrimp Artemia expresses three hemoglobins (Hbs) - Hb I, Hb II, Hb III - which show different oxygen-binding characteristics. Genotypically, four globin chains (C1, C2, T1, and T2) are expressed. The proposed model for their quaternary structure is a heterodimer (Hb I: C1C2, Hb II: C1T2 and Hb III: T1T2) of two ring-shaped polymeric globin chains stacked coaxially. Each globin chain, (Mr ∼160.000) consists of a concatenation of nine globin domains (Mr ∼16.000) different in primary structure. In this study, domain 1 (AsHbD1) and domain 5 (AsHbD5) of chain C1 have been cloned, over-expressed and purified. The kinetic properties of the recombinant proteins as well as that of the native Hb (AsHbN) which was purified from the host were analyzed by using laser flash photolysis. The association rate constant (kon) of CO for the AsHbN as well as the recombinant proteins were measured by using the one pseudo-first order condition approach. The association constant value for AsHbD1, AsHbD5 and AsHbN were determined to be 3.32, 15.9 and 1.7 μM−1s−1, respectively. The nanosecond geminate rebinding constant (kgem) for all samples were measured and AsHbD5 showed higher kgem value. The fraction of ligand that does not escape the protein matrix (geminate fraction or Fgem) of domain 1 and domain 5 are very different, which in turn indicates a different heme pocket structure. In addition, the association and dissociation rate constants of O2 were measured by the displacement technique. It was shown that oxygen affinity (KO2) of AsHbD1 (1.34 μM−1) is higher than that of AsHbD5 (0.53 μM−1) whereas the KO2 of AsHbN is 0.36 μM−1. The results confirm different ligand binding properties of the two globin domains of Artemia Hb.

Electrochemical study of carbonyl phosphine β-diketonato rhodium(I) complexes

Cyclic voltammetry of [Rh(RCOCHCOR′)(CO)(PPh 3 )] complexes. The electrochemical oxidation of a series of [Rh(RCOCHCOR′)(CO)(PPh 3 )] complexes studied in acetonitrile, containing 0.100 mol dm −3 tetra- n -butylammonium hexafluorophosphate as supporting electrolyte, shows that Rh(I) is being oxidized in an electrochemically irreversible two-electron transfer process, at peak anodic potentials ranging from E pa (Rh) = 0.29–0.57 V vs. Fc/Fc + . R and R′ groups on the β-diketonato ligand (RCOCHCOR′) which are more electron withdrawing, reduce electron density on the rhodium atom to a larger extent than electron donating groups do. This leads to a higher, more positive, electrochemical oxidation potential, E pa (Rh). Relationships were established between the electrochemical quantity, E pa (Rh), and chemical oxidation, in terms of the second order kinetic oxidative addition rate constant, k 2 , as well as other parameters related to the electronic effect of the R and R′ groups through conjugation on rhodium in [Rh(RCOCHCOR′)(CO)(PPh 3 )]; such as the sum of the group electronegativities (Gordy Scale) of the R and R′ groups ( χ R + χ R′ ), the Hammett meta σ values ( σ R + σ R′ ) and the p K a of the free β-diketone R′COCH 2 COR. E pa can also be predicted by the density functional theory calculated HOMO energy and the two-electron adiabatic ionization potential, IP 2e− , of these [Rh(RCOCHCOR′)(CO)(PPh 3 )] complexes.

Photocatalytic Monofluorination of Benzene by Fluoride via Photoinduced Electron Transfer with 3-Cyano-1-methylquinolinium

