نتایج جستجو برای: hammett constant
تعداد نتایج: 218513 فیلتر نتایج به سال:
[reaction: see text] A new method for the synthesis of 5-arylethynyl-8-hydroxyquinoline ligands using Sonogashira-Hagihara coupling was developed. The electronic nature of arylethynyl substituents affects the emission color and quantum yield of the resulting Al(III) complex. Photophysical properties of the metallocomplexes correspond to the electron-withdrawing/-donating character of the arylet...
A simple yet effective strategy for synthesis of 5-aryl-8-quinolinolate-based electroluminophores with tunable emission wavelengths is presented. Two different pathways for the attachment of electron-donating or electron-withdrawing aryl groups to the 5-position of the quinolinolate ligand via Suzuki coupling were developed. A successful tuning in the emission color was achieved: the emission w...
Dependence of the hydrolysis rate a series N-methoxy-2-phenyl-1,3-oxazinanes on Hammett substituent constant phenyl ring was determined, yielding reaction ρ=−1.40±0.05. Based this information, 4-(benzoyloxy)benzaldehyde selected as protecting group for new (2R,3S)-4-(methoxyamino)butane-1,2,3-triol phosphoramidite building block. The yield preparation block well its coupling in automated oligon...
An initial rate evaluation of the triazolium-catalysed benzoin condensation permitted a Hammett structure–activity analysis providing insight into rate-limiting step.
We report on the results of a systematic ab initio study of the Jones birefringence of noble gases, of furan homologues, and of monosubstituted benzenes, in the gas phase, with the aim of analyzing the behavior and the trends within a list of systems of varying size and complexity, and of identifying candidates for a combined experimental/theoretical study of the effect. We resort here to analy...
The kinetics of oxidation of a number of metaand para-substituted N,α-diphenylnitrones (nitrone) by dichloramine-T (DCT) was investigated in the presence of alkali in aqueous acetonitrile medium. The order with respect to DCT was one and to OHan inverse fractional order. The reaction was first order with respect to nitrone. Both electron releasing and withdrawing substituents suppress the react...
Kinetic studies of the reactions of α-bromoacetanilides [YC6H4NHC(=O)CH2Br] with substituted benzylamines (XC6H4CH2NH2) have been carried out in dimethyl sulfoxide at 35.0 C. The Hammett plots for substituent (Y) variations in the substrate (log kN vs. σY) are biphasic concave upwards/downwards with breaks at Y = 4-Cl (σY = 0.23). The Hammett coefficients ρY and the cross-interaction constant ρ...
A computational Hammett analysis of oxy-insertion into platinum-aryl bonds is performed. Modeled transformations involve the two-step conversion of [((X)bpy)Pt(R)(OY)](+) (R = p- or m-X-C(6)H(4); Y = 4- or 3-X-pyridine; (X)bpy = 4,4'- or 5,5'-X-bpy; X = NO(2), H, OMe, NMe(2)) proceeding through a Pt-oxo intermediate to form aryloxide [((X)bpy)Pt(OR)(Y)](+), which contrasts a one-step non-redox ...
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