Figure 4-164. Structures of Kevlar® and Nomex®.
A brief remark is due concerning the terminology used for the C(O)-NH bond. This bond is sometimes called a peptide bond and sometimes an amide bond. Both names are correct. For a biochemist dealing with proteins, the C(O)-NH bond is a peptide bond. Polymer chemists call this bond an amide bond. Polymers based on the amide bond are called polyamides
. Both types of nylon, Kevlar®, and Nomex® are polyamides. 4.9.6. Exercises.
1. Draw chemical structures of (a) pentylamine; (b) dimethylbutylamine; (c) methylethylammonium chloride; (d) aniline; (e) phenylammonium bromide; (f) 3-aminopentanoic acid; (g) 2-methyl-3-aminobutanoic acid.
2. Are ethylamine, diethylamine, and triethylamine stronger bases than ammonia? Answer
3. Place ammonia, trimethylamine, dimethylamine, methylamine, and aniline in the order of decreasing basicity. Answer
4. Write a balanced chemical equation for the full combustion of propylamine. Answer
5. You have benzene, nitric acid, sulfuric acid, and sodium sulfide. How can aniline be made using these chemicals? Answer
6. Which of the following compounds are chiral? (a) dichlorobromomethane; (b) 3-aminobutanoic acid; (c) 4-aminobutanoic acid; (d) bromochlorofluoroiodomethane; (e) bromochlorofluoromethane; (f) isopropanol; (g) acetone; (h) 3-methylhexane; (i) 3-methyl-1-pentene. Hint
7. For each chiral compound identified in Exercise 6 above, sketch 3-dimensional structures of both enantiomers using wedge and dash notation to illustrate that one is a mirror image of the other.
8. Draw a chemical scheme for the formation of the alanine inner salt (zwitterion) from alanine. Hint
9. Write chemical equations for reactions of alanine with (a) HBr and (b) KOH. Hint
10. Draw chemical formulas for nylon 6.6 and nylon 6 and schemes for their formation from the corresponding monomers. [Answer: Figures 4-161 and 4-162]
11. Explain why catalytic rather than stoichiometric amounts of water are used to make nylon 6 from caprolactam. Answer
12. Review the structures of Kevlar® and Nomex® (Figure 4-164) and figure out what monomers are used to make both polyamides. Draw the structures of, and provide chemical names for, the monomers.