1. A Review of General Chemistry

Which of the following molecules would you expect to have a dipole moment of zero?

g. BeCl₂

h. BF₃

If the dipole moment of CH₃F is 1.847 D and the dipole moment of CD₃F is 1.858 D, which is more electronegative: hydrogen or deuterium?

Account for the difference in the shape and color of the potential maps for ammonia and the ammonium ion in Section 1.11.

<IMAGE>

Rank the bonds from most polar to least polar.

d. C—H, C—C, C—N

Rank the bonds from most polar to least polar.

c. H—O, H—N, H—C

Rank the bonds from most polar to least polar.

b. C—Cl, C—I, C—Br

Which of the following molecules would you expect to have a dipole moment of zero?

d. NH₃

e. H₂C═CH₂

f. H₂C═CHBr

According to the potential map for the ammonium ion <IMAGE>, which atom has the greatest electron density?

Two isomers of 1,2-dichloroethene are known. One has a dipole moment of 2.4 D; the other has zero dipole moment. Draw the two isomers, and explain why one has zero dipole moment.

CHCl=CHCl 1,2-dichloroethene

1. Draw the Lewis structure.

2. Show how the bond dipole moments (and those of any nonbonding pairs of electrons) contribute to the molecular dipole moment.

3. Estimate whether the compound will have a large, small, or zero dipole moment.

g. HCN

h. CH₃CHO

i. H₂C=NH

1. Draw the Lewis structure.

2. Show how the bond dipole moments (and those of any nonbonding pairs of electrons) contribute to the molecular dipole moment.

3. Estimate whether the compound will have a large, small, or zero dipole moment.

d. CH₃F

e. CF₄

f. CH₃OH

Sulfur dioxide has a dipole moment of 1.60 D. Carbon dioxide has a dipole moment of zero, even though C―O bonds are more polar than S―O bonds. Explain this apparent contradiction.

A single bond between two carbons with different hybridizations has a small dipole. What is the direction of the dipole in the indicated bonds?

a.

b.

For each of the following compounds,

1. draw the Lewis structure.

2. show how the bond dipole moments (and those of any nonbonding pairs of electrons) contribute to the molecular dipole moment.

3. estimate whether the compound will have a large, small, or zero dipole moment.

a. CH₃CH=NCH₃

b. CH₃CH₂OH

c. CBr₄

The C=O double bond has a dipole moment of about 2.4 D and a bond length of about 1.23 Å.

b. Use this information to evaluate the relative importance of the following two resonance contributors: