Search results for "Resonance effect"

showing 3 items of 3 documents

Predominance of inductive over resonance substituent effect on33S NMR chemical shifts of 4-substituted phenyl-4′-methylphenacyl sulfones

1999

33S NMR chemical shifts have been determined for the first time for a series of 10 substituted phenacyl sulfones. Electron-withdrawing and electron-releasing substituents in 4-substituted phenyl-4′-methylphenacyl sulfones, p-MeC6H4COCH2SO2C6H4R-p, cause a ‘reverse’ substituent effect on the 33S NMR resonance. Dual-substituent parameter (DSP) analysis of δ(33S) values revealed that the inductive effect of the substituent predominates over its resonance effect. This finding shows that the 33S NMR chemical shifts are of importance in estimating the electronic properties of sulfur-containing compounds. The 13C and 17O NMR chemical shifts of the title compounds are also discussed. Copyright © 19…

ChemistryStereochemistryCarbon-13 NMR satelliteChemical shiftSubstituentGeneral ChemistryCarbon-13 NMRResonance (chemistry)PhenacylMedicinal chemistrychemistry.chemical_compoundGeneral Materials ScienceInductive effectResonance effectMagnetic Resonance in Chemistry
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Neutrino Coannihilation on Dark-Matter Relics?

2006

High-energy neutrinos may resonate with relic background neutralinos to form short-lived sneutrinos. In some circumstances, the decay chain that leads back to the lightest supersymmetric particle would yield few-GeV gamma rays or charged-particle signals. Although resonant coannihilation would occur at an appreciable rate in our galaxy, the signal in any foreseeable detector is unobservably small.

PhysicsNuclear and High Energy PhysicsParticle physicsAstrophysics::High Energy Astrophysical PhenomenaAstrophysics (astro-ph)Dark matterHigh Energy Physics::PhenomenologyGamma rayFOS: Physical sciencesAstrophysicsAstrophysicsLightest Supersymmetric ParticleGalaxyHigh Energy Physics - PhenomenologyHigh Energy Physics - Phenomenology (hep-ph)High Energy Physics::ExperimentDecay chainNeutrinoResonance effect
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Relation between resonance energy and substituent resonance effect inP-phenols

2005

Molecular geometries of phenol and its 17 p-substituted derivatives were optimized at the B3LYP/6–311 + G** level of theory. Three homodesmotic and three isodesmotic reaction schemes were used to estimate aromatic stabilization energies (ASE) and the substituent effect stabilization energy (SESE). Other descriptors of π-electron delocalization (HOMA and NICS, NICS(1) and NICS(1)zz) were also estimated. The SESE and ASE values correlated well with one another as well as with substituent constants. Much worse correlations with substituent constants were found for other aromaticity indices. The NICS(1)zz values are the most negative for unsubstituted phenol, indicating its highest aromaticity;…

chemistry.chemical_compoundDelocalized electronMolecular geometryChemistryComputational chemistryOrganic ChemistrySubstituentPhenolAromaticityPhenolsPhysical and Theoretical ChemistryResonance (chemistry)Resonance effectJournal of Physical Organic Chemistry
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