Chemistry 312
Problem Set 3
(Due Friday, July 15, 2011)
1. Assign the following molecule to their appropriate
point groups
; also include a sketch
of the molecule that shows the
symmetry elements
for each molecule, justifying the
choice of point group.
a. CH
2
Cl
2
C
2v
b. BFClBr
C
s
c. NCCN
D
∞
h
d. 1,2,3trichlorobenzene
e. 1,2,4trichlorobenzene
f. ICl
4
–
D
4h
C
2v
C
s
g. adamantane (shown below – all four faces equivalent)
h. ferrocene
D
5d
(eclipsed = D
5h
)
T
d
2. Examine the D
4h
character table in resource section 4 in the textbook.
a. Give the term (Mulliken) symbol for the irreducible representation for which z is a
basis. Show, through a series of sketches, how the characters for the row that represents
the irreducible representation for which z is a basis.
The point group D
4h
has the symmetry operations E, C
4
, C
2
,
C
2
’, C
2
”, i, S
4
,
σ
h
,
σ
v
and
σ
d
.
The sketches should show what happens to the +z axis or a p
z
orbital under each of these
operations. For instance, E would leave the axis or orbital unchanged and thus would
have a character of +1; C
4
and C
2
would also leave it unchanged for a +1. On the other
hand, the perpendicular C
2
operations would both “flip” the axis or orbital, and they
would each have a character of –1, as would i, S
4
,
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 Summer '08
 Staff
 Mole, irreducible representation, symmetric stretching vibration, various quadratic functions

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