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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 ...
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. Nucleophilic describes the affinity of a nucleophile to bond with positively charged ...
The electron pair (:) from the nucleophile (Nuc:) attacks the substrate (R−LG), forming a new covalent bond Nuc−R−LG. The prior state of charge is restored when the leaving group (LG) departs with an electron pair. The principal product in this case is R−Nuc. In such reactions, the nucleophile is usually electrically neutral or ...
A classic example of NGP is the reaction of a sulfur or nitrogen mustard with a nucleophile, the rate of reaction is much higher for the sulfur mustard and a nucleophile than it would be for a primary or secondary alkyl chloride without a heteroatom. [5] Ph−S−CH 2 −CH 2 −Cl reacts with water 600 times faster than CH 3 −CH 2 −CH 2 ...
A later paper by Edwards and Pearson, following research done by Jencks and Carriuolo in 1960 [8] [9] led to the discovery of an additional factor in nucleophilic reactivity, which Edwards and Pearson called the alpha effect, [7] where nucleophiles with a lone pair of electrons on an atom adjacent to the nucleophilic center have enhanced ...
In chemistry, a nucleophilic substitution (S N) is a class of chemical reactions in which an electron-rich chemical species (known as a nucleophile) replaces a functional group within another electron-deficient molecule (known as the electrophile). The molecule that contains the electrophile and the leaving functional group is called the substrate.
The first isolation of a nucleophilic aluminium center was achieved in 2018 by Aldridge, Goicoechea and coworkers when they were able to synthesize the first aluminyl anion, [5] following the discoveries of gallium [6] [7] [8] and indium [9] analogues, heavier group 13 analogues which are more stable than aluminium in the lower +1 oxidation ...
The discovery and categorization of heterolytic bond fission was clearly dependent on the discovery and categorization of the chemical bond. In 1916, chemist Gilbert N. Lewis developed the concept of the electron-pair bond, in which two atoms share one to six electrons, thus forming the single electron bond, a single bond, a double bond, or a triple bond. [3]