Importance of Functional Groups in the Synthesis of Polymers

1. Importance of Functional Groups in the Synthesis of Polymers Indicators C-3.5 and C-3.7 South Carolina Science Standards Chemistry Section

2. Nylon SynthesisExample of a step reaction The reaction illustrated here has been simplified and is just one of many methods for synthesizing nylon. The actual reaction has many more steps. sebacoyl dichloride (decanedioyl dichloride) This is the same thing as 1,10-dichloro-1,10-decan-1,10-dial for which you wrote a structural formula in the prelab quiz carbonyl group alkyl halide group (chloro- group) amine group Pay close attention to how the reaction takes place between the functional groups. In this case the reaction occurs between an amine group and a carbonyl group. 1,6-hexandiamine This is the same thing as hexane-1,6-diamine for which you wrote a structural formula in the prelab quiz An alkyl halide group (a chloro- group) is also attached to the same carbon that is part of the carbonyl group.

3. Notice also that the reaction is NOT taking place between the hydrocarbon groups in the parent chains or between the hydrocarbon groups and functional groups. sebacoyl dichloride (decanedioyl dichloride) This is the same thing as the 1,10-dichloro-1,10-didecanal for which you wrote a structural formula in the prelab quiz hydrocarbon parent chain hydrocarbon parent chain 1,6-hexandiamine This is the same thing as Hexane-1,6-diamine for which you wrote a structural formula in the prelab quiz The reaction IS taking place between functional groups.

4. sebacoyl dichloride (decanedioyl dichloride) This is the same thing as the 1,10-dichloro-1,10-didecanal for which you wrote a structural formula in the prelab quiz 1,6-hexandiamine This is the same thing as Hexane-1,6-diamine for which you wrote a structural formula in the prelab quiz

5. + sebacoyl dichloride (decanedioyl dichloride) This is the same thing as the 1,10-dichloro-1,10-didecanal for which you wrote a structural formula in the prelab quiz + 1,6-hexandiamine This is the same thing as Hexane-1,6-diamine for which you wrote a structural formula in the prelab quiz

6. + This kind of polymerization reaction in which molecular growth occurs due to the interaction of functional groups is called step growth polymerization. Another term for this class of reaction is condensation polymerization. The term condensation refers to the production of the small byproduct; HCl. sebacoyl dichloride (decanedioyl dichloride) covalent bond 1,6-hexandiamine The byproduct of THIS reaction is hydrochloric acid (HCl). Other step reactions produce