Atom(s) which detach from the substrate during a chemical reaction
In chemistry, a leaving group is defined by the IUPAC as an atom or group of atoms that detaches from the main or residual part of a substrate during a reaction or elementary step of a reaction.[1] However, in common usage, the term is often limited to a fragment that departs with a pair of electrons in heterolytic bond cleavage.[2] In this usage, a leaving group is a less formal but more commonly used synonym of the term nucleofuge. In this context, leaving groups are generally anions or neutral species, departing from neutral or cationic substrates, respectively, though in rare cases, cations leaving from a dicationic substrate are also known.[3]
A species' ability to serve as a leaving group depends on its ability to stabilize the additional electron density that results from bond heterolysis. Common anionic leaving groups are halides such as Cl−, Br− and I−, and sulfonate esters such as tosylate (TsO−), while water (H2O), alcohols (R−OH), and amines (R3N) are common neutral leaving groups.
In the broader IUPAC definition, the term also includes groups that depart without an electron pair in a heterolytic cleavage (groups specifically known as an electrofuges), like H+ or SiR+3, which commonly depart in electrophilic aromatic substitution reactions.[1][4] Similarly, species of high thermodynamic stability like nitrogen (N2) or carbon dioxide (CO2) commonly act as leaving groups in homolytic bond cleavage reactions of radical species. A relatively uncommon term that serves as the antonym of leaving group is entering group (i.e., a species that reacts with and forms a bond with a substrate or a substrate-derived intermediate).
In this article, the discussions below mainly pertain to leaving groups that act as nucleofuges.
Common mechanistic contexts that involve the departure of a nucleofugal leaving group. The leaving group (LG) is shown in red. Top: SN2 reaction; middle/left: first step of SN1 and E1 reactions; middle/right: second step of E1cb, AAC2, and BAC2 reactions; bottom: E2 reaction.
though in rare cases, cations leaving from a dicationic substrate are also known. A species' ability to serve as a leavinggroup depends on its ability to...
an sp3-hybridised carbon atom via a backside attack, all while the leavinggroup detaches from the reaction center in a concerted (i.e. simultaneous)...
of the steps a phenol group is protected as its tosylate and the primary alcohol as its nosylate. The latter is a leavinggroup for displacement by diisopropylamine:...
the nucleophile attacks the substrate forming a new bond, while the leavinggroup departs with an electron pair. The nucleophile may be electrically neutral...
functional group within another electron-deficient molecule (known as the electrophile). The molecule that contains the electrophile and the leaving functional...
by addition of an appropriate aliphatic compound bearing a suitable leavinggroup (R–X). Although popular in textbooks, the method is usually impractical...
reaction in organic chemistry in which the nucleophile displaces a good leavinggroup, such as a halide, on an aromatic ring. Aromatic rings are usually nucleophilic...
three steps: Formation of a tert-butyl carbocation by separation of a leavinggroup (a bromide anion) from the carbon atom: this step is slow. Nucleophilic...
positive charge on an atom or a group of atoms. As it does so, it replaces a weaker nucleophile, which then becomes a leavinggroup; the remaining positive or...
functional group with the general structure CH3SO2O−R, abbreviated MsO−R, where R is an organic substituent. Mesylate is considered a leavinggroup in nucleophilic...
are sent to the group's multicast address. IGMPv2 accelerates the process of leaving a group and adjusts other timeouts. Leave-group messages are sent...
acid, already one of the strongest acids known. A triflate group is an excellent leavinggroup used in certain organic reactions such as nucleophilic substitution...
as reagents in organic synthesis, chiefly because the RSO3− group is a good leavinggroup, especially when R is electron-withdrawing. Methyl triflate...
Thiophenols are produced by S-arylation or the replacement of diazonium leavinggroup with sulfhydryl anion (SH−): ArN+ 2 + SH− → ArSH + N2 Akin to the chemistry...
once). In order for the SN2 reaction to take place there must be a good leavinggroup which is strongly electronegative, commonly a halide. In the Williamson...
epoxides are generated from carbonyl groups and sulfonium ylides. In this reaction, a sulfonium is the leavinggroup instead of chloride. Electron-deficient...
nucleophile, while an alkoxide is the leavinggroup. This reaction, saponification, is the basis of soap making. The alkoxide group may also be displaced by stronger...
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent...
Hofmann product is preferentially formed due to the steric bulk of the leavinggroup causing the hydroxide to abstract the more easily accessible hydrogen...
where the molecule is able to stabilize an anion but possesses a poor leavinggroup, a third type of reaction, E1CB, exists. Finally, the pyrolysis of xanthate...
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nucleophile – such as an alcohol, amine, or enolate – displaces the leavinggroup of an acyl derivative – such as an acid halide, anhydride, or ester...
related to Leaving Neverland. Official website Leaving Neverland on Channel 4 Leaving Neverland at IMDb Leaving Neverland at Metacritic Leaving Neverland...
follows: R-X + CH3O- → R-O-CH3 + X- where R represents an alkyl group and X is the leavinggroup (e.g., a halide). In esterification reactions, the methoxide...
Leave Means Leave was a pro-Brexit, Eurosceptic political pressure group organisation that campaigned and lobbied for the United Kingdom to leave the...
ketoximes and N-chloro/N-fluoro imines, with the migrating group being anti-periplanar to the leavinggroup on the nitrogen. Certain conditions have been known...
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