Ruthenium(III) catalysis in polymerization of vinyl monomers by charge‐transfer mechanism with aminoalcohols and carbontetrachloride: A kinetic study

The kinetics of ruthenium(III) catalyzed polymerization of vinyl monomers (M) (methyl‐, ethyl‐, and butylacrylates) by charge‐transfer mechanism with aminoalcohols (AA) (namely, ethanol‐, diethanol‐, and triethanol amines) and carbontetrachloride in dimethylsulfoxide medium have been studied. The rate of polymerization depends on the [CCl₄]/[AA] ratio and may be represented as and The rate of polymerization of monomers with each aminoalcohol was found to be in the order R_p (methyl‐)> R_p (ethyl‐)> R_p (butylacrylate) while that of each monomer with different aminoalcohols was found to be in the order of R_p tertiary > R_p secondary > R_p primary aminoalcohol. The suitable mechanism for the polymerization process consistent with kinetic data has been proposed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 585–592, 2006     

Gas-phase thermolysis of sulfur compounds. Part III: n-butyl 2-propenyl sulfide

The pyrolysis of n-butyl 2-propenyl sulfide has been investigated in a static system in the initial pressure range of 50–350 torr. The reaction was found to be homogeneous and first order. The rate coefficients are given by the Arrhenius equation between 262 and 293°C. The rate of the reaction remains unchanged in the presence of cyclohexene as radical inhibitor. The main reaction products were propene and a trimer of n-butyl thioaldehyde. The results are interpreted in terms of a molecular mechanism involving a cyclic six-centered transition state. This mechanism is supported by the pyrolysis of 1,1-dideutero-n-butyl 2-propenyl sulfide at 281°C. The kinetic deuterium isotope effect had a value of 2.7 ± 0.2. Nuclear magnetic resonance and mass spectroscopic analysis of the reaction products showed the deuterium to be distributed as expected from the proposed reaction mechanism.     

Rate constants for the reactions of OH radicals and Cl atoms with diethyl sulfide,Di-n-propyl sulfide,and Di-n-butyl sulfide

Rate constants for the reactions of OH radicals and Cl atoms with diethyl sulfide (DES), di-n-propyl sulfide (DPS), and di-n-butyl sulfide (DBS) have been determined at 295 ± 3 K and a total pressure of 1 atm. Hydroxyl radical rate data was obtained using the absolute technique of pulse radiolysis combined with kinetic spectroscopy. The chlorine atom rate constants were measured using a conventional photolytic relative rate method. The rate constant for the reaction of Cl atoms with dimethyl sulfide (DMS) was also determined. The following rate constants were obtained:      

Effect of amines on the ceric ion-initiated polymerization of vinyl monomers. II. Polymerization of acrylonitrile by ceric ion in presence of various substituted amines

The effect of various substituted amines on the polymerization of acrylonitrile initiated by ceric ammonium sulfate has been studied in aqueous solution at 30°C. It was found that the secondary and tertiary amines considerably increased the rate of polymerization, whereas the primary amines seemed to have no effect at all. From the kinetic studies it was found that the overall polymerization rate R_p is independent of ceric ion concentration and can be expressed by the equation: R_p = k₁ [amine] [monomer] + k₂[monomer]², where k₁ and k₂ are constants (involving different rate constants). The accelerating effect of the amines was attributed to a redox reaction between the ceric ion and the amine involving a single electron transfer, the relative activity of the different amines being thus dependent on the relative electron-donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.     

Vinyl polymerization by carbon black V. Solvent effect and the kinetics of the polymerization of N-vinylcarbazole

The polymerization of N-vinylcarbazole has been carried out at 60°C under nitrogen with different grades of carbon black, N220, N110, N330, and N660 as heterogeneous catalysts. The order of efficiency of the catalysts in regard to the polymerization is: N220 > N110 > N660 > N330. Effect of solvent polarity on the polymerization has been studied with acetonitrile, 1,2-dichloroethane, and toluene-nitrobenzene mixtures. Nitrobenzene, with highest polarity, affords the highest rate, which decreases with decreasing nitrobenzene percentage in the solvent mixture. These features suggest the polymerization to be cationic in nature. The relative viscosities of the polymers are low, but tend to increase only slightly with increasing nitrobenzene content. The rate of polymerization can be expressed by the relation A suitable kinetic model has been presented in conformity with the experimental findings.     

