Question

Which of the following have +M effect (e-donating mesomeric effect).
(This question has multiple correct options)
A. $- N{O_2}$
B. $- COOH$
C. $- N{H_2}$
D. $- SR$

Answer 1

In order to solve this question we have to know the mesomeric effect than we will be checking one by one all the options and check the +M effect and we will find in how of it will be showing the mesomeric effect.

Complete step-by-step answer: For solving this question we need to know the mesomeric effect:
The mesomeric effect in chemistry is a property of substituents or functional groups in a chemical compound. It is defined as the polarity produced in the molecule by the interaction of two pi bonds or between a pi bond and lone pair of electrons present on an adjacent atom.
Now we will be reading +M effect and –M effect:
+M effect:When the $\pi$ electrons are transferred from a particular group towards a conjugate system, this increases the electron density of the conjugate system then such a phenomenon is known as +M effect electron donating mesomeric effect. For the +M effect the group should have a lone pair or negative charge.
-M effect:When $\pi$ electron bond electrons are transferred from the conjugate system, then the phenomenon is known as negative isomeric effect.

So the appropriate answers are C and D.

Note: The molecules which are bonded which have double and triple bond and show –M effect whereas that have lone pair on the directly bonded atom shows +M effect.