45842-10-2Relevant articles and documents
Thermal decay of TEMPO in acidic media via an N-oxoammonium salt intermediate
Ma, Yun,Loyns, Colin,Price, Peter,Chechik, Victor
, p. 5573 - 5578 (2011)
Disproportionation of TEMPO in acids leads to the formation of an N-oxoammonium salt, which can further decompose under thermal conditions, yielding the corresponding hydroxylamine, N2O, CO2 and a series of dimerisation products. Overall, acid-catalysed thermal decay of TEMPO leads to ca. 80% yield of hydroxylamine.
The effect of viscosity on the coupling and hydrogen-abstraction reaction between transient and persistent radicals
Li, Xiaopei,Kato, Tatsuhisa,Nakamura, Yasuyuki,Yamago, Shigeru
supporting information, p. 966 - 972 (2021/04/29)
The effect of viscosity on the radical termination reaction between a transient radical and a persistent radical undergoing a coupling reaction (Coup) or hydrogen abstraction (Abst) was examined. In a non-viscous solvent, such as benzene (bulk viscosity bulk 99% Coup/Abst selectivity, but Coup/Abst decreased as the viscosity increased (89/11 in PEG400 at 25 °C [bulk = 84 mPa s]). While bulk viscosity is a good parameter to predict the Coup/Abst selectivity in each solvent, microviscosity is the more general parameter. Poly(methyl methacrylate) (PMMA)-end radicals had a more significant viscosity effect than polystyrene (PSt)-end radicals, and the Coup/Abst ratio of the former dropped to 50/50 in highly viscous media (bulk = 3980 mPa s), while the latter maintained high Coup/ Abst selectivity (84/16). These results, together with the low thermal stability of dormant PMMA-TEMPO species compared with that of PSt-TEMPO species, are attributed to the limitation of the nitroxide-mediated radical polymerization of MMA. While both organotellurium and bromine compounds were used as precursors of radicals, the former was superior to the latter for the clean generation of radical species.
Controlling the Reactivity of a Metal-Hydroxo Adduct with a Hydrogen Bond
Day, Victor W.,Hessefort, Logan,Jackson, Timothy A.,Opalade, Adedamola A.
supporting information, p. 15159 - 15175 (2021/09/29)
The enzymes manganese lipoxygenase (MnLOX) and manganese superoxide dismutase (MnSOD) utilize mononuclear Mn centers to effect their catalytic reactions. In the oxidized MnIIIstate, the active site of each enzyme contains a hydroxo ligand, and X-ray crystal structures imply a hydrogen bond between this hydroxo ligand and aciscarboxylate ligand. While hydrogen bonding is a common feature of enzyme active sites, the importance of this particular hydroxo-carboxylate interaction is relatively unexplored. In this present study, we examined a pair of MnIII-hydroxo complexes that differ by a single functional group. One of these complexes, [MnIII(OH)(PaPy2N)]+, contains a naphthyridinyl moiety capable of forming an intramolecular hydrogen bond with the hydroxo ligand. The second complex, [MnIII(OH)(PaPy2Q)]+, contains a quinolinyl moiety that does not permit any intramolecular hydrogen bonding. Spectroscopic characterization of these complexes supports a common structure, but with perturbations to [MnIII(OH)(PaPy2N)]+, consistent with a hydrogen bond. Kinetic studies using a variety of substrates with activated O-H bonds, revealed that [MnIII(OH)(PaPy2N)]+is far more reactive than [MnIII(OH)(PaPy2Q)]+, with rate enhancements of 15-100-fold. A detailed analysis of the thermodynamic contributions to these reactions using DFT computations reveals that the former complex is significantly more basic. This increased basicity counteracts the more negative reduction potential of this complex, leading to a stronger O-H BDFE in the [MnII(OH2)(PaPy2N)]+product. Thus, the differences in reactivity between [MnIII(OH)(PaPy2Q)]+and [MnIII(OH)(PaPy2N)]+can be understood on the basis of thermodynamic considerations, which are strongly influenced by the ability of the latter complex to form an intramolecular hydrogen bond.