Gas phase thermolysis of allyl cyanomethyl amine,diallyl cyanomethyl amine,diethyl cyanomethyl amine,and diethyl propargyl amine

The title amines were pyrolyzed in a stirred-flow reactor at 380–510°C, pressures of 8–15 torr and residence times of 0.3–2.4 s, using toluene as carrier gas. The substrates with an allyl group yielded propene and iminonitriles as reaction products. HCN is formed by decomposition of the iminonitriles. The first-order rate coefficients for propene formation fit the Arrhenius equations

• Allyl cyanomethyl amine:
• Diallyl cyanomethyl amine:

Diethyl cyanomethyl amine gave a 20:1 gas mixture of ehylene and ethane, plus HCN. The liquid product fraction contained mainly N-ethyl methanaldimine. The first-order rate coefficients for ethylene formation followed the Arrhenius equation Diethyl propargyl amine decomposed cleanly into allene and N-ethyl ethanaldimine. The first-order rate coefficients for allene formation fit the Arrhenius equation The results suggest that the above allyl and propargyl amines decompose unimolecularly by mechanisms involving six-center cyclic transition states. For diethyl cyanomethyl amine, a nonchain free radical mechanism is proposed. © 1995 John Wiley & Sons, Inc.     

The reaction of hydrogen atoms with 1-butanethiol and thiolane the role of chemically activated 1-butanethiol

The reaction of 1-butanethiol with hydrogen atoms has been studied at temperatures of 295° and 576° K under the pressure of 660 Pa, using a conventional discharge-flow apparatus. The reaction products (besides hydrogen sulfide and methane) under the low conversion range (～10%) consisted mainly of n-butane, 1-butene, and propylene-propane, with the relative yields of 70, 25, and 5% at 295° K and 25, 50, and 10% at 576°K. Analysis of kinetic equations by numerical integration indicates that the following initial steps are consistent with the experimental results: where the following expressions have been derived for k₁ and k₂: The subsequent reaction of the butylthio radical with hydrogen atoms leads to the chemically activated 1-butanethiol which either stabilizes to 1-butanethiol or decomposes to 1-butene and hydrogen sulfide, depending on the experimental conditions. A similar analysis of the data on the thiolane-H system has yielded the following rate parameters for the initial step to form the 4-mercapto-1-butyl radical: .     

The activation of amines of various structures in synergistic mixtures with quinones during the retardation of polymerization of methyl methacrylate

The retardation of the radical polymerization of methyl methacrylate (MMA) mixed with quinones (Q) is accompanied by activation of amines of various structures (InH). In the absence of quinones, primary amines (-naphthylamine), secondary amines (diphenylamine,N-phenyl--naphthylamine, dimethyl-bis-p-(phenylaminophenoxy)silane,N,N'-diphenyl-P-phenylenediamine, andN-phenyl-p-aminophenol), and tertiary amines (N,N,N',N'- tetramethylethylenediamine andN,N,N',N'-tetramethyl-p-phenylenediamine) exert no effect on the process. In the presence of 2,3,5,6-tetrachloroquinone orp-benzoquinone, amines inhibit polymerization (synergism). The consumption of amines is due to the abstraction of mobile H-atoms from their molecules. The retatdation by tertiary amines occurs only in the case when a mobile H atom is present at the-C atom of the amine; a mixture containingN,N,N',N'-tetraphenyl-p-phenylenediamine is ineffective. Analysis of various kinetic schemes shows that the activation of amine and its participation in the reaction with growing MMA radicals may occur either through the formation of active inhibitory species incorporated in the donor-acceptor complex, [InH · Q], or by inhibitory radicals, In^.and QH^., generated by the transfer of an H-atom from InH to Q.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 673–678, April, 1995.     

