scholarly journals How intramolecular coordination bonding (ICB) controls the homolysis of the C–ON bond in alkoxyamines

RSC Advances ◽  
2019 ◽  
Vol 9 (44) ◽  
pp. 25776-25789 ◽  
Author(s):  
Gérard Audran ◽  
Elena Bagryanskaya ◽  
Irina Bagryanskaya ◽  
Mariya Edeleva ◽  
Jean-Patrick Joly ◽  
...  
Keyword(s):  
Rate Constant ◽  
Intramolecular Coordination ◽  
Coordination Bonding ◽  
Essential Parameter ◽  
Bond Homolysis ◽  
Major Alteration

Because the C–ON bond homolysis rate constant kd is an essential parameter of alkoxyamine reactivity, it is especially important to tune kd without a major alteration of the structure of the molecule.

Steric and Polar Effects of the Cyclic Nitroxyl Fragment on the C−ON Bond Homolysis Rate Constant

2005 ◽  
Vol 38 (24) ◽  
pp. 9974-9984 ◽  
Author(s):  
Hanns Fischer ◽  
Andreas Kramer ◽  
Sylvain R. A. Marque ◽  
Peter Nesvadba
Keyword(s):  
Rate Constant ◽  
Bond Homolysis

C–ON bond homolysis of alkoxyamines: when too high polarity is detrimental

2017 ◽  
Vol 15 (29) ◽  
pp. 6167-6176 ◽  
Author(s):  
Paulin Nkolo ◽  
Gérard Audran ◽  
Raphael Bikanga ◽  
Paul Brémond ◽  
Sylvain R. A. Marque ◽  
...  
Keyword(s):  
Rate Constant ◽  
Parabolic Model ◽  
Linear Relationships ◽  
Bond Homolysis ◽  
High Polarity

In this article, previous multi-parameter linear relationships are amended using a parabolic model to describe the effect of EWGs in the alkyl fragment of alkoxyamines on the homolysis rate constant kd.

Long-Range Polar Effect on the C-ON Bond Homolysis in (tert-Butyl[1-(diethylphosphonyl)-2,2-dimethylpropyl]aminoxyl) SG1-Based Alkoxyamines

2004 ◽  
Vol 69 (12) ◽  
pp. 2223-2238 ◽  
Author(s):  
Denis Bertin ◽  
Didier Gigmes ◽  
Sylvain R. A. Marque ◽  
Stephan Milardo ◽  
Jérôme Peri ◽  
...  
Keyword(s):  
Radical Polymerization ◽  
Rate Constant ◽  
Rate Constants ◽  
Bond Cleavage ◽  
Nitroxyl Radicals ◽  
Cleavage Rate ◽  
Factors Influencing ◽  
Alkyl Acrylate ◽  
Bond Homolysis ◽  
Acrylate Monomers

Alkoxyamines and persistent nitroxyl radicals are important regulators of nitroxide-mediated radical polymerization. Because the polymerization times decrease with the increasing rate constant of the homolysis of the C-ON bond between the polymer chain and the nitroxyl moiety, the factors influencing the cleavage rate constant are of considerable interest. Because alkyl acrylate monomers are among the most used in polymerization, we present the measures of the rate constants (kd) of the C-ON bond cleavage for new SG1 based alkoxyamine models containing para-substituted aromatic acrylates (4-XC6H4OC(O)C(Me)H-SG1). It appears that the values of kd increase with the electron-withdrawing properties of the para-substituent groups (4-X) of the ester SG1-based alkoxyamines.

Functional Properties of p-Anisoylated Plasmin-Staphylokinase Complex

1993 ◽  
Vol 70 (02) ◽  
pp. 326-331 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
R A G Smith ◽  
D Collen
Keyword(s):  
Human Plasma ◽  
Rate Constant ◽  
Time Course ◽  
Bolus Injection ◽  
Similar Rate ◽  
Clot Lysis ◽  
Lag Phase ◽  
Plasma Clot ◽  
Rapid Clearance ◽  
Stoichiometric Complex

