The mechanisms of retardation and inhibition in radical polymerizations. Part 1.—The retardation by p-benzoquinone of the polymerization of methyl methacrylate

Bevington, J. C.; Ghanem, N.A.; Melville, H. W.

doi:10.1039/tf9555100946

Cited by 31 publications

(9 citation statements)

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“…The benzene solvent was purified by fractionation of A.R. material with 1% absolute ethanol to remove suspended water as the ternary azeotrope, 29 and the polymer solutions were clarified by filtration through No. 1 sintered glass.…”

Section: Viscosity Measurementsmentioning

confidence: 99%

The mechanisms of radiation‐induced changes in vinyl polymers

Todd

1960

J. Polym. Sci.

100

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Methyl methacrylate, labeled with 14C on the ester methyl group, was prepared by the ester interchange method of Blackley and Mel~il1e.I~ A small highly active sample of 14C-labeled methanol, containing 500 pc., was obtained from the Radio-Chemical Centre, Amersham, in a Pyrex "breakseal" tube. This was diluted to 10 ml. (sufficient for the preparation of both active l4C-methyl methacrylate and l4C-methyl acrylate) with dry, degassed methanol on a high vacuum line. Here, 5.2 ml. of this 14Cmethanol was used to prepare 45 ml. of l4C-methyl methacrylate, which would have a specific activity of about 4.8 pc./g. if equilibrium was assumed to have been reached in the ester-interchange reaction.Polymerization of the pure monomers was carried out in Pyrex dilatometers of about 40 ml. capacity after thorough degassing under high vacuum, and the rates were followed to ensure that they were normal. Suit- Activity MeasurementsRadioactive assay of 14Glabeled polymers was carried out by Dr. J. C . Bevington by the gas-counting technique development by Bevington et al. 3 1Repeat activity measurements were made by dilution of the carbon dioxide from duplicate combustions of each polymer sample.

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Section: Viscosity Measurementsmentioning

confidence: 99%

The mechanisms of radiation‐induced changes in vinyl polymers

Todd

1960

J. Polym. Sci.

100

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“…Wako reagent grade CH 3 CN and ultrapure water were used for LC/MS analyses. To determine the structures of the inhibitory reaction products by 1 H-NMR and 13 C-NMR, purified reaction products were isolated through preparative thin-layer chromatography (PTLC) and analyzed by a JEOL ECX-400 spectrometer in CDCl 3 for routine measurements and 2D analyses using 1 H-detected multiple quantum coherence (HMQC) and 1 H-detected multi-bond heteronuclear multiple quantum coherence (HMBC) pulse sequences to determine the structures of inhibition products unequivocally. The 1 H-NMR and 13 C-NMR spectra of the inhibition reaction products were compiled in the Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

“…This is a means to check the actual inhibition products generated by the usual termination process in polymer synthesis using NQ inhibitors. We have used this model approach because it is very difficult to derive trustworthy structural information using standard solution nuclear magnetic resonance (NMR) measurements ( 13 C-NMR and 1 H-NMR) and solid-state cross-polarization and magic angle spinning (CP/MAS) 13 C-NMR on real polymerization systems. In particular, the smaller NMR peaks corresponding to the inhibitor (NQ) are buried in the many peaks arising from the poly(MMA) part of the reaction products after the actual bulk polymerization process.…”

Section: Introductionmentioning

confidence: 99%

“…Two major inhibition reaction products are reported— quinones and ethers —formed either at the carbon atom in the quinone ring or at the carbonyl oxygen atom, respectively, as shown in Scheme . In the case of 1,4‐benzoquinone (BQ), the radicals are trapped at the carbonyl oxygen to form an ether, whereas NQ is reported to quench propagating radicals at the carbon, thus forming quinone products . So how can we predict, rationally, the structural and electronic factors determining the capture sites of the propagating radicals depending on the inhibitors?…”

Section: Introductionmentioning

confidence: 99%

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Inhibitory regulation mechanism of naphthoquinone and its derivatives in radical polymerization

Ichihara

Kawamura

Sakakibara

et al. 2019

J of Physical Organic Chem

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The inhibitory regulation mechanism towards the methyl 2‐methylpropionate radical (a model of the poly(methyl methacrylate) [MMA] propagation radical) by naphthoquinone derivatives in radical polymerization in an aerobic or anaerobic atmosphere has been studied experimentally by liquid chromatography, mass spectrometry, and nuclear magnetic resonance (NMR) measurements of the isolated reaction products, which were purified by preparative thin‐layer chromatography. In addition, we have carried out a theoretical analysis (DFT B3LYP/6‐311+G**) of the frontier orbital interactions and reaction Gibbs free energies (ΔG) for the formation of the relevant reaction products and intermediates and activation free energies (ΔG#) and frontier electron densities (fA(R)) of the radical reactions. Consequently, the reaction mechanism where quinone products are formed by the attack of propagation radicals at the C2 carbon next to the carbonyl group in naphthoquinone was rationalized.

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“…At a reaction time of 0.5 h, the yield is 58 mol% in the absence of p-benzoquinone, whereas it is only 4.7mol% at a mol ratio of p-benzoquinone to carbon tetrachloride of 0.1. paraBenzoquinone is a strong radical-capturing agent. 16 The decrease in the yield of terephthalic acid by the addition of p-benzoquinone should not be associated with the formation of fJ-CyD-p-benzoquinone complex, because the formation constant of fJ-CyD-p-benzoquinone complex is much smaller than that of fJ-CyD-benzoic acid complex as described later.…”

Section: Carboxylation Of Benzoic Acidmentioning

confidence: 99%

Selective Carboxylation of Benzoic Acid Using Cyclodextrin as Mediator

Shiraishi

Kojima

Tomita

et al. 1996

Polym J

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ABSTRACT:The selective synthesis ofterephthalic acid from benzoic acid with carbon tetrachloride, copper powder, and aqueous alkali was achieved by the usc of P-cyclodextrin (jJ-CyD) as a mediator at 60°C under nitrogen of atmospheric pressure, producing terephthalic acid in 74 mol% yield with 100% selectivity. When iX-CyD or y-CyD was used instead of {J-CyD, the reaction hardly proceeded. The addition of p-benzoquinone to the reaction mixture decreased the yield ofterephthalic acid remarkably. An oxygen atmosphere also suppressed the reaction appreciably. Thus, the active species formed from carbon tetrachloride and copper powder in the reaction mixture is proposed to be trichloromethyl radical. The conformations of CyDbenzoate inclusion complexes in aqueous alkaline solution were determined by the nuclear magnetic resonance spectroscopy using 1 H homonuclear Overhauser enhancement on the rotating frame. The benzoate anion was axially included in the cavity of P-CyD with orientation such that the carboxylate group was at the primary hydroxyl side of P-CyD. The essential factor of the carboxylation by the use of P-CyD was the inclusion complex formation of P-CyD with benzoate anion and fJ-CyD with carbon tetrachloride in the reaction mixture. The very high selectivity was ascribed to the conformation of the P-CyD-benzoate inclusion complex.

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The mechanisms of retardation and inhibition in radical polymerizations. Part 1.—The retardation by p-benzoquinone of the polymerization of methyl methacrylate

Cited by 31 publications

References 0 publications

The mechanisms of radiation‐induced changes in vinyl polymers

The mechanisms of radiation‐induced changes in vinyl polymers

Inhibitory regulation mechanism of naphthoquinone and its derivatives in radical polymerization

Selective Carboxylation of Benzoic Acid Using Cyclodextrin as Mediator

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