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Factors that influence the reaction rate include: Basicity - The ideal pKa range is 5-8 and the reaction either does not proceed, or proceeds poorly outside of this range. The reaction occurs faster under more basic conditions but only up to a point because when electron density builds up on the α-carbon, it makes it less electrophilic.
This makes the reaction even slower by having adjacent formal charges on carbon and nitrogen or 2 formal charges on a localised atom. Doing an electrophilic substitution directly in pyridine is nearly impossible. In order to do the reaction, they can be made by 2 possible reactions, which are both indirect.
Some electrophilic substitutions on the pyridine are usefully effected using pyridine N-oxide followed by deoxygenation. Addition of oxygen suppresses further reactions at nitrogen atom and promotes substitution at the 2- and 4-carbons.
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 ...
Electrophilic amination reactions can be classified as either additions or substitutions. Although the resulting product is not always an amine, these reactions are unified by the formation of a carbon–nitrogen bond and the use of an electrophilic aminating agent.
This reaction is similar to nucleophilic aliphatic substitution where the reactant is a nucleophile rather than an electrophile. The four possible electrophilic aliphatic substitution reaction mechanisms are S E 1, S E 2(front), S E 2(back) and S E i (Substitution Electrophilic), which are also similar to the nucleophile counterparts S N 1 and ...
Therefore, they are generated by adding iron filings to bromine or chlorine. Here is the mechanism of this reaction: The mechanism for bromination of benzene. The mechanism for iodination is slightly different: iodine (I 2) is treated with an oxidizing agent such as nitric acid to obtain the electrophilic iodine ("I +", probably IONO 2).
Aromatic nucleophilic substitution. This reaction differs from a common S N 2 reaction, because it happens at a trigonal carbon atom (sp 2 hybridization). The mechanism of S N 2 reaction does not occur due to steric hindrance of the benzene ring. In order to attack the C atom, the nucleophile must approach in line with the C-LG (leaving group ...