A

1
What is the best term to describe the
relationship between A and each of the other
molecules?
Constitutional isomers? Conformations? Enantiomers
? Diastereomers? Identical?
B
E
C
F
A
Are any of these molecules optically active?
D
G
2
same
The two dot structures for B are the same thing.
When turned over, dots reverse!
B
E
.
.
turn over
turned over
.
.
turned over
.
.
.
.
.
C
F
same
.
.
.
A
turned over
same
same
.
.
.
D
.
Some structures (C,D,E) have to be turned over
or they would have no dots (!) which is
meaningless.
.
G
turned over
Dot Structures reveal which ones are the same
molecule, but do not give conformations.
Different conformations give the same dot
structure.
3
ANSWERS
A-C and E are all the same constitutional isomer,
1,3,5-trichloro- ,
but F is 1,2,4-trichloro-

• F is a constitutional isomer to A and to any of
  the others.
• A (e,e,a) and B (a,a,e) are conformations
• A (e,e,a) and C (e,e,e) are diastereomers
• A and D are diastereomers (D is a conformation
  of C)
• A and E are diastereomers (E is identical to D,
  turned left-to-right)
• A and G are identical (G is the same as A turned
  left-to-right)

Only F is optically active, all the rest are meso
molecules!
aD 0
aD 0
4
Planes of Symmetry Some of them have three
planes of symmetry!
B
E
.
.
turn over
.
.
.
.
.
.
.
C
F
.
.
.
A
no planes
.
.
.
D
.
.
G
All are meso except F