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Benzyl is not to be confused with phenyl with the formula C 6 H 5. The term benzylic is used to describe the position of the first carbon bonded to a benzene or other aromatic ring. For example, (C 6 H 5)(CH 3) 2 C + is referred to as a "benzylic" carbocation. The benzyl free radical has the formula C 6 H 5 CH 2 •.
The benzilic acid rearrangement is formally the 1,2-rearrangement of 1,2-diketones to form α-hydroxy–carboxylic acids using a base.This reaction receives its name from the reaction of benzil with potassium hydroxide to form benzilic acid.
Benzylic cations of chromium arene complexes are conformationally stable, and undergo only exo attack to afford S N 1 products stereospecifically, with retention of configuration. [1] Propargyl [ 1 ] and oxonium [ 1 ] cations undergo retentive substitution reactions, and even β carbocations react with a significant degree of retention.
A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium CH + 3, methanium CH + 5, acylium ions RCO +, and vinyl C ...
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]
For the intermolecular case, the reaction is limited to tertiary alkylating agents, some secondary alkylating agents (ones for which carbocation rearrangement is degenerate), or alkylating agents that yield stabilized carbocations (e.g., benzylic or allylic ones).
A 1,2-rearrangement is an organic reaction where a substituent moves from one atom to another atom in a chemical compound. In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible.
If the potential carbocation can not be stabilized, ether cleavage follows a bimolecular, concerted S N 2 mechanism. In the example, the ether oxygen is reversibly protonated. The halide ion (here bromide) then nucleophilically attacks the sterically less hindered carbon atom, thereby forming methyl bromide and 1-propanol.