Mise en evidence d'equilibres de coordinaurs/heterolyse pour les reactors reversibles entre carbocations et carbionions。Cette possibilite est etudiee avec les trimethyl- et triphenyl-cyclopropene-2yl nitro-4' phenyl malononitriles
Heterolysis and homolysis energies for some carbon-oxygen bonds
作者:Edward M. Arnett、Kalyani Amarnath、Noel G. Harvey、Sampath Venimadhavan
DOI:10.1021/ja00176a039
日期:1990.9
Methods described previously for obtaining heterolysis (ΔH het ) and homolysis (ΔH homo ) enthalpies for bonds that can be cleaved to produce resonance-stabilized carbeniumions, anions, and radicals are extended to the study of carbon-oxygen bonds through the reactions of resonance-stabilized carbeniumions with substituted phenoxide ions. Titration calorimetry was used to obtain the heat of heterolysis
先前描述的获得异裂 (ΔH het ) 和均裂 (ΔH homo ) 焓的方法可以裂解以产生共振稳定的碳正离子、阴离子和自由基,通过共振反应扩展到碳-氧键的研究- 稳定的碳正离子与取代的酚盐离子。滴定量热法用于获得异解热,二次谐波交流伏安法(SHACV)法用于获得阴离子的可逆氧化电位
Heats of reaction of resonance-stabilized carbenium ions with nitrogen bases
作者:Edward M. Arnett、Sampath Venimadhavan
DOI:10.1021/jo00008a031
日期:1991.4
Heats of reaction (DELTA-H(rxn) are reported for five resonance-stabilized carbenium ions with ten aliphatic amines and seven pyridines in sulfolane at 25-degrees-C to produce substituted ammonium ions. Heats of reaction (DELTA-H(rxn) for these neutral bases fall in the same range as the corresponding heats of reaction of the carbenium ions with a variety of resonance-stabilized anions (carbanions, and oxyanions) whose pK(a)S are comparable to those of the amines and pyridines. Although the DELTA-H(rxn)S do not correlate with the aqueous pK(BH)+S of the amines, good correlations are obtained using the pK(R)+S of the carbenium ions and with the gas-phase heats of reaction of the amines with trimethylboron. Also, the DELTA-H(rxn)S of pyridines with the carbenium ions correlate fairly well with the pK(R)+S of the carbenium ions and are surprisingly insensitive to steric hindrance.