The photocatalytic fluorination of benzene occurs under photoirradiation of an oxygen-saturated acetonitrile (MeCN) of the 3-cyano-1-methylquinolinium ion (QuCN(+)) containing benzene and tetraethylammonium fluoride tetrahydrofluoride (TEAF·4HF) with a xenon lamp (500 W) attached to a colored-glass filter (λ < 290 nm) to yield fluorobenzene and hydrogen peroxide. The quantum yield of formation of fluorobenzene was 6%. Nanosecond laser flash photolysis measurements were performed to elucidate the mechanistic details for photocatalytic fluorination. Transient absorption spectra taken after the nanosecond laser excitation at 355 nm of a degassed MeCN solution of QuCN(+) and benzene exhibited absorption bands due to QuCN(•) (λmax = 500 nm) and the benzene dimer radical cation (λmax = 900 nm), which were generated by photoinduced electron transfer from benzene to the singlet excited state of QuCN(+). The decay rate of the transient absorption band due to the benzene dimer radical cation was accelerated by the addition of TEAF·4HF. The observed rate constant increased with increasing concentration of TEAF·4HF. The rate constant of the electrophilic addition of fluoride to the benzene radical cation was determined to be 9.4 × 10(9) M(-1) s(-1). Thus, the photocatalytic reaction is initiated by intermolecular photoinduced electron transfer from benzene to the single excited state of QuCN(+). The benzene radical cation formed by photoinduced electron transfer reacts with the fluoride anion to yield the F-adducted radical. However, QuCN(•) can reduce O2 to O2(•-), and this is followed by the protonation of O2(•-) to afford HO2(•). The hydrogen abstraction of HO2(•) from the F-adduct radical affords fluorobenzene and H2O2 as the final products.

Rate Rules, Branching Ratios, and Pressure Dependence of the HO2 + Olefin Addition Channels

In this work, we present high-pressure rate rules and branching ratios for the addition of HO2 to olefins through the concerted addition channel to form an alkyl peroxy radical (HO2 + olefin → RO2) and through the radical addition channel to form a β-hydroperoxy alkyl radical (HO2 + olefin → β-QOOH). These rate rules were developed by calculating rate constants for a series of addition reactions involving olefins with varying degrees of branching. The individual rate expressions were determined from electronic structure calculations performed at the CBS-QB3 level of theory combined with TST calculations. The calculated rate constants were found to be in good agreement with those reported in the literature. Next, we calculated apparent pressure- and temperature-dependent rate constants for HO2 addition to the terminal site of 1-butene using an energy-grained master equation (ME) approach and QRRK calculations with a modified strong collision (MSC) approximation. The two methods gave similar results for both reaction classes. We found that, for the radical addition reaction, the high-pressure limit for the stabilization channel is not reached until unusually high pressures (>1000 atm). Instead, this reaction leads to the direct formation of an oxirane + OH. In general, the results for the major channels are in reasonable agreement with prior theoretical and experimental data. Finally, to explicitly examine the effect of pressure, we compared concentration-time profiles for the reactions of HO2 plus butene in air that were obtained using both high-pressure and pressure-dependent mechanisms at 10 and 100 atm. These simulations showed that, contrary to general expectations, the manifestation of pressure falloff effects in kinetic modeling studies might be more prevalent at increasing pressures. This behavior is attributed to the reaction of β-QOOH with O2, the rate of which increases with increasing pressure of air. This bimolecular reaction competes with the unimolecular reactions of β-QOOH under conditions where falloff effects are important for that channel.

Experimental and modeling study on the pyrolysis and oxidation of n-decane and n-dodecane

High pressure n-decane and n-dodecane shock tube experiments were conducted to assist in the development of a Jet A surrogate kinetic model. Jet A is a kerosene based jet fuel composed of hundreds of hydrocarbons consisting of paraffins, olefins, aromatics and naphthenes. In the formulation of the surrogate mixture, n-decane or n-dodecane represent the normal paraffin class of hydrocarbons present in aviation fuels like Jet A. The experimental work on both n-alkanes was performed in a heated high pressure single pulse shock tube. The mole fractions of the stable species were determined using gas chromatography and mass spectroscopy. Experimental data on both n-decane and n-dodecane oxidation and pyrolysis were obtained for temperatures from 867 to 1739K, pressures from 19 to 74atm, reaction times from 1.15 to 3.47ms, and equivalence ratios from 0.46 to 2.05, and ∞. Both n-decane and n-dodecane oxidation showed that the fuel decays through thermally driven oxygen free decomposition at the conditions studied. This observation prompted an experimental and modeling study of n-decane and n-dodecane pyrolysis using a recently submitted revised n-decane/iso-octane/toluene surrogate model. The surrogate model was extended to n-dodecane in order to facilitate the study of the species and the 1-olefin species quantified during the pyrolysis of n-dodecane and n-decane were revised with additional reactions and reaction rate constants modified with rate constants taken from literature. When compared against a recently published generalized n-alkane model and the original and revised surrogate models, the revised (based on our experimental work) and extended surrogate model showed improvements in predicting 1-olefin species profiles from pyrolytic and oxidative n-decane and n-dodecane experiments. The revised and extended model when compared to the published generalized n-alkane and surrogate models also showed improvements in predicting species profiles from flow reactor n-decane oxidation experiments, but similarly predicted n-decane and n-dodecane ignition delay times.

