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2) is the conjugate base of imidazole. It is a nucleophile and a strong base. The free anion has C 2v symmetry. Imidazole has a pK a of 14.05, [1] so the deprotonation of imidazole (C 3 H 3 N 2 H) requires a strong base.
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 ...
Organometallic compounds of electropositive metals are superbases, but they are generally strong nucleophiles. Examples include organolithium and organomagnesium ( Grignard reagent ) compounds. Another type of organometallic superbase has a reactive metal exchanged for a hydrogen on a heteroatom , such as oxygen (unstabilized alkoxides ) or ...
Butyllithium is a strong base (pK b ≈ -36), but it is also a powerful nucleophile and reductant, depending on the other reactants. Furthermore, in addition to being a strong nucleophile, n -BuLi binds to aprotic Lewis bases, such as ethers and tertiary amines , which partially disaggregate the clusters by binding to the lithium centers.
While nucleophilic acyl substitution reactions can be base-catalyzed, the reaction will not occur if the leaving group is a stronger base than the nucleophile (i.e. the leaving group must have a higher pK a than the nucleophile). Unlike acid-catalyzed processes, both the nucleophile and the leaving group exist as anions under basic conditions.
tert-Butoxide, on the other hand, is a strong base, but a poor nucleophile, because of its three methyl groups hindering its approach to the carbon. Nucleophile strength is also affected by charge and electronegativity : nucleophilicity increases with increasing negative charge and decreasing electronegativity.
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as RO −, where R is the organyl substituent. Alkoxides are strong bases [citation needed] and, when R is not bulky, good nucleophiles and good ligands.
This observation led Pearson to develop his hard-soft acid-base theory, which is arguably the most important contribution that the Edwards equation has made to current understanding of organic and inorganic chemistry. [11] Nucleophiles, or bases, that were polarizable, with large α values, were categorized as “soft”, and nucleophiles that ...