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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 ...
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 ...
An example of a less common radical 1,2-shift can be found in the gas phase pyrolysis of certain polycyclic aromatic compounds. [4] The energy required in an aryl radical for the 1,2-shift can be high (up to 60 kcal / mol or 250 kJ /mol) but much less than that required for a proton abstraction to an aryne (82 kcal/mol or 340 kJ/mol).
Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). [1] Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation.
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 ...
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).