Table of Contents
- 1 Which substituent is an ortho para director in electrophilic aromatic substitution reactions?
- 2 Why are halogen substituents ring deactivating and yet ortho and para directing towards electrophilic aromatic substitution reactions?
- 3 What are activating and deactivating substituents?
- 4 Why is halogen atom attached to benzene ring is ortho and para directing but deactivating in nature?
- 5 How many constitutional isomers can be formed from a mono-substituted benzene ring?
Which substituent is an ortho para director in electrophilic aromatic substitution reactions?
Activating groups
| Magnitude of activation | Substituent Name (in approximate order of activating strength) | Directing effect |
|---|---|---|
| Strong | (substituted) amino groups | ortho, para |
| hydroxy and alkoxy groups | ||
| Moderate | acylamido groups | |
| acyloxy groups |
Which substituents is ortho para directing and activating to the benzene ring?
The methoxy group is an example of groups that are ortho, para directors by having and oxygen or nitrogen adjacent to the aromatic ring. This same activation is present with alcohols, amines, esters and amides (with the oxygen or nitrogen attached to the ring, not the carbonyl).
What happens to a compound that undergoes electrophilic aromatic substitution?
Aromatic compounds react by electrophilic aromatic substitution reactions, in which the aromaticity of the ring system is preserved. For example, benzene reacts with bromine to form bromobenzene. Many functional groups can be added to aromatic compounds via electrophilic aromatic substitution reactions.
Why are halogen substituents ring deactivating and yet ortho and para directing towards electrophilic aromatic substitution reactions?
Halogens are very electronegative. This means that inductively they are electron withdrawing. However, because of their ability to donate a lone pair of electrons in resonance forms, they are activators and ortho/para directing. Because they are electron withdrawing, halogens are very weak activators.
Which of the following substituent is an ortho and para director and ring deactivating *?
Chlorine donate its lone pair to the aromatic ring and hence increase the electron density at ortho and para position. Therefore, chlorine is a deactivating group.
Which of the following substituents is an ortho and para director and ring deactivating *?
What are activating and deactivating substituents?
Activating groups are substituents that increase the rate of a reaction (by lowering the activation energy). Deactivating groups are substituents that decrease the rate of a reaction (by increasing the activation energy). In contrast, electron-withdrawing groups decrease the reactivity of nucleophiles.
Why does benzene undergo electrophilic substitution?
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.
Does benzene undergo addition reactions?
Benzene, C6H6, is a planar molecule containing a ring of six carbon atoms each with a hydrogen atom attached. The presence of the delocalised electrons makes benzene particularly stable. Benzene resists addition reactions because that would involve breaking the delocalisation and losing that stability.
Why is halogen atom attached to benzene ring is ortho and para directing but deactivating in nature?
Halogens bonded to benzene ring has three lone pairs. These three electron pairs can cause resonance in benzene ring. But, halogens are also highly electronegative and thus they have strong -I effect. So, they are deactivating groups.
Which of the following benzene ring substituents are deactivating and meta directing?
-Cl,-N≡O are moderately deactivating but O, P-directing. -NO2,-OCH3 are meta directing .
What are the relative positions of a benzene ring with a substitution?
When a benzene ring with a substituent undergoes an electrophilic aromatic substitution, the electrophile is installed on a specific position (s) depending on the substituent. There are three relative positions for a disubstituted benzene ring: ortho, meta, and para. All the functional groups are divided into ortho-, para or meta-directors.
How many constitutional isomers can be formed from a mono-substituted benzene ring?
Since a mono-substituted benzene ring has two equivalent ortho-sites, two equivalent meta-sites and a unique para-site, three possible constitutional isomers may be formed in such a substitution. If reaction occurs equally well at all available sites, the expected statistical mixture of isomeric products would be 40\% ortho, 40\% meta and 20\% para.
Where do deactivated aromatic rings undergo electrophilic aromatic substitution?
In the previous post, we saw that a benzene ring with an activator undergoes electrophilic aromatic substitution at the ortho and para positions, while deactivated aromatic rings react at the meta position: Here is an interesting question: Where does the substitution occur if there are two groups on the benzene ring (disubstituted benzene)?
How do Nitro substituents affect the reactivity of benzene rings?
In contrast, a nitro substituent decreases the ring’s reactivity by roughly a million. This activation or deactivation of the benzene ring toward electrophilic substitution may be correlated with the electron donating or electron withdrawing influence of the substituents, as measured by molecular dipole moments.