3744-25-0Relevant academic research and scientific papers
Understanding atom transfer radical polymerization: Effect of ligand and initiator structures on the equilibrium constants
Tang, Wei,Kwak, Yungwan,Braunecker, Wade,Tsarevsky, Nicolay V.,Coote, Michelle L.,Matyjaszewski, Krzysztof
, p. 10702 - 10713 (2008)
Equilibrium constants in Cu-based atom transfer radical polymerization (ATRP) were determined for a wide range of ligands and initiators in acetonitrile at 22°C. The ATRP equilibrium constants obtained vary over 7 orders of magnitude and strongly depend o
Factors influencing C-ON bond homolysis in alkoxyamines: Unexpected behavior of SG1 (N-(2-methyl-2-propyl)-N-(1-diethylphosphono-2,2-dimethylpropyl) -N-oxyl)-based alkoxyamines
Bertin, Denis,Gigmes, Didier,Le Mercier, Christophe,Marque, Sylvain R. A.,Tordo, Paul
, p. 4925 - 4930 (2007/10/03)
Alkoxyamines and persistent nitroxides are important regulators of nitroxide-mediated radical polymerization (NMP). Since the polymerization time decreases with the increasing equilibrium constant K (kdk c), i.e., the increasing rate constant kd of the homolysis of the C-ON bond between the polymer chain and the nitroxide moiety, the factors influencing the cleavage rate constants are of considerable interest. SG1-based alkoxyamines have turned out to be the most potent alkoxyamine family to use for NMP of various monomers. Therefore, it is of high interest to determine the factors which make SG1 derivatives better regulators than TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) derivatives. Contrary to what we had observed with TEMPO derivatives, we observed two relationships for the plot Ea vs BDE(C-H), one for the nonpolar released alkyl radicals (E a (kJ/mol) = -133.0 + 0.72BDE) and the other one for the polar released alkyl radicals (Ea (kJ/mol) = -137.0 + 0.69BDE). However, for both families (SG1 and TEMPO derivatives), the rate constants kd of the C-ON bond homolysis were correlated to the cleavage temperature T c (log(kd(s-1)) = 1.51 -0.058Tc). Such correlations should help to design new alkoxyamines to use as regulators and to improve the tuning of NMP experiments.
The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds
Denisov
, p. 2110 - 2116 (2007/10/03)
A parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C+OH + R1COR2 → >C=O + R1R2C+OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C+OH + R1CH=CH2 → >C=O + R1C+ HCH3; >R1CH=CH2 + R2C+HCH2R3 → R2C+HCH3 + R2CH=CHR3. These parameters were used to calculate the activation energies of these transformations. The kinetic parameters of reactions of hydrogen abstraction by free radicals and molecules (aldehydes, ketones, and quinones) from the C-H and O-H bonds were compared.