Gas phase thermolysis of benzyl t-butyl sulfide,phenyl t-butyl sulfide,and phenyl t-butyl ether

The pyrolysis kinetics of the title compounds has been studied in a stirred-flow reactor over the temperature range 440–530°C and pressures between 5 and 14 torr. Benzyl t-butyl sulfide and phenyl t-butyl ether formed isobutene as product in over 98% yield, together with the corresponding benzyl thiol and phenol. The benzyl thiol decomposes to a large extent into hydrogen sulfide and bibenzyl. In the pyrolysis of phenyl t-butyl sulfide, the hydrocarbon products consisted of 80 ±5% isobutene plus 20% isobutane, while the sulfur containing products were thiophenol and diphenyl disulfide. Order one kinetics was observed for the consumption of the reactants. The first order rate coefficients, based on isobutene production, followed the Arrhenius equations: Benzyl t-butyl sulfide: Phenyl t-butyl sulfide: Phenyl t-butyl ether: For benzyl t-butyl sulfide and phenyl t-butyl ether, the results suggest a unimolecular mechanism involving polar four center cyclic transition states. For phenyl t-butyl sulfide, the t-butyl-sulfur single bond fission mechanism is a parallel, less important process than the complex fission one.     

Supported (nBuCp)2ZrCl2 Catalysts: Effects of Selected Lewis Acid Organotin Silica Surface Modifiers on Ethylene Polymerization

This study investigated the effects of several organotin silica surface modifiers on the ethylene polymerization performance of (ⁿBuCp)₂ZrCl₂‐based supported catalysts in which MAO and metallocene were sequentially loaded. Each organotin compound acted as a spacer, increasing the catalyst activity. However, the catalyst activity and of the resulting polyethylenes varied as follows: Activity and fractional Sn⁺ charge: ⁿBuSn(OH)₂Cl > MeSnCl₃ > ⁿBuSnCl₃ > Reference catalyst; and, : Reference catalyst > ⁿBuSnCl₃ > MeSnCl₃ > ⁿBuSn(OH)₂Cl. The above catalyst activity rating was explained considering the influence of the Lewis acidity, that is, the fractional Sn⁺ charge of the organotin modifiers on the generation, concentration, and electron density at the active [(ⁿBuCp)₂ZrMe]⁺ cation. All the catalysts showed fairly stable kinetic profiles and produced narrow molecular weight distribution resins; 2.8 ≤ PDI ≤ 3.

     

Kinetics and mechanism of the amine exchange reactions of 2-aminopyridine derived Schiff-base ligands and their copper(II) complexes

The kinetics and product analyses of the amine exchange reactions of two 2-aminopyridine derived Schiff-base ligands and their monomeric bischelate and dimeric copper(II) complexes have been studied. The Schiff-base ligands investigated underwent amine exchange reactions with n-butyl, cyclohexyl, t-butyl amines. The coordination of the Schiff-base ligands to copper(II) rendered the amine exchange reactions slower. With n-butyl and cyclohexyl amines, parallel first- and second-order terms on their concentrations are observed for the amine exchange reactions of copper(II) bischelates and dimer. The kinetic data favor a mechanism involving a rate-limiting elimination of 2-aminopyridine from a diaminoacetal intermediate in preference to a scheme in which a dissociation of the complexes into free ligands and Cu(II) may precede the amine exchange. The steric factors influence the amine exchange reactions of Cu(II) bischelates with the bulkier amines reacting slower as given by the order t-butylamine (3.3 ± 0.3 × 10^?3 dm³/mol·s) < cyclohexylamine (0.2 ± 0.03 dm³/mol·s) < n-butylamine (2.2 ± 0.2 dm³/mol·s). The bulkiness of the t-butyl group and the constraints imposed by the changes in the coordination geometry of Cu(II) on amine exchange not only render the reactions of Cu(II) bischelates slower but also make the formation of the mixed adduct ([N-(5-methyl)-2-pyridyl salicylaldimine][N-t-butyl salicylaldimine] Cu(II)) more favored.     