The decomposition of 2-pentyl and 3-pentyl radicals

The isomerization and decomposition reactions of 2-pentyl and 3-pentyl radicals have been studied in a single-pulse shock tube over a temperature range of 973–1121K and pressures of 120–800kPa. The results represent the first direct study of the alkene product branching ratio resulting from the kinetics of the competition between isomerization and beta C–C bond scission for a secondary straight-chain alkyl radical at high temperatures. Such species are representative of intermediates important in the combustion of typical hydrocarbon fuels. In the present work, a small quantity of precursor (∼45μL/L) is used to thermally generate H atoms in the presence of excess (E)-2-pentene, leading to the radicals of interest via addition of H to the double bond. Decomposition of the chemically activated pentyl radicals results in the stable olefin products ethene, propene, and 1-butene, which are detected in postshock gas chromatographic analyses utilizing flame-ionization and mass-spectrometric detection. It is shown that the olefin product ratios can be related to the isomerization and decomposition reactions of the 2-pentyl and 3-pentyl radicals and the results are consistent with the existence of distinct non-overlapping cracking patterns for the two radicals. The data are compared with predictions made on the basis of a model developed from experiments on the decomposition of thermal (i.e. not chemically activated) 1-pentyl radicals. Good agreement is observed. In conjunction with an RRKM/Master Equation analysis, the results for 2-pentyl and 3-pentyl radicals are projected over a wide range of temperatures. In addition, the rate constants for addition of H atoms to the alternate double bond positions of (E)-2-pentene are derived relative to a standard reaction and absolute rate constants for these processes are reported.

Prediction of chemical and electrochemical oxidation potentials of β-diketonatobis(triphenylphosphite)rhodium(I) complexes: A DFT study

The density functional theory calculated energies of the highest molecular orbital of the [Rh(β-diketonato)(P(OX)3)2] complexes (X=H, CH3, Ph) and calculated activation energies of the oxidative addition reaction [Rh(β-diketonato)(P(OH)3)2]+CH3I relate to the electrochemical oxidation potential of rhodium(I) to rhodium(III) in [Rh(β-diketonato)(P(OPh)3)2]. They also relate to the experimental second order oxidative addition rate constant of the reaction [Rh(β-diketonato)(P(OPh)3)2]+CH3I. The results are in close agreement with the electron-donating and -withdrawing properties of the side groups R and R′ on the β-diketonato ligand (RCOCHCOR′)− as described by the Gordy scale group electronegativities, Hammett meta substituent constants, Lever electronic parameters and the pKa of the free β-diketone.

Radical kinetics in sub- and supercritical carbon dioxide: thermodynamic rate tuning

We report rate constants for muonium addition to 1,1-difluoroethylene (vinylidene fluoride) in CO2 at 290-530 K, 40-360 bar, and 0.05-0.90 g cm(-3). Rate constants are mapped against their thermodynamic conditions, demonstrating the kinetic tuning ability of the solvent. The reaction exhibits critical slowing near conditions of maximum solvent isothermal compressibility, where activation volumes of unprecedentedly large magnitudes on the order of ±10(6) cm(3) mol(-1) are observed. Such values are suggestive of pressure being a significant parameter for tuning fluorolkene reactivity.

Infrared Study of the Stability and Folding Kinetics of a Series of β-Hairpin Peptides with a Common NPDG Turn

The thermal stability and folding kinetics of a series of 15-residue β-hairpins with a common Type I [3:5] NPDG turn were studied using Fourier transform infrared spectroscopy (FTIR) and laser-induced temperature jump (T-jump) with infrared detection, respectively. Mutations at positions 3, 5, or 13 in the peptide sequence SEXYXNPDGTWTXTE, where X represents the position of mutation, were performed to study the roles of hydrophobic interactions in determining the thermodynamic and kinetic properties of β-hairpin folding. The thermal stability studies show a broad thermal folding/unfolding transition for all the peptides. T-jump studies indicate that these β-hairpin peptides fold in less than 2 μs. In addition, both folding and unfolding rate constants decrease with increasing strength of hydrophobic interactions. Kinetically, the hydrophobic interactions have more significant influence on the unfolding rate than the folding rate. Φ-value analysis indicates that the hydrophobic interactions between the side chains are mainly formed at the latter part of the transition-state region during the folding process. In summary, the results suggest that the formation of the native structure of these β-hairpins depends on the correct topology of the hydrophobic cluster. Besides the formation of the turn region as a key process for folding as suggested by previous studies, a hydrophobic collapse process may also play a crucial role during β-hairpin folding.

