Some Problems Concerning the Mechanism of the Isotactic Polymerization of Methyl Methacrylate Initiated by Organomagnesium Compounds in Toluene Solution—Application of Modified Dilatometer and NMR Methods

Allen, P. E. M.; Mair, C.; Fisher, Mark; Williams, Evan H.

doi:10.1080/00222338208056466

Journal of Macromolecular Science: Part A - Chemistry

1982

DOI: 10.1080/00222338208056466

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Some Problems Concerning the Mechanism of the Isotactic Polymerization of Methyl Methacrylate Initiated by Organomagnesium Compounds in Toluene Solution—Application of Modified Dilatometer and NMR Methods

P. E. M. Allen¹,

C. Mair²,

Mark Fisher³

et al.

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Cited by 11 publications

References 11 publications

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Das Mehrzentrenproblem bei ionischen Polymerisationsprozessen

Erussalimsky¹

1983

Acta Polymerica

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Die gleichzeitige Wirkung verschiedener aktiver Zentren in ionischen Systemen wird sowohl unter dem Aspekt ihrer Besonderheiten als auch hinsichtlich ihres relativen Anteils an experimentellen Gesamteffekten betrachtet. Bildungsweise und konkrete Typen von koexistierenden aktiven Zentren in anionischen, kationischen und durch Übergangsmetallderivate initiierten Polymerisationsprozessen werden diskutiert. An Beispielen der Aggregierung, Dissoziation, Isomerisation, intermolekularen und intramolekularen Komplexbildung werden die Mehrzentreneffekte besprochen.

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Das Mehrzentrenproblem bei ionischen Polymerisationsprozessen

Erussalimsky¹

1983

Acta Polymerica

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An NMR Study of the Dynamics of the Schlenk Equilibrium of 2‐Methylpropylmagnesium Bromide in Tetrahydrofuran

Allen

Hagias

Lincoln

et al. 1982

Ber Bunsenges Phys Chem

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A 90 MHz proton NMR determination of the activation and thermodynamic parameters of the Schlenk equilibrium of 2‐methylpropylmagnesium bromide in tetrahydrofuran is reported. The entropy of activation is consistent with bimolecular reactions of unassociated species proceeding through a transition state resembling a mixed‐bridge dimer. The quantitative data confirm accepted concepts of the solvation states of the species involved. — Association equilibria were explored in order to ensure that they were insignificant under the conditions of the kinetic measurements on the Schlenk equilibria. — The association of di‐2‐methylpropylmagnesium is strongly concentration‐dependent but almost temperature‐independent. The exchange rate is too slow to be measured by NMR methods and much slower than the Schlenk equilibrium. The associates are either cyclic or cluster compounds, or, if linear, have an average degree of polymerization of 10. — The field positions of the resonances of RMgBr and R2Mg reverse at low temperature.

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An NMR Study of the Schlenk Equilibrium of tert‐Butylmagnesium Bromide in Tetrahydrofuran

Allen

Hagias

Mair

et al. 1984

Ber Bunsenges Phys Chem

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P. E. M. Allen et al.: An NMR Study of the Schlenck Equilibrium of tert-Butylmagnesium Bromide in TetrahydrofuranGrignard / Spectroscopy, Nuclear Magnetic Resonance / Thermodynamics A 300 MHz proton NMR determination of the thermodynamic parameters of the Schlenk equilibrium of tert-butylmagnesium bromide in tetrahydrofuran is reported for the temperature range 285 -330 K . In solutions where bromide is in excess over tert-butyl groups other equilibria intervene below 285 K. However when the Grignard stoichiometry prevails concentrations are governed by the Schlenk equilibrium and its determined parameters to at least 260 K. -The Ashby assignments of the 'H resonances (low field: tBuMgBr, high field: tBu,Mg) are confirmed over the temperature range of our measurements but have been found to invert below 200-210 K. Resonances arising from impurities are assigned. -The I3C spectrum is assigned. The CH, resonance of tBu,Mg occurs at a lower field than that of tBuMgBr. The equilibrium parameters determined from the I3C spectra over the temperature range 282-322 K agree with those determined from the 'H spectra though their precision is less.

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Some Problems Concerning the Mechanism of the Isotactic Polymerization of Methyl Methacrylate Initiated by Organomagnesium Compounds in Toluene Solution—Application of Modified Dilatometer and NMR Methods

Cited by 11 publications

References 11 publications

Das Mehrzentrenproblem bei ionischen Polymerisationsprozessen

Das Mehrzentrenproblem bei ionischen Polymerisationsprozessen

An NMR Study of the Dynamics of the Schlenk Equilibrium of 2‐Methylpropylmagnesium Bromide in Tetrahydrofuran

An NMR Study of the Schlenk Equilibrium of tert‐Butylmagnesium Bromide in Tetrahydrofuran

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