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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.
Substitution reactions in organic chemistry are classified either as electrophilic or nucleophilic depending upon the reagent involved, whether a reactive intermediate involved in the reaction is a carbocation, a carbanion or a free radical, and whether the substrate is aliphatic or aromatic. Detailed understanding of a reaction type helps to ...
Structure of the 2-norbornyl cation, an iconic nonclassical ion. The structure was deduced from X-ray crystallography.C-C bond lengths not labeled are normal (ca. 1.5 Å).
Subsequently, others have used the term carbonium ion more narrowly to refer to species that are derived (at least formally) from electrophilic attack of H + or R + on an alkane, in analogy to other main group onium species, while a carbocation that contains any type of three-centered bonding is referred to as a non-classical carbocation. In ...
A carbanion is one of several reactive intermediates in organic chemistry. In organic synthesis, organolithium reagents and Grignard reagents are commonly treated and referred to as "carbanions." This is a convenient approximation, although these species are generally clusters or complexes containing highly polar, but still covalent bonds metal ...
If the charge in an organic ion is formally centred on a carbon, it is termed a carbocation (if positively charged) or carbanion (if negatively charged). Formation Monatomic ions are formed by the gain or loss of electrons to the valence shell (the outer-most electron shell) in an atom.
In S N 1, a leaving group is broken off to create a carbocation reaction intermediate. Then, a nucleophile attacks and forms a new bond with the carbocation intermediate to form the final, substituted product, as shown in the reaction of 2-bromo-2-methylpropane to form 2-methyl-2-propanol. [4] (CH 3) 3 CBr → (CH 3) 3 C + (CH 3) 3 C + + H 2 O ...
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 ]