312. The kinetics of acid-catalysed cyclisation of distyrene and di-(α-methylstyrene)

Barton, Jerry M.; Pepper, D. C.

doi:10.1039/jr9640001573

Cited by 17 publications

(12 citation statements)

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“…Vairon's group expressly selected TMS for their investigations for several reasons: with this monomer, side reactions, such as indanyl cyclization or intermolecular Friedel–Crafts alkylation, which normally plague carbocationic St polymerization,49–52 are absent because of the three methyl substituents on the ring; BCl 3 exclusively forms monomeric BCl 4 − counteranions (Fig. 2); and k i ≈ k p can be assumed 9.…”

Section: Carbocationic Polymerization Of Tms: a Case Studymentioning

confidence: 99%

Kinetics and mechanisms in carbocationic polymerization: The quest for true rate constants

Puskás

Chan

McAuley

et al. 2005

J. Polym. Sci. A Polym. Chem.

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This article is a critical analysis of kinetic dataavailable on carbocationic polymerizations. A survey of published propagation rate constant (kp) data revealed several orders of magnitude differences. In this article, an explanation of this apparent discrepancy is offered with a case study involving the carbocationic polymerization of 2,4,6‐trimethylstyrene (TMS). With the polymerization mechanism originally proposed for this system, kp = 1.35 × 104 L mol−1 s−1 was extracted from experimental data with the Predici polyreaction package. The alternative mechanism yielded kp = 1.01 × 107 L mol−1 s−1, close to that predicted by Mayr's Linear Free Energy Relationship (LFER). We propose that true rate constants can only be obtained from direct competition experiments or from kinetic interpretation based on independently proven mechanisms. The second part of this review discusses critical analysis of the temperature and concentration dependence of various living IB systems. Comparison of the temperature dependence in systems initiated with 2‐ chloro‐2,4, 4‐ trimethylpentane (TMPCl)/TiCl4 from various laboratories yielded of ΔH ∼−25 and −34.5 kJ/mol for high and low TMPCl/TiCl4 ratios, respectively. Aromatic (cumyl‐type) initiators show ΔH ∼ −40 kJ/mol, whereas H2O/TiCl4 in the presence of the strong electron‐ pair donor dimethylacetamide gave ΔH = −12 kJ/mol. The significant differences indicate different underlying mechanisms with complex elementary reactions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5394–5413, 2005

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Section: Carbocationic Polymerization Of Tms: a Case Studymentioning

confidence: 99%

Kinetics and mechanisms in carbocationic polymerization: The quest for true rate constants

Puskás

Chan

McAuley

et al. 2005

J. Polym. Sci. A Polym. Chem.

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“…It takes several possible reactions into account: D reversible protonation, reversible dimerization into DD + , and DI formation either by spontaneous cyclization of DD + or by a transfer reaction to a D double bond which was postulated by Barton and Pepper. 4 Longer oligomers were not considered since they were always present in low amounts, 1 and reversible ester formation was not included since such a triflate ester could not be observed. 9 Hydride abstraction from D, which was described in the first part of this series, 1 was considered as negligible and thus was not included in Scheme 3.…”

Section: Resultsmentioning

confidence: 99%

“…Barton and Pepper studied the rate of double bond consumption for reactions of D with sulfuric, chlorosulfonic, and perchloric acids in 1,2-dichloroethane solvent at temperatures higher than 0 °C. With the former two acids, the consumption rate was very fast during the first few percent of conversion but later decreased.…”

Section: Introductionmentioning

confidence: 99%

Stopped-Flow Investigation of Trifluoromethanesulfonic Acid Initiated Cationic Oligomerization of trans-1,3-Diphenyl-1-butene. 2. A Model Kinetic Study of Styrene Cationic Polymerization

et al. 1998

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Study of the reaction of trans-1,3-diphenyl-1-butene (D, the trans ethylenic dimer of styrene) with triflic acid in dichloromethane has been carried out using stopped-flow technique with UV-visible spectroscopic detection. Product characterizations and cation observations have been previously described, and the present work consists of a kinetic study of the reactions which can be considered as model reactions for the behavior of the polystyryl cations in the styrene cationic polymerization, after complete conversion of the monomer. The main observed cationic species were 1,3-diphenyl-1-butylium (D + ) and oligomeric cations (Dn + ); they absorbed at 340 nm and had a transient existence. Absorbance at 340 nm first increased very fast to reach a maximum value within a few seconds, after which the peak slowly decreased. Its persistence time was shortened when either acid concentration or temperature were increased or when the D concentration was decreased. From the analysis of the rate of appearance of the 340 nm peak, kinetics of protonation of D has been studied. Reaction was first order with respect to D and 1.26 order with respect to acid. The absorbance at 340 nm reached a maximum (OD max), the value of which increased when acid and D initial concentrations were increased and when temperature was lowered. Concentration of cations remained always very low as compared to the initial concentrations of reagents. As for the polymerization of styrene initiated with triflic acid, the low amount of propagating cations indicates fast deprotonation either by β-elimination or by indanic cyclization.

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“…Anhydrous perchloric acid was prepared from 7 2 % aqueous solution by dehydra tion with excess H 2S0 4 as described in detail by Barton & Pepper (1964)-I t was stored in the form of stock solutions of ca. 50 m M concentration.…”

Section: Methodsmentioning

confidence: 99%

“…As indicated by the results in table 2, monomer transfer appears to produce polymer with unsaturated (cyclized) end groups. The readiness of styrene derivatives to undergo such acid catalysed cyclization to indanes (Barton & Pepper 1964) thus appears to be the reason for their high susceptibility to monomer transfer.…”

Section: Absolute Rate Constantsmentioning

confidence: 99%

The polymerization of styrene by perchloric acid

Pepper

Reilly

1966

Proc. R. Soc. Lond. A

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The rates and degrees of polymerization of styrene by perhcloric acid have been measured dilatometrically at 25, 0 and –30°C in solution in 1, 2-dichloroethane ( DCE ), carbon tetrachloride and mixtures of these and other solvents. The rates, throughout the conversion are found proportional to the first power of the monomer concentration, and to the initial concentration of perchloric acid. They are unaffected by traces of water, but show a strong solvent effect. In DCE + CCl 4 mixtures the rates correlate simply with the dielectric constant of the mixture; other solvents show specific solvent effects especially nitro compounds which inhibit. The molecular weights are very low (1000 to 6000) and give evidence of two rapid transfer processes, spontaneous and to monomer. The polymer contains both saturated and unsaturated chains, the fraction of the former correlating with the fraction stopped by the monomer transfer process. The catalyst is not consumed. Further doses of monomer are polymerized at virtually the original rate, but are not added to the first formed chains. The polymerization is interpreted as a ‘transfer-dominated’ living polymerization, with a fast initiation and no termination. The overall rate is therefore taken to be that of the propagation step. Rate constants and activation energies for this and for the transfer processes are derived.

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312. The kinetics of acid-catalysed cyclisation of distyrene and di-(α-methylstyrene)

Cited by 17 publications

References 0 publications

Kinetics and mechanisms in carbocationic polymerization: The quest for true rate constants

Kinetics and mechanisms in carbocationic polymerization: The quest for true rate constants

Stopped-Flow Investigation of Trifluoromethanesulfonic Acid Initiated Cationic Oligomerization of trans-1,3-Diphenyl-1-butene. 2. A Model Kinetic Study of Styrene Cationic Polymerization

The polymerization of styrene by perchloric acid

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