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1. From what you remember of electronegativities, show the

Organic Chemistry | 8th Edition | ISBN: 9780321768414 | Authors: L.G. Wade Jr ISBN: 9780321768414 33

Solution for problem 35SP Chapter 1

Organic Chemistry | 8th Edition

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Organic Chemistry | 8th Edition | ISBN: 9780321768414 | Authors: L.G. Wade Jr

Organic Chemistry | 8th Edition

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Problem 35SP

1. From what you remember of electronegativities, show the direction of the dipole moments of the following bonds.

2. In each case, predict whether the dipole moment is relatively large (electronegativity difference ) or small.

(a) C-Cl

(b) C-H

(c) C-Li

(d) C-N

(e) C-O

(f) C-B

(g) C-Mg

(h) N-H

(i) O-H

(j) C-Br

Step-by-Step Solution:

Solution 35SP :

Step 1:

Electronegativity is the measure of tendency of an atom to attract a bonding pair of electrons towards itself. An atom's electronegativity is affected by its atomic number and the distance at which its valence electrons reside from the charged nucleus.

Dipole moment is a measure of the polarity of the molecule, i.e it is a measure of the separation of two electrically opposite charges. The difference in the electronegativity of the atoms or ions causes the dipole moment. Larger, the difference in electronegativity, larger is the dipole moment.

If the difference in electronegativity between two atoms or ions is less than 0.5, then the dipole moment is said to be small. If the difference in electronegativity between two atoms or ions is greater than 0.5, then the dipole moment is said to be large.

The direction of the dipole moment of a molecule is as shown below :

                

Here, the arrowhead of the symbol is always pointed towards the negative pole and the positive sign or plus sign is always towards the positive pole of the molecule.

Step 2:

(a) C-Cl :

        Electronegativity of C(Carbon) = 2.55

Electronegativity of Cl(Chlorine) = 3.16.

Electronegativity difference is = 3.16 - 2.55

                                 = 0.61

The electronegativity difference is greater than 0.5 and hence the dipole moment of C-Cl is large. Because the electronegativity of Cl is greater than the electronegativity of C, the direction of dipole moment is towards the Cl atom. Since Cl is more electronegative than C, it bears a partial negative charge() and C bears a partial positive charge of equal magnitude() . The dipole moment along with their partial charges is shown below :

Step 3:

(b) C-H :

Electronegativity of C(Carbon) = 2.55

Electronegativity of H(Hydrogen) = 2.2.

Electronegativity difference is = 2.55 - 2.2

                                 = 0.35

The electronegativity difference is less than 0.5 and hence the dipole moment of C-H is small. Because the electronegativity of C is greater than the electronegativity of H, the direction of dipole moment is towards the C atom and it bears a partial negative charge() and H bears a partial positive charge of equal magnitude() . The dipole moment along with their partial charges is shown below :

Step 4:

(c) C-Li :

Electronegativity of C(Carbon) = 2.55

Electronegativity of Li(Lithium) = 0.98.

Electronegativity difference is = 2.55 - 0.98

                                 = 1.57

The electronegativity difference is more than 0.5 and hence the dipole moment of C-Li is large. Because the electronegativity of C is greater than the electronegativity of Li, the direction of dipole moment is towards the C atom. Also, atom C gets a partial negative charge() as it is more electronegative than Li, and Li gets a partial positive charge of equal magnitude() . The dipole moment along with their partial charges is shown below :

                

        

Step 5:

(d) C-N :

Electronegativity of C(Carbon) = 2.55

Electronegativity of N(Nitrogen) = 3.04.

Electronegativity difference is = 3.04 - 2.55

                                 = 0.49

The electronegativity difference is less than 0.5 and hence the dipole moment of C-N is small. Because the electronegativity of N is greater than the electronegativity of C, the direction of dipole moment is towards the N atom. Also, atom N gets a partial negative charge() as it is more electronegative than C, and C gets a partial positive charge of equal magnitude() . The dipole moment along with their partial charges is shown below :

        

Step 6 :

(e) C-O :

Electronegativity of C(Carbon) = 2.55

Electronegativity of O(Oxygen) = 3.44.

Electronegativity difference is = 3.44 - 2.55

                                 = 0.89

The electronegativity difference is more than 0.5 and hence the dipole moment of C-O is large. Because the electronegativity of O is greater than the electronegativity of C, the direction of dipole moment is towards the O atom. Also, atom O gets a partial negative charge() as it is more electronegative than C, and C gets a partial positive charge of equal magnitude() . The dipole moment along with their partial charges is shown below :

        

Step 7 of 11

Chapter 1, Problem 35SP is Solved
Step 8 of 11

Textbook: Organic Chemistry
Edition: 8
Author: L.G. Wade Jr
ISBN: 9780321768414

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1. From what you remember of electronegativities, show the

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