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Formally, a carbanion is the conjugate base of a carbon acid: R 3 CH + B − → R 3 C − + HB. where B stands for the base. The carbanions formed from deprotonation of alkanes (at an sp 3 carbon), alkenes (at an sp 2 carbon), arenes (at an sp 2 carbon), and alkynes (at an sp carbon) are known as alkyl, alkenyl , aryl, and alkynyl anions ...
Both these studies show how Bent's rule can be used to aid synthetic chemistry. Knowing how molecular geometry accurately due to Bent's rule allows synthetic chemists to predict relative product stability. [14] [30] Additionally, Bent's rule can help chemists choose their starting materials to drive the reaction towards a particular product. [14]
The following other wikis use this file: Usage on ar.wikipedia.org أنيون كربوني; Usage on be.wikipedia.org Карбаніён; Usage on ca.wikipedia.org
Carbocation rearrangements are more common than the carbanion or radical counterparts. This observation can be explained on the basis of Hückel's rule. A cyclic carbocationic transition state is aromatic and stabilized because it holds 2 electrons. In an anionic transition state on the other hand 4 electrons are present thus antiaromatic and ...
It proceeds through a carbanion that attacks an endocyclic carbon and expels a leaving group (a halide) forming a bicyclic molecule with rings smaller than the original. The bicycle is then opened by nucleophilic attack on the ketone to give the contracted product. [ 19 ]
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The stability of alkyl-substituted carbocations follows the order 3° > 2° > 1° > methyl. This trend can be inferred by the hydride ion affinity values (231, 246, 273, and 312 kcal/mol for (CH 3) 3 C +, (CH 3) 2 CH +, CH 3 CH + 2, and CH + 3). [9] The effect of alkyl substitution is a strong one:
The nucleophilic carbanion center quickly undergoes carbolithiation to the double bond, generating an anion stabilized by the adjacent sulfone group. An intramolecular S N 2 reaction by the anion forms the cyclic backbone of morphine. [14] Synthesis of morphine using lithium–halogen exchange