Question

Dipole moment of p-nitroaniline when compared to nitrobenzene(X) and aniline(Y) will be
A) smaller than both
B)greater than both
C) greater than Y but smaller than X
D) Equal to zero

Answer 1

Answer:ans Wil be option c

Explanation:

Answer 2

Let us compare Dipole moment of p-nitroaniline ,nitrobenzene(X)  aniline(Y)

B)greater than both

Explanation:

Dipole moment

Polarity is measured in terms of dipole moment that is:  

 

 Dipole moment gives information about  structure of molecule.

• If dipole moment is zero, than the molecule is non polar.

• If dipole moment is not zero, than the polar molecule.  

Dipole Moment and Molecular Structure  

Let us consider:  

1. Diatomic molecule: Its structure is generally linear.  Dipole is zero.

 

2. Polyatomic molecule : Their dipole moment depends upon the structure. As we know, dipole moment is vector quantity. Therefore, they will get added.  

let us have a glance on  dipole moment of Ammonia and Nitrogen tri-fluoride:

• In Ammonia, the H being less electronegative than N. All the electrons are directed towards Nitrogen. As a result, the vectors add and give the final  dipole moment.
• In case of NF3, F being more electronegative than N. All the electrons  face opposite to F. Now the  vectors are subtracted. Due to this reason NH3 has more dipole moment than NF3.

Importance of Dipole Moment

1. It gives distinction between polar and non polar bonds.

• If dipole moment is 0, than non -polar.

• If not zero, than it is polar.  

2. It tells us about degree of polarity.

3. It gives information about shapes of the molecules.  

4. It gives percentage of ionic character in covalent bond. As we know, all ionic bonds have covalent character likewise all covalent bonds have ionic character in them.  

5. In covalent H-Cl bond, the bond is covalent, but it has ionic character in it due to difference in their electro-negativities.

6. If electronegativity difference is 1.7, than the bond have 50% ionic and 50% covalent character.  

7. If electronegativity difference is less than 1.7, than the bond is covalent.

8. If electronegativity difference is more than 1.7, than it is ionic.  

• In aniline net dipole moment downwards coz N donate it's lone pair to benzene  
• In nitro benzene: The  Nitrogen has the ability to  withdraw the electron from benzene ring as  a result of  -I and -R effect..
• In case of p-nitro aniline, the amine group attached donates the electron
• In  nitro group it withdraw the electrons  therefore , a net downward dipole moment which will be more than other

On the basis of this : It can be predicted that the correct answer for above asked question is option 2