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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 ...
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.
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 ...
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 contrast, C17-N2 bond (149.06 pm) is longer than N1-C1 bond (148.75 pm) and N1-C11 bond (147.85 pm) due to donation of O3 lone pair into σ* orbital of C17-N2. This model however is forced into tetracyclic sceleton, and tetrahedral O3 is methylated which makes it a poor model overall. N-brosylmitomycin A
In chemistry, S N i (substitution nucleophilic internal) refers to a specific, regio-selective but not often encountered reaction mechanism for nucleophilic aliphatic substitution. The name was introduced by Cowdrey et al. in 1937 to label nucleophilic reactions which occur with retention of configuration, [ 1 ] but later was employed to ...
The physical manifestation of leaving group ability is the rate at which a reaction takes place. Good leaving groups give fast reactions. By transition state theory, this implies that reactions involving good leaving groups have low activation barriers leading to relatively stable transition states.
Two common modes of Lewis acid catalysis in reactions with polar mechanisms. In reactions with polar mechanisms, Lewis acid catalysis often involves binding of the catalyst to Lewis basic heteroatoms and withdrawing electron density, which in turn facilitates heterolytic bond cleavage (in the case of Friedel-Crafts reaction) or directly activates the substrate toward nucleophilic attack (in ...