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- Alpha_effect abstract "The alpha effect refers to the increased nucleophilicity of a molecule due to the presence of an adjacent (alpha) atom with lone pair electrons. The molecule does not necessarily exhibit increased basicity compared with a similar molecule without the adjacent, electron donating atom. The effect is well established with many theories to explain the effect but without a clear winner. The effect was first observed by Jencks and Carriuolo in 1960 in a series of chemical kinetics experiments involving the reaction of the ester p-nitrophenyl acetate with a range of nucleophiles. Regular nucleophiles such as the fluoride anion, aniline, pyridine, ethylene diamine and the phenolate ion were found to have pseudo first order reaction rates corresponding to their basicity as measured by their pKa. Other nucleophiles however reacted much faster than expected based on this criterion alone. These include hydrazine, hydroxylamine, the hypochlorite ion and the hydroperoxide anion. In 1962 Edwards and Pearson (the latter of HSAB theory) introduced the phrase alpha effect for this anomaly. He offered the suggestion that the effect was caused by a transition state (TS) stabilization effect: on entering the TS the free electron pair on the nucleophile moves away from the nucleus causing a partial positive charge which can be stabilized by an adjacent lone pair as for instance happens in any carbocation.Over the years many additional theories have been put forward attempting to explain the effect. A ground state stabilizing effect assumes that the alpha lone-pair and nucleophilic electron pair destabilize each other by electronic repulsion thereby increasing the ground state and making it more reactive. Stabilization of the transition state is possible by assuming some TS free radical character or assuming that the TS has more advanced nucleophile-substrate bond formation. The polarizability of the nucleophile or involvement of intramolecular catalysis also plays a role. One recent in silico contribution did find a correlation between the alpha effect and the so-called deformation energy which is the electronic energy required to bring the two reactants together in the transition state.The alpha effect is also dependent on solvent but not in a predictable way: it can increase or decrease with solvent mix composition or even go through a maximum.".
- Alpha_effect wikiPageID "6153032".
- Alpha_effect wikiPageLength "4036".
- Alpha_effect wikiPageOutDegree "31".
- Alpha_effect wikiPageRevisionID "659255421".
- Alpha_effect wikiPageWikiLink Acid_dissociation_constant.
- Alpha_effect wikiPageWikiLink Aniline.
- Alpha_effect wikiPageWikiLink Atom.
- Alpha_effect wikiPageWikiLink Base_(chemistry).
- Alpha_effect wikiPageWikiLink Basicity.
- Alpha_effect wikiPageWikiLink Carbocation.
- Alpha_effect wikiPageWikiLink Catalysis.
- Alpha_effect wikiPageWikiLink Category:Physical_organic_chemistry.
- Alpha_effect wikiPageWikiLink Chemical_kinetics.
- Alpha_effect wikiPageWikiLink Electron.
- Alpha_effect wikiPageWikiLink Ester.
- Alpha_effect wikiPageWikiLink Ethylene_diamine.
- Alpha_effect wikiPageWikiLink Ethylenediamine.
- Alpha_effect wikiPageWikiLink Fluoride.
- Alpha_effect wikiPageWikiLink Free_radical.
- Alpha_effect wikiPageWikiLink HSAB_theory.
- Alpha_effect wikiPageWikiLink Hydrazine.
- Alpha_effect wikiPageWikiLink Hydroperoxide.
- Alpha_effect wikiPageWikiLink Hydroxylamine.
- Alpha_effect wikiPageWikiLink Hypochlorite.
- Alpha_effect wikiPageWikiLink In_silico.
- Alpha_effect wikiPageWikiLink Intramolecular.
- Alpha_effect wikiPageWikiLink Intramolecular_reaction.
- Alpha_effect wikiPageWikiLink Lone_pair.
- Alpha_effect wikiPageWikiLink Molecule.
- Alpha_effect wikiPageWikiLink Nucleophile.
- Alpha_effect wikiPageWikiLink Organic_peroxide.
- Alpha_effect wikiPageWikiLink PKa.
- Alpha_effect wikiPageWikiLink Phenol.
- Alpha_effect wikiPageWikiLink Phenolate.
- Alpha_effect wikiPageWikiLink Polarizability.
- Alpha_effect wikiPageWikiLink Pseudo_first_order_reaction.
- Alpha_effect wikiPageWikiLink Pyridine.
- Alpha_effect wikiPageWikiLink Radical_(chemistry).
- Alpha_effect wikiPageWikiLink Ralph_Pearson.
- Alpha_effect wikiPageWikiLink Rate_equation.
- Alpha_effect wikiPageWikiLink Solvent.
- Alpha_effect wikiPageWikiLink Transition_state.
- Alpha_effect wikiPageWikiLinkText "Alpha effect".
- Alpha_effect wikiPageWikiLinkText "alpha effect".
- Alpha_effect hasPhotoCollection Alpha_effect.
- Alpha_effect wikiPageUsesTemplate Template:Reflist.
- Alpha_effect subject Category:Physical_organic_chemistry.
- Alpha_effect comment "The alpha effect refers to the increased nucleophilicity of a molecule due to the presence of an adjacent (alpha) atom with lone pair electrons. The molecule does not necessarily exhibit increased basicity compared with a similar molecule without the adjacent, electron donating atom. The effect is well established with many theories to explain the effect but without a clear winner.".
- Alpha_effect label "Alpha effect".
- Alpha_effect sameAs Alpha-Effekt.
- Alpha_effect sameAs Alfa-effect.
- Alpha_effect sameAs m.0fsxz4.
- Alpha_effect sameAs Q1492704.
- Alpha_effect sameAs Q1492704.
- Alpha_effect wasDerivedFrom Alpha_effect?oldid=659255421.
- Alpha_effect isPrimaryTopicOf Alpha_effect.