How do substituents affect aromaticity?
It has been shown that the less aromatic the system, the stronger the substituent influence on its π-electron structure. In all cases, when the substituent changes number of π-electrons in the ring in the direction of 4N+2, its aromaticity increases.
What is the effect of substituent?
Substituent effects are the changes on a reaction or property in the unchanged part of the molecule resulting from substituent variation. Some Reactions or Properties.
What are the electronic effects of substituent?
Alkyl substituents (e.g. -CH3, -CH2CH3) are also electron donating groups – they activate the aromatic ring by increasing the electron density on the ring through an inductive donating effect. This is the same effect that allows alkyl groups to stabilise simple carbocations.
Which effect does substituent on aromatic electrophilic substitution?
Because benzene acts as a nucleophile in electrophilic aromatic substitution, substituents that make the benzene more electron-rich can accelerate the reaction. Substituents that make the benzene moor electron-poor can retard the reaction.
What is the effect of substituent on the rate of electrophilic aromatic substitution?
Each substituent either increases or decreases the electron density in the benzene ring, and this affects the course of electrophilic aromatic substitution. Donation of electron density to the ring makes benzene more electron rich and more likely to react with an electrophile.
When effect does substituent on aromatic electrophilic substitution?
Experiments have shown that substituents on a benzene ring can influence reactivity in a profound manner. For example, a hydroxy or methoxy substituent increases the rate of electrophilic substitution about ten thousand fold, as illustrated by the case of anisole in the virtual demonstration (above).
How do substituents affect electrophilic aromatic substitution?
Which compound reacts fastest in electrophilic aromatic substitution?
Lewis Acids Accelerate The Rate of Electrophilic Aromatic Substitution Reactions. The reaction of Cl2 with benzene is faster than toenail growth, but not by much [ref] (It is, however, much faster with more electron-rich aromatics such as toluene and phenol).
When considering electrophilic aromatic substitution reactions electron withdrawing substituents are described as?
Electron donating groups are generally ortho/para directors for electrophilic aromatic substitutions, while electron withdrawing groups are generally meta directors with the exception of the halogens which are also ortho/para directors as they have lone pairs of electrons that are shared with the aromatic ring.
Why does benzene give electrophilic substitution reaction?
Benzene is a planar molecule having delocalized electrons above and below the plane of the ring. Hence, it is electron-rich. As a result, it is highly attractive to electron-deficient species i.e., electrophiles. Therefore, it undergoes electrophilic substitution reactions very easily.
How do substituents affect acidity?
Electronegative substituents increase acidity by inductive electron withdrawal. As expected, the higher the electronegativity of the substituent the greater the increase in acidity (F > Cl > Br > I), and the closer the substituent is to the carboxyl group the greater is its effect (isomers in the 3rd row).