Studies on some radical transfer reactions by entrapping the radicals as polymer end groups. I. Reaction of hydroxyl radicals with amines

The reaction of OH radicals with a number of amines has been studied by entrapping the resultant radicals as polymer end groups which have been detected and estimated by the sensitive dye partition technique. Expressions have been developed relating the average amounts of end groups per polymer molecule to the rate constant of the radical transfer reaction, the rate constants determined for reaction with n-butyl, n-hexyl, and n-octyl amine being 1.00 × 10¹⁰, 1.31 × 10¹⁰, and 1.46 × 10¹⁰ mol^?1 L s^?1, respectively, at 25°C. The order of reactivity for amines of different classes has been found to be as primary < secondary > tertiary, the rate constants for reaction with n-butyl, dibutyl, and tributyl amine being 1.00 × 10¹⁰, 1.81 × 10¹⁰, and 1.67 × 10¹⁰ mol^?1 L s^?1, respectively, at 25°C. The change in the reactivity of the amine with chain length and amine class has been explained by activation and deactivation of the CH₂ group from which H abstraction by OH radicals occurs, respectively, by the alkyl group and by the protonated amino nitrogen under the acidic condition of the medium. Between pH 1.00 and 2.17, the rate of the reaction with n-butyl amine remains practically unchanged, but from pH 2.20 to 2.72 the rate constant increases with increasing pH, indicating that deprotonation of the positively charged nitrogen starts at about pH 2.20. The method is simple and accurate and can be applied to detect and estimate very reactive radicals.     

Gas-phase thermolysis of sulfur compounds. Part IV. n-propyl allyl sulfide

The pyrolysis of n-propyl allyl sulfide has been studied in static and stirred-flow systems at temperatures between 270 and 400°C. Propene and 2,4,6-triethyl-1,3,5-trithiane were the only reaction products. The order of the reaction was 0.99 ± 0.05 at 377°C. The first-order rate coefficients followed the Arrhenius equation The rate coefficients and the product distribution remained unchanged when cyclohexene was used as carrier gas. A molecular mechanism involving a six-centered cyclic transition state is proposed to explain the present results. This mechanism is further supported by the pyrolysis of 4-thia-5-dideutero-1-heptene at 377°C, where only 3-deuteropropene is formed. The kinetic deuterium isotope effect had a value of 2.6 ± 0.3 at this temperature. The results are compared with those obtained in the pyrolysis of n-butyl allyl sulfide previously reported.     

Gas-phase reaction of n-butyl acetate with the hydroxyl radical under simulated tropospheric conditions: Relative rate constant and product study

The gas-phase reaction of n-butyl acetate with hydroxyl radicals has been studied in an environmental smog chamber at 298 K atmospheric pressure, and simulated tropospheric concentrations. The rate constant for this reaction has been determined by a relative method and the experimental result, relative to n-octane used as reference compound, is This value appears to be about 25% higher than absolute rate constants found in the literature, but agrees very well with the other relative determination. Two reaction products have been identified and their production yield has been estimated, each accounting for about (15 ± 5)% of the overall OH reaction processes. The two observed products are \centerline{ 2--oxobutil acetate ($\rm CH_3$--C0--0--$\rm CH_2$--CO--$\rm CH_2$--$\rm CH_3$)} and \centerline{ 2--oxobutil acetate ($\rm CH_3$--C0--0--$\rm CH_2$--$\rm CH_2$--CO--$\rm CH_3$)} The accuracy of the relative rate constant obtained is examined considering the evolution of the reactivity of the alkoxy end of the esters. Formation mechanisms for the two observed products are proposed and the likely other degradation channels are discussed. © 1996 John Wiley & Sons, Inc.     

A new microwave dielectric method for studying photoinitiated chain radical polymerization processes

Measurements of both real and imaginary parts of the dielectric constant at a fixed microwave frequency have been performed on n-butyl acrylate/poly(n-butyl acrylate) mixtures. The dielectric constant of the mixtures has been compared with that of neat n-butyl acrylate during UV photoinitiated polymerization. The values of the imaginary part of the dielectric constant thus obtained have allowed determination of the instantaneous monomer concentration and verified the kinetic equation for the photoinitiated polymerization process. The limits of validity of the method as well as its capability of providing detailed kinetic information are also discussed.     

