Organic Chemistry Functional Groups and Electronic Effects Quiz

Study Notes

Mesomeric Effect Overview

The mesomeric effect refers to the delocalization of electrons in a molecule through resonance, affecting the stability and reactivity.
Two general types are recognized: +M (positive mesomeric) and -M (negative mesomeric) effects.

+M Effect

Groups with +M effect donate electron density through resonance, enhancing electron cloud in substituted benzene rings.
Common groups showing +M effect include:
- -OH (hydroxyl)
- -OCH3 (methoxy)
- -NH2 (amino)
- -NO2 (nitro) or -CN (cyano) in specific contexts can display mixed effects.

-M Effect Order

Functional groups exhibiting -M effect withdraw electron density through resonance.
In decreasing order of -M effect, typical groups include:
- -NO2 (nitro, strong -M)
- -CN (cyano)
- -F (fluoro)
- -Cl (chloro)
- -Br (bromo)
- -I (iodo)

Presence of Mesomeric Effect

Molecules containing functional groups that can resonate exhibit mesomeric effects.
Important examples with notable mesomeric effects:
- Phenols demonstrate +M through OH group.
- Anilines display +M via NH2 group.

Groups with +M and -I Effects

Certain groups can exhibit both positive mesomeric (+M) and negative inductive (-I) effects:
- -OCH3 (methoxy)
- -NH2 (amino)
- -NO2 (though primarily -M, also exhibits some +M)

+M Effect Groups on Benzene

Various groups attached to benzene that show +M effect include:
- Hydroxyl (-OH), alkoxy (-OCH3), amino (-NH2), and halogens (to a lesser extent).
The exact count can vary based on functional needs; commonly, 4-5 groups contribute distinctly to +M effects.

Description

Test your knowledge of organic chemistry functional groups and their electronic effects with this quiz. Identify and rank the groups based on their -M effect and determine the weakest +M group in the given species. This quiz is suitable for students studying organic chemistry.