Reactions of aryl diazonium salts and arylazo alkyl ethers. 7. Kinetic studies of the decomposition of Z ethers derived from some substituted 2-nitrobenzenediazonium salts

1982 ◽  
Vol 47 (19) ◽  
pp. 3673-3679 ◽  
Author(s):  
Trevor J. Broxton ◽  
Michael J. McLeish
Keyword(s):  
Kinetic Studies ◽  
Diazonium Salts ◽  
Alkyl Ethers

Reactions of aryl diazonium salts and arylazo alkyl ethers. III. Substituent effects in the ionization of anti-arylazo ethyl ethers in ethanol

1978 ◽  
Vol 31 (7) ◽  
pp. 1519 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Substituent Effects ◽  
Parameter Analysis ◽  
Diazonium Salts ◽  
Resonance Effects ◽  
Inductive Effects ◽  
Alkyl Ethers

A dual substituent parameter analysis of substituent effects on the ionization of anti-arylazo ethyl ethers in ethanol shows that the reaction is affected primarily by inductive effects. The reaction is insensitive to resonance effects and an explanation for this behaviour is offered.

Reactions of Aryl Diazonium Salts and Arylazo Alkyl Ethers. IV. Substituent Effects on the Rates of Some Reactions of syn-Arylazo Ethyl Ethers in Ethanol

1979 ◽  
Vol 32 (5) ◽  
pp. 1031 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Substituent Effects ◽  
Diazonium Salts ◽  
Recombination Mechanism ◽  
Alkyl Ethers

Substituent effects on the rates of ionization (kIS), decomposition (kD) and syn-anti interconversion (kp) for a number of syn-arylazo ethyl ethers have been measured. The rates of ionization and syn-anti interconversion correlate well with sigma while the rates of decomposition correlate with σ+. Substituent effects on the ionization of the syn-ethers are compared to those for ionization of the anti-ethers. Substituent effects on the rate of syn-anti interconversion support the proposed ionization-recombination mechanism.

Novel Ether Modifiers for Anionic Polymerization of Isoprene

1998 ◽  
Vol 71 (1) ◽  
pp. 62-69 ◽  
Author(s):  
W. L. Hsu ◽  
A. F. Halasa ◽  
T. T. Wetli
Keyword(s):  
Anionic Polymerization ◽  
Kinetic Studies ◽  
Polymerization Rate ◽  
Skid Resistance ◽  
Large Excess ◽  
Tire Industry ◽  
Rate Difference ◽  
Alkyl Groups ◽  
Alkyl Ethers ◽  
Isoprene Polymerization

Abstract Because of demands on tire skid resistance, polyisoprenes with high 3,4-content are of particular interest to the tire industry due to their inherently better grip properties. Polar bidentate modifiers such as TMEDA and DIGLYME are widely used in organo-lithium catalyzed isoprene polymerization to increase 3,4-content. However, neither modifier is very effective for making high Tg polyisoprenes due to the fact that a retarded polymerization rate was found for the former while a large excess of modifier was needed for the latter. The new modifiers based on the alkyl ethers of tetrahydrofurfuryl alcohol with alkyl groups from one to six carbon atoms were found to be very effective for producing polyisoprenes with high 3,4-contents. Kinetic studies on both TMEDA and the new ether modified isoprene polymerizations were conducted. The results and the plausible explanation of the rate difference for both systems are discussed.

Reactions of aryl diazonium salts and arylazo alkyl ethers. VI. A comparison of the available methods for the measurement of the rate of ionization of (Z)-arylazo alkyl ethers in alcoholic solvents

1982 ◽  
Vol 35 (2) ◽  
pp. 319 ◽  
Author(s):  
TJ Broxton ◽  
MJ Mcleish
Keyword(s):  
Substituent Effects ◽  
Ionization Rate ◽  
New Method ◽  
Diazonium Salts ◽  
Advantages And Disadvantages ◽  
Diazonium Ions ◽  
Alkyl Ethers ◽  
Trapping Agent ◽  
Ionization Rates

Two previously reported methods for the determination of the ionization rate of (Z)-arylazo alkyl ethers by using x-naphtholate ions as a trapping agent are compared. A new method, which uses thiophenolate ions to trap the free diazonium ions formed in this ionization, is reported. This method is recommended in preference to the earlier methods because it includes a correction for the effect of the ionic strength of the solution on the rate of ionization. Rates measured by the thiophenolate method are consequently lower than those measured by either of the two previous methods. The advantages and disadvantages of the new method are discussed. The magnitude of salt effects and substituent effects on the ionization of (Z)- and (E)-arylazo alkyl ethers are compared.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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