Polymerization of methyl methacrylate by charge-transfer mechanism with aliphatic primary amines and carbon tetrachloride

Polymerization of methyl methacrylate (MMA) with aliphatic primary amines and carbon tetrachloride has been investigated in th dimethylsulfoxide medium by employing a dilatometric technique at 60°C. The rate of polymerization (R_p) has been evaluated under the conditions, [CCl₄]/[amine] < 1 and > 1. The kinetic data indicate possible participation of the charge transfer complexes formed between the amine + CCl₄ and the amine + MMA in the polymerization of MMA. In the absence of CCl₄ or amine, no polymerization of MMA was observed under the present experimental conditions. The polymerization of MMA was inhibited by hydroquinone, indicating a free radical initiation. The energy of activation varied from 32 to 58 kJ mol^?1.     

Kinetic analysis based on the excluded-volume effect for radical polymerization

When the potential of average force based on the excluded volume affects the relative motions of the polymer radicals, the specific rate for bimolecular reaction between them can be approximated as k_t = const. (ns)^?a, where a = 0.153(2b ? 1), b being a constant in the Mark-Houwink equation, and n and s being degrees of polymerization. Introduction of such a rate into kinetic equation yields a relative molecular weight distribution: G(n) = (n/m)^2–2a exp {ph(m^1–a ? n^1–a)}, where m = (2/ph)^1/(1–a) is a degree of polymerization for the maximum in G(n) and ph is a parameter denoting kinetic character. Further, the relationship between polymerization rate R_p, monomer concentration [M], and initiator concentration [ε] is found to be: where σ is a parameter denoting primary radical termination and η and η? are viscosities for an arbitrary solvent and ?-solvent, respectively. These relationships are sufficiently applicable to the data obtained in the polymerizations of styrene and methyl methacrylate.     

Gas-phase thermolysis of allyl propargyl amine,allyl cyanomethyl propargyl amine,allyl propargyl 2-thiapropyl amine,and allyl methanesulfonyl propargyl amine

The title amines have been pyrolyzed in a stirred-flow reactor, at temperatures of 360–500°C, pressures of 7–16 torr, and residence times of 0.5–2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7–1.6. The amines with CH₂CN and SO₂CH₃ substituents also formed HCN and SO₂. These appear to arise from complex free radical decomposition of the imine product. The first-order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine: Allyl cyanomethyl propargyl amine: Allyl propargyl 2-thiapropyl amine: Allyl methanesulfonyl propargyl amine: Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.     

Cyclic acetal-photosensitized polymerization. I. Photopolymerization of styrene in the presence of 1,3-dioxolanes

Styrene(St) was polymerized in benzene solution in the presence of substituted 1,3-dioxolane(DO) compounds by means of photoirradiation of the system at 40°C. The subtraction of the square of the polymerization rate in the absence of DO compounds (R_pab) from the square of the rate in the presence of DO compounds (R_ppr) was found to follow the equation: The effect of substituents in the 2-position on the polymerization rate increased in the order of methyl < hydrogen < ethyl < n-propyl < phenyl, as shown by the rate constant k_d′ of decomposition of DO compounds.     

Effect of pressure on the radiation-induced polymerization of ethylene in tert-butyl alcohol

The effects of pressure of the radiation-induced polymerization of ethylene in tert-butyl alcohol were studied. The reaction was carried out by use of a reactor with a capacity of 100 ml under the following conditions; pressure, 60–400 kg/cm²; temperature, 24 ± 3°C; dose rate, 2.0 × 10⁴?1.6 × 10⁵ rad/hr; amount of medium (tert-butyl alcohol containing 5 vol-% water), 70 ml. The results of polymerization were analyzed by a kinetical treatment based on a reaction mechanism with both first- and second-order terminations for the concentration of propagating, radical. On the basis of the kinetical treatment the rate constants of each elementary reaction at several pressures were determined, and the activation volumes of elementary reactions were obtained and are discussed in connection with the reaction mechanism. Consequently, the rate constants of propagation, first-order termination, and second-order termination at pressure p and at 24°C were expressed by,