Kreidler, Kathy Thornridge High School

The student will
1. distinguish chiral objects from achiral objects.
2. apply the concept of chirality to a carbon compound.
3. define the term stereoisomer.

Apparatus Needed: 1. 6 to 8 ball and stick models, consisting of 1 black, 1 red, 1 orange, 1 yellow, and 1 green sphere and 4 connectors. Have two models made up as mirror images and leave the other models disassembled in zip loc bags. 2. mirror 3. baseball and baseball mitt 4. 2 sheets of polarizing film 5. sugar solution in shallow glass or plastic dish 6. caraway seeds 7. spearmint candy or gum Recommended Strategy: 1. Ask students to help set up models. 2. Have someone come up and try to make the models look alike by rotating the models without breaking any bonds. If all look alike, bring out the mirror image model and tell the students this is how you wanted it to look!
3. Introduce the term chiral. Give examples of other chiral
objects, such as shoes, gloves, hands, and feet.
4. Introduce the term stereoisomers.
5. One property of stereoisomers is that they rotate plane-polarized
light. This rotation can be effectively demonstrated on an
overhead projector by placing a shallow dish of sugar
solution between two sheets of polarizing film.
6. Relate chirality and the action of enzymes by showing how a
baseball mitt fits on only one hand.
7. Examples of biological significance:
One form may be a drug while the other form is ineffective.
(-)Adrenalin is a cardiac stimulant while the (+)form is
One form may be toxic while the other form is harmless.
One form may be an insect sex attractant while the other
form has no effect.
8. Conclude the lesson by passing out samples of caraway and
spearmint, which are stereoisomers which have noticeably
different odors.
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