SummaryThe kinetic and fibrinolytic properties of a reversibly acylated stoichiometric complex between human plasmin and recombinant staphylokinase (plasmin-STAR complex) were evaluated. The acylation rate constant of plasmin-STAR by p-amidinophenyl-p’-anisate-HCI was 52 M-1 s-1 and its deacylation rate constant 1.2 × 10-4 s-1 (t½ of 95 min) which are respectively 50-fold and around 3-fold lower than for the plasmin-streptokinase complex. The acylated complex was stable as evidenced by binding to lysine-Sepharose. However, following an initial short lag phase, the acylated plasmin-STAR complex activated plasminogen at a similar rate as the unblocked complex, whereas the acylated plasmin-streptokinase complex did not activate plasminogen. These findings indicate that STAR, unlike streptokinase, dissociates from its acylated complex with plasmin in the presence of excess plasminogen. In agreement with this hypothesis, the time course of the lysis of a 125I-fibrin labeled plasma clot submerged in citrated human plasma, is similar for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR (50% clot lysis in 2 h requires 12 nM of each agent). The plasma clearances of STAR-related antigen following bolus injection in hamsters were 1.0 to 1.5 ml/min for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR, as a result of short initial half-lives of 2.0 to 2.5 min.The dissociation of the anisoylated plasmin-STAR complex and its consequent rapid clearance suggest that it has no apparent advantages as compared to free STAR for clinical thrombolysis.

Morphological and Photodecomposition Rate Constant Study of PVC Films Doped with Sulfadiazine Tin(IV) Complexes

2020 ◽  
Vol 14 (2) ◽  
pp. 88
Author(s):  
Emad Yousif
Keyword(s):  
Radiation Exposure ◽  
Uv Radiation ◽  
Rate Constant ◽  
Experimental Results

This article focus on the calculation of photodecomposition rate constant of PVC films that containing sulfadiazine tin(IV) complexes 1-3 as photostabilzers during UV radiation exposure. This constant calculated as a method for evaluating the efficiency of sulfadiazine tin(IV) complexes 1-3 when used as a PVC photostabilizers after 300 hours of irradiation. The experimental results showed that sulfadiazine tin(IV) complexes 1-3 have reduced the rate of photodecomposition constant value of PVC films significantly with comparison to PVC (blank).

Dynamic Emergence of Nanostructure and Transport Properties in Perfluorinated Sulfonic Acid Ionomers

2020 ◽  
Author(s):  
Adlai Katzenberg ◽  
Debdyuti Mukherjee ◽  
Peter J. Dudenas ◽  
Yoshiyuki Okamoto ◽  
Ahmet Kusoglu ◽  
...  
Keyword(s):  
Rate Constant ◽  
Sulfonic Acid ◽  
Mass Fraction ◽  
Gas Permeability ◽  
Transport Processes ◽  
Segmental Mobility ◽  
The Matrix ◽  
Swelling Rate ◽  
Ion Conducting ◽  
Perfluorinated Sulfonic Acid

<p>Limitations in fuel cell electrode performance have motivated the development of ion-conducting binders (ionomers) with high gas permeability. Such ionomers have been achieved by copolymerization of perfluorinated sulfonic acid (PFSA) monomers with bulky and asymmetric monomers, leading to a glassy ionomer matrix with chemical and mechanical properties that differ substantially from common PFSA ionomers (e.g., Nafion™). In this study, we use perfluorodioxolane-based ionomers to provide fundamental insights into the role of the matrix chemical structure on the dynamics of structural and transport processes in ion-conducting polymers. Through <i>in-situ</i> water uptake measurements, we demonstrate that ionomer water sorption kinetics depend strongly on the properties and mass fraction of the matrix. As the PFSA mass fraction was increased from 0.26 to 0.57, the Fickian swelling rate constant decreased from 0.8 s<sup>-1</sup> to 0.2 s<sup>-1</sup>, while the relaxation rate constant increased from 3.1×10<sup>-3</sup> s<sup>-1</sup> to 4.0×10<sup>-3</sup>. The true swelling rate, in nm s<sup>-1</sup>, was determined by the chemical nature of the matrix; all dioxolane-containing materials exhibited swelling rates ~1.5 - 2 nm s<sup>-1</sup> compared to ~3 nm s<sup>-1</sup> for Nafion. Likewise, Nafion underwent relaxation at twice the rate of the fastest-relaxing dioxolane ionomer. Reduced swelling and relaxation kinetics are due to limited matrix segmental mobility of the dioxolane-containing ionomers. We demonstrate that changes in conductivity are strongly tied to the polymer relaxation, revealing the decoupled roles of initial swelling and relaxation on hydration, nanostructure, and ion transport in perfluorinated ionomers. </p>

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