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The IUPAC acknowledges the three divergent definitions of carbonium ion and urges care in the usage of this term. For the remainder of this article, the term carbonium ion will be used in this latter restricted sense, while non-classical carbocation will be used to refer to any carbocation with C–C and/or C–H σ-bonds delocalized by bridging.
Compared to a ketone, the polarization of an oxocarbenium ion is accentuated: they more strongly resemble a "true" carbocation, and they are more reactive toward nucleophiles. In organic reactions, ketones are commonly activated by the coordination of a Lewis acid or Brønsted acid to the oxygen to generate an oxocarbenium ion as an intermediate.
The balance of these carbonate species (which ultimately affects the solubility of carbon dioxide), is dependent on factors such as pH, as shown in a Bjerrum plot.In seawater this is regulated by the charge balance of a number of positive (e.g. Na +, K +, Mg 2+, Ca 2+) and negative (e.g. CO 3 2− itself, Cl −, SO 4 2−, Br −) ions.
The 2-norbornyl cation is one of the best characterized carbonium ion. It is the prototype for non-classical ions. As indicated first by low-temperature NMR spectroscopy and confirmed by X-ray crystallography, [1] it has a symmetric structure with an RCH 2 + group bonded to an alkene group, stabilized by a bicyclic structure.
A carbocation may be stabilized by resonance by a carbon–carbon double bond or by the lone pair of a heteroatom adjacent to the ionized carbon. The allyl cation CH 2 =CH−CH + 2 and benzyl cation C 6 H 5 −CH + 2 are more stable than most other carbenium ions due to donation of electron density from π systems to the cationic center. [ 20 ]
Formation of a tert-butyl carbocation by separation of a leaving group (a bromide anion) from the carbon atom: this step is slow. [5] Recombination of carbocation with nucleophile. Nucleophilic attack: the carbocation reacts with the nucleophile. If the nucleophile is a neutral molecule (i.e. a solvent) a third step is required to complete the ...
In organic chemistry, a carbanion is an anion in which carbon is negatively charged. [1] [failed verification]Formally, a carbanion is the conjugate base of a carbon acid: . R 3 CH + B − → R 3 C − + HB
The vinyl cation is a carbocation with the positive charge on an alkene carbon. Its empirical formula of the parent ion is C 2 H + 3.Vinyl cation are invoked as reactive intermediates in solvolysis of vinyl halides, [1] [2] as well as electrophilic addition to alkynes and allenes.