The Growth of Sickle Hemoglobin Polymers

The measurement of polymer growth is an essential element in characterization of assembly. We have developed a precise method of measuring the growth of sickle hemoglobin polymers by observing the time required for polymers to traverse a photolytically produced channel between a region in which polymers are created and a detection region. The presence of the polymer is functionally detected by observing its ability to create new polymers through the well-established process of heterogeneous nucleation. Using this method, we have determined the rate constants for monomer addition to and release from polymer ends, as well as their temperature dependences. At 25°C we find k+ = 84 ± 2 mM−1 s−1 and k− = 790 ± 80 molecules/s from each end. These numbers are in accord with differential interference contrast measurements, and their ratio gives a solubility measured on individual fibers. The single-fiber solubility agrees with that measured in sedimentation experiments. The concentration dependence of the monomer addition rate is consistent with monomer addition, but not oligomer addition, to growing polymers. The concentration dependence suggests the presence of an activation enthalpy barrier, and the rate of monomer addition is not diffusion-limited. Analysis of the temperature dependence of the monomer addition rate reveals an apparent activation energy of 9.1 ± 0.6 kcal/mol.

Tertiary alkoxyl radicals from 3-alkoxythiazole-2(3 H)-thiones

This study deals with the synthesis of tert- O-alkyl thiohydroxamates and their use as tert-alkoxyl radical precursors. tert-Alkoxyl radicals were applied in mechanistic studies to determine rate constants of (i) p-chlorocumyloxyl radical addition to bicyclo[2.2.1]heptene ( k=1×10 7 M −1 s −1), (ii) 2-phenylhex-5-en-2-oxyl radical 5- exo- trig-cyclization ( k cis=3×10 9 s −1, k trans=1×10 9 s −1), and (iii) 2-methyl-5-phenylpent-2-oxyl to 2-hydroxy-2-methyl-5-phenylpent-5-yl radical isomerization (1,5-H-atom shift; k=0.4–1.5×10 8 s −1). The reactions pose key steps in synthesis of 2,2,5-substituted tetrahydrofurans and 2-bromo-3-alkoxybicyclo[2.2.1]heptanes. Stereoselectivity in 5- exo- trig cyclization (2,5-cis) and intermolecular addition ( exo/endo>99:1), originates from torsional strain in transition structures of alkoxyl radical reactions.

Electronic Effects in the Oxidative Addition of Iodomethane with Mixed-Aryl β-Diketiminate Chromium Complexes

The CrII complexes CpCr[DppNC(Me)CHC(Me)NC6H4Y] (1; Dpp = 2,6-(Me2CH)2C6H3) were used to prepare the corresponding CrIII iodo (2) and methyl (3) mixed-aryl β-diketiminate compounds with Y = OMe (a), CH3 (b), H (c), CF3 (d). Oxidation of the CrII precursors with iodine gave CpCr[DppNC(Me)CHC(Me)NC6H4Y](I) (2a−d). The CrIII methyl compounds 3a−d were prepared by reaction of the CrII complexes with iodomethane followed by MeMgI. The CrIII chloride complexes 4a−d were synthesized by salt metathesis of isolated CpCrCl2(THF) with the appropriate deprotonated mixed-aryl β-diketiminate. The structures of the paramagnetic complexes 1b,c, 2a,b, 3a−d, and 4a−d were determined by single-crystal X-ray diffraction. The rate constants for the single-electron oxidative addition of iodomethane with 1a−d were determined by monitoring the reaction by UV−vis spectroscopy. The rate constants correlated well with the electronic parameters of the Y substituents (ρ = −0.36). The rate constants for 1a−d were an order of magnitude greater than those previously obtained for the same reaction with CpCr[(DppNCMe)2CH] and related ortho-disubstituted symmetric β-diketiminate complexes.

