1. A Review of General Chemistry

In most amines, the nitrogen atom is sp³ hybridized, with a pyramidal structure and bond angles close to 109°. In urea, both nitrogen atoms are found to be planar, with bond angles close to 120°. Explain this surprising finding. (Hint: Consider resonance forms and the overlap needed in them.)

Predict the hybridization, geometry, and bond angles for the carbon and nitrogen atoms in acetonitrile (CH₃–C≡N:).

Describe the orbitals used in bonding and the bond angles in the following compounds:

e. BF₃

Predict the approximate bond angles in

a. the methyl cation.

b. the methyl radical.

c. the methyl anion.

Predict the approximate bond angles for the following:

c. the C—C—N bond angle in CH₃C≡N

d. the C—C—N bond angle in CH₃CH₂NH₂

Circle the coplanar atoms in the following structure:

For each of the following compounds and ions,

1. Draw a Lewis structure.

2. Show the kinds of orbitals that overlap to form each bond.

3. Give approximate bond angles around each atom except hydrogen.

c. CH₂=N–CH₃

You drew the Lewis structures of the following compounds and ion in Assessment 2.32. Predict their shapes around the central atom based on the Lewis structure.

(d) CO₃^2-

Predict the approximate size of the following bond angles.

(b) the C—N—C bond angle in a secondary amine

You drew the Lewis structures of the following compounds and ion in Assessment 2.32. Predict their shapes around the central atom based on the Lewis structure.

(c) HCO₂H

Describe the orbitals used in bonding and the bond angles in the following compounds:

a. CH₃O^-

What is the hybridization of all the atoms (other than hydrogen) in each of the following?

What are the bond angles around each atom?

c. ^-CH₃

d. ⋅CH₃

For each of the following molecules, indicate the hybridization of each carbon and give the approximate values of all the bond angles:

b. CH₃CH═CH₂

a. Which of the species have bond angles of 109.5°?

b. Which of the species have bond angles of 120°?

NH₃ ⁺NH₄ ^-CH₃

Predict the approximate size of the following bond angles.

(a) the C—O—C bond angle in an ether