PUC Karnataka Science Class 12Department of Pre-University Education, Karnataka
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Which One of the Following Has the Highest Dipole Moment? - PUC Karnataka Science Class 12 - Chemistry

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Question

Which one of the following has the highest dipole moment?

(i) CH2Cl2

(ii) CHCl3

(iii) CCl4

Solution 1

1) 

Dichlormethane (CH2Cl2)

μ = 1.60D

2)

Chloroform (CHCl3)

μ = 1.08D

3)

Carbon tetrachloride (CCl4)

μ = 0D

CCl4 is a symmetrical molecule. Therefore, the dipole moments of all four C−Cl bonds cancel each other. Hence, its resultant dipole moment is zero.

As shown in the above figure, in CHCl3, the resultant of dipole moments of two C−Cl bonds is opposed by the resultant of dipole moments of one C−H bond and one C−Cl bond. Since the resultant of one C−H bond and one C−Cl bond dipole moments is smaller than two C−Cl bonds, the opposition is to a small extent. As a result, CHCl3 has a small dipole moment of 1.08 D.

On the other hand, in case of CH2Cl2, the resultant of the dipole moments of two C−Cl bonds is strengthened by the resultant of the dipole moments of two C−H bonds. As a result, CH2Cl2 has a higher dipole moment of 1.60 D than CHCl3 i.e., CH2Cl2 has the highest dipole moment.

Hence, the given compounds can be arranged in the increasing order of their dipole moments as:

CCl4 < CHCl3 < CH2Cl2

Solution 2

The three dimensional structures of the three compounds along with the direction of dipole moment in each of their bonds are given below:

CCl4 being symmetrical has zero dipole moment. In CHCl3, the resultant of two C – Cl dipole moments is opposed by the resultant of C – H and C – Cl bonds. Since the dipole moment of latter resultant is expected to be smaller than the former, CHCl3 has a finite dipole (1.03 D) moment.
In CH2CI2, the resultant of two C – Cl dipole moments is reinforced by resultant of two C – H dipoles, therefore, CH2CI2 (1 .62 D) has a dipole moment higher than that of CHCl3. Thus, CH2CI2 has highest dipole moment.

 

  Is there an error in this question or solution?

APPEARS IN

 NCERT Solution for Chemistry Textbook for Class 12 (2018 to Current)
Chapter 10: Haloalkanes and Haloarenes
Q: 4 | Page no. 311
Solution Which One of the Following Has the Highest Dipole Moment? Concept: Haloalkanes and Haloarenes - Nature of C-x Bond.
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