Kinetic studies of retinol addition radicals

Retinol neutral radicals (RS-retinol˙), generated from the reaction of retinol with 4-pyridylthiyl and 2-pyridylthiyl radicals in argon-saturated methanol, undergo β-elimination, which can be monitored via the slow secondary absorption rise at 380 nm attributed to the rearrangement of the unstable retinol neutral addition radicals to the more stable addition radicals. Rate constants for the β-elimination reactions (k(β)) of 4-PyrS-retinol˙ were measured at different temperatures and the Arrhenius equation for the reaction is described by log (k(β)/s(-1)) = (12.7 ± 0.2) - (54.3 ± 1.3)/θ, where θ = 2.3RT kJ mol(-1). The reactivities of retinol addition radicals (RS-retinol˙), generated from the reaction of retinol with various thiyl radicals, towards oxygen have also been investigated in methanol. In the presence of oxygen, the decay of RS-retinol˙ fits to biexponential kinetics and both observed rate constants for the RS-retinol˙ decay are oxygen-concentration dependent. This suggests that at least two thiyl addition radicals, formed from the reaction of RS˙ with retinol, undergo oxygen addition reactions. In light of the estimated rate constants for oxygen addition to RS-retinol˙ and RS-CAR˙ (CAR: carotenoid), the antioxidant-prooxidant properties of retinol are discussed.

ChemInform Abstract: Photo-Heterolysis and -Homolysis of Substituted Diphenylmethyl Halides, Acetates, and Phenyl Ethers in Acetonitrile: Characterization of Diphenylmethyl Cations and Radicals Generated by 248-nm Laser Flash Photolysis

Para-substituted diphenylmethyl halides, acetates, and ethers RPh(R'Ph)CH-X (R, R' = CF3 to OCH3), upon photolysis with -250-nm light in acetonitrile solutions, undergo homolysis and heterolysis of the C-X bond to give the radicals, RPh(R'Ph)CH' (abbreviated as C), and the cations, RPh(R'Ph)CH+ ((2'). Whereas the quantum yields for homolysis (0.2-0.4) are rather independent of the nature of the substituent on the benzene ring, those for heterolysis increase with increasing electron-donator strength from 50.07 for CF3 to 0.3 for OMe. The cationxadical ratios are also dependent on the nucleofugal properties of X. For the halides, the observed hetero1ysis:homolysis ratios correlate with the pK, values of the conjugate acids HX and not with the electron affinities of X'. In acetonitrile, heterolysis is much less endothermic than homolysis. Homolysis and heterolysis can also be effected indirectly by reaction with triplet acetophenone (produced by 308-nm photolysis). Unless stabilized by one or more MeO, the cations decay predominantly by reaction with acetonitrile to give nitrilium ions. However, since this reaction is reversible (shown for the benzhydryl cation), the nitrilium ion contributes only to an insignificant degree to the formation of the final (cation-derived) products, which result from reaction with trace water (main product, benzhydryl alcohol; minor, benzhydrylacetamide). The rate constants for addition of C+ to CH$N are in the range 3.5 X lo5 to 3.8 X IO7 s-I for the cations with R = R' = Me to R = H, R' = CF3. The rate constants for reaction of C+ with halides (ion recombination) are -2 X 1O1O M-l s-' (diffusion control). The radicals C' disappear by dimerization and disproportionation, for which a complete mass balance has been achieved by product analysis for the case of the benzhydryl system. At laser-pulse powers > IO mJ electronically excited radicals, C, are additionally formed in many cases, via absorption of a light quantum by ground-state C'.

ChemInform Abstract: Photocatalytic Hydrogenation, Decomposition and Isomerization Reactions of Alkenes Over TiO2-Adsorbed Water

Photocatalytic reactions of alkenes over TiO2-adsorbed water have been investigated. The products are hydrogenated molecules (CnH2n+2) formed by the addition of two H atoms to the π bond of the alkene (CnH2n, 2⩽n⩽ 4) and lower alkanes (CH4, Cn – 2H2n – 2 and Cn–1H2n) formed by the cooperative addition of an H atom and an OH radical to the π bond followed by decomposition. The photocatalytic isomerization of butenes by surface OH radicals is also observed. The generalized reaction mechanisms for these photocatalytic reactions have been postulated. The initial rate of formation of the hydrogenation product and the sum of the initial rates of formation of lower alkanes per amount of alkene adsorbed are proportional to kH and (kHkOH)1/2, respectively. Here, kH and kOH are rate constants for addition of H atoms and OH radicals to alkene in the vapour phase. For photocatalytic isomerizations, it is found that the isomerization of (E)-but-2-ene to but-1-ene (trans form) which has the same geometrical form is about twice as effective as that between (Z)-but-2-ene and but-1-ene and that the addition of OH to the C(1) position of but-1-ene prevents the isomerization to but-2-enes.

