Summer Research Program for Science Teachers
Paul Englehart
Syosset High School, Long Island
Understanding of the Structure of an Amino Group
Class: Honors Chemistry
Objectives:
1. To review the structural characteristics of Bronsted-Lowry acids and bases.
2. To have students develop an understanding of the structure of an amino group.
3. To have students compare the structures of amines to ammonia.
4. To review the structural characteristics of an amino acid. [9-12 Content Standard B- Structure and properties of matter]
5. To have students apply the properties of amino and carboxyl groups to the formation of an amino acid zwitterion. [9-12 Content Standard B- Chemical reactions]
6. (Time permitting) To develop the concept of polymerization from dehydration synthesis of peptides.
Materials: large molecular model kit [Content Standard Unifying Concepts- Models and explanation] [Teaching Standard D- Make accessible science tools]
Plan:
1. Make molecular models of ammonia, methylamine, ethylamine, dimethylamine, trimethylamine, acetic (ethanoic) acid, and a general amino acid.
2. With the ammonia model, have the students explain why this molecule can act as a B-L base.
3. Have a student show the interaction of the ammonia model with the acetic acid model.
4. Have a different student explain why the acetic acid molecule can act as a B-L acid.
5. Show the methyl amine molecule and have students predict its chemical behavior. [9-12 Content Standard A- Analyze alternative models and explanations]
6. Repeat this discussion with the other amine models. [Teaching Standard B- Orchestrate scientific discourse]
7. Define the amino group and primary amine, secondary amine and tertiary amine.
8. Have the students develop the structure of an amino acid.
9. Develop the possibility of interaction between the amino group and carboxyl group on the same molecule, i.e., the formation of a zwitterion.
10. Have the students review the interaction of one amino acid molecule for another (the model they developed and your "premade" model), i.e., the formation of a peptide bond.
11. Define "polymer" and "condensation polymerization".
12. Have students relate other biochemical reactions from their Biology class to polymerization, e.g., polysaccharides.
[Teaching Standard A- Work across disciplines]
Follow up: the next class period
should be used to discuss addition polymerization and free
radicals. Termination of polymerization can also be discussed and
comparisons to esterification can be made.