Kinetics and thermodynamics of reversible disproportionation-comproportionation in redox triad oxoammonium cations - nitroxyl radicals - hydroxylamines
作者:Vasily D. Sen’、Ivan V. Tikhonov、Leonid I. Borodin、Evgeny M. Pliss、Valery A. Golubev、Mikhail A. Syroeshkin、Alexander I. Rusakov
DOI:10.1002/poc.3392
日期:2015.1
reduction potentials of nitroxyl radicals to hydroxylamines E1/3Σ and bond dissociation energies D(O–H) for hydroxylamines R2NOH in water were determined. For a wide variety of piperidine‐ and pyrrolidine‐1‐oxyls values of pK3H+ and ER2NO+/R2NO• correlate with each other, as well as with the equilibrium constants K4 and the inductive substituent constants σI. The correlations obtained allow prediction
这些化合物的氧化还原和酸碱性质定义了环硝氧基自由基R 2 NO •与氧铵阳离子R 2 NO +和羟胺R 2 NOH的酸催化歧化反应的动力学和平衡。在最近的工作中(J. Phys。Org。Chem。2014,27,114-120),我们表明R 2 NO •在酸性介质中的动力学稳定性取决于硝酰基的碱性。在这里,我们研究了R 2 NO +和R 2 NOH与R 2 NO •的反比例歧化反应的动力学。并且发现取代基的-I效应的增加大大降低了反应K 4的总体平衡常数。这是由于羟基铵阳离子K 3H +的酸度常数的增加和氧铵阳离子E R2NO + / R2NO•与硝酰基自由基E R2NO•/ R2NOH的还原电位之间的差异所致。测定了水中羟胺E 1 /3Σ还原电位的pH依赖性以及羟胺R 2 NOH的键解离能D(OH)。对于各种各样的哌啶和吡咯烷-1-氧基值,p K3H +和ë R2NO + / R2NO•归属关系彼此,以及与平衡常数ķ