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CHM 504
Midterm Examination 2 (repeat)
Trimester 2, 2014.
ANSWERS
1.
Write down the IUPAC names of the following molecules.
[9 marks]
2.
Define or explain the following terms.
(a) Diastereomers
Stereoisomers which are not mirror images of each other.
(b) Optical activity
The ability of a molecule to rotate the plane of plane-polarised light.
3.
For each of the molecules shown below, CLEARLY draw an asterisk next to each
stereocentre. Then indicate under each molecule whether it is CHIRAL or ACHIRAL.
chiral
achiral
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chiral
4.
For each of the molecules shown below, indicate on the diagram itself, in the space provided
next to each group attached to the stereocentre, its priority, by writing the numbers 1, 2, 3, or
4 (1 being the highest and 4 the lowest priority). Then indicate whether the configuration of
the stereocentre is R or S.
S
5.
R
What reagents would you use to accomplish each of the transformations shown below?
[6 marks]
6.
The specific rotation of cholesterol, []D = – 31.5o. If a sample of cholesterol is dissolved in
chloroform at a concentration, c = 0.15 g cm-3, placed in a sample tube of length, l = 1.00
dm, and its optical activity measured in a polarimeter using the usual sodium D light, by
what angle  would the plane of polarised light be rotated?
= – 31.5o x 1.00 x 0.15 = – 4.7o
7.
Write down the mechanism of the following reaction. Draw any intermediates, and use
curved arrows to show the movement of electron pairs in the breaking or forming of bonds.
Page 2
8.
Draw the major organic product of each of the following reactions. Where relevant, give the
correct isomer or stereoisomer.
Page 3