Correlation of the Rates of Solvolysis of 4-Morpholinecarbonyl Chloride Using the Extended Grunwald-Winstein Equation

O and MeOD) were also determined to exa-mine isotope effects. Additional rate constants were measured to obtain thermodynamic parameters of activation such as enthalpies of activation and entropies of activation which are summarized in Table 2.As shown in Table 1, the first-order rate constants increase in the order TFE-water < acetone-water < ethanol-water < methanol-water. The rate constants also increase as the water content in the mixed solvents increases, indicating that the reaction rate is accelerated by the solvent with higher ionizing power

The Role of Structural Effects on the Reactions of Alkoxyl Radicals with Trialkyl and Triaryl Phosphites. A Time-Resolved Kinetic Study

A time-resolved kinetic study on the reactions of alkoxyl radicals with trialkyl and triaryl phosphites ((RO)(3)P: R = Me, Et, i-Pr, t-Bu; (ArO)(3)P: Ar = C(6)H(5), 2,4-(t-Bu)(2)C(6)H(3)) has been carried out. In the (RO)(3)P series, the alkoxyl radicals (cumyloxyl (CumO(*)) and benzyloxyl (BnO(*))) undergo addition to the phosphorus center with formation of intermediate tetraalkoxyphosphoranyl radicals (R'OP(*)(OR)(3): R = Me, Et, i-Pr, t-Bu; R' = Bn, Cum). The addition rate constants are influenced by steric effects, decreasing on going from R = Me to R = t-Bu and from BnO(*) to CumO(*). Rate constants for beta-scission of the phosphoranyl radicals R'OP(*)(OR)(3) have also been determined, increasing, for a given alkyl group R, in the order R' = tert-butyl < R' = benzyl < R' = cumyl and, for a given R' group, on going from R = Me to R = i-Pr. This behavior has been explained in terms of the relative stability of the radicals formed after beta-scission, suggesting moreover that steric effects play in this case a minor role. CumO(*) reacts with triaryl phosphites (ArO)(3)P to give phenoxyl radicals, with rate constants that are influenced to a limited extent by substitution of the aromatic rings. The radical scavenging ability of these substrates is briefly discussed.

Time‐Resolved Electron Spin Resonance Spectroscopy of Radicals Formed During Free Radical Polymerizations of Alkyl Acrylates

Time-resolved electron spin resonance (TR ESR) spectra allows direct observation of transient radicals (primary propagating radicals) obtained by the addition reaction of a diphenylphosphinoyl radical to acrylates. The addition rate constants (k(2) ) of the diphenylphosphinoyl radical to the acrylates (initiation rate constants) were determined by the monomer concentration dependence of the decay rate of the diphenylphosphinoyl radical. The value of k(2) was 1.9 × 10(7) s(-1) · M(-1) for the case of t-butyl acrylate, while the k(2) values of ethyl, n-butyl, 2-ethylhexyl, and dodecyl acrylates were about 1 × 10(7) s(-1) · M(-1) . A combination of steady state ESR and TR ESR provided information on the kinetics both of initiation and propagation processes in the radical polymerization of acrylates.

A theoretical study of the kinetics of OH radical addition to halogen substituted propenes

The kinetics of the addition of OH radical to propene and a series of halogen substituted propenes have been investigated using DFT, MP2 and CCSD(T) methods. Activation energies based on MP2/cc-pVTZ single point energy calculations on BH&HLYP/cc-pVTZ optimized structures were found to give rate constants in good agreement with experimental values. Using standard transition state theory the rate constants of the OH radical addition to CF 3CCl CH 2 and cis-CF 3CH CHCl were calculated to be 2.39 × 10 −12 and 5.10 × 10 −13 cm 3 molecule −1 s −1, which suggests that the atmospheric lifetimes of CF 3CCl CH 2 and cis-CF 3CH CHCl are approximately 5 and 23 days, respectively.