Chem 3013-01
Problem Set 2
Due Jan 25 in Class
Complete the 10 problems below on separate paper. Clearly indicate the exercise number and
ensure all writing and illustrations are legible. Please write your name on all pages and submit a
stapled copy of your solutions.
1. Draw an energy diagram indicating the relative energies of the 1s, 2s, and 2p orbitals. Draw
each of these orbitals, with clear shading to indicate the mathematical sign of the
wavefunction. Label nodes.
2. Draw an energy diagram for the molecular orbitals for H2. Clearly label the σ and σ* orbitals
and fill in electrons as appropriate. Next, consider the addition of a single electron to H2 to
•–
form the radical anion [H2]
(this species has 3 electrons and an overall negative charge).
In which orbital does this additional electron reside? How will this reduction (addition of an
electron) affect the bond length and bond strength, relative to H2?
3. Label the hybridization of every atom (except hydrogen) in the following molecules. For two
of these compounds, describe the geometry of the molecule and associated orbitals using
clear illustrations.
O
H3C CH3
H3C
H 2C
C N
N
H
N
CH2
H2C C CH2
N
O
H 2N
N
H
N
4. Are the following compounds conjugated? If so, clearly indicate which p orbitals are involved
in the conjugated system.
NO2
OH
O
O
5. Draw reasonable resonance structures for the following molecules and reactive
intermediates. Clearly show electron movement with curved arrows.
OH
O
O
O
H
N
O
H
H
N3
H2C N N
N
H 2N
H
NH2
6. Problem 3.38 in Hornback
7. Predict which side of the equilibrium is favored for the following acid-base reactions. Explain
your reasoning.
O
OLi O
O
+
+
N
O
N
H
O
Li
H
N
+
NaH
ONa
+
OH
+
Li
H2
Na
N
HCl
O
S
+
+
NaCl
O
S
+
O
O
+
Li
NaNH2
+
Na
NH3
8. Explain the difference in pKa values for each set of compounds shown below. In your
answer, be sure to specify the most acidic proton.
A.
pKa =
C.
O
NH3
H2O
38
15.7
OH
O
B.
pKa =
D.
OH
O
O
OH
CH3SH
CH3OH
11
16
O
O
H3C
pKa =
OH
4.76
F3C
OH
- 0.25
O
pKa =
E.
3.7
H
pKa =
4.19
H
OH
F.
4.13
OH
CH3CH3
NO2
50
24
pKa =
10
7.15
9. Predict which is the stronger base for each pair of compounds shown below. Explain.
N
O
or
N
or
ONa
N
ONa
NH2
NH2
or
P
or
N
10. Propose a mechanism for the following reaction. Clearly show curved arrows for all electron
movement and briefly justify each step in your mechanism. Explain why the reaction is
favored or disfavored. How much sodium methoxide (NaOMe) is required for this reaction
(e.g. 1 equivalent, excess, a catalytic amount)?
O
NaOMe
MeOH
O
For additional practice, the following problems from the Hornback textbook are recommended.
You do not need to hand in solutions to these problems, but working through these exercises is
excellent practice for mastering the material and preparing for exams.
Chapter 3: 20, 21, 22, 23, 24, 26, 27, 28, 29, 31, 32, 34, 37, 38, 40
Chapter 4: 23, 24, 25, 26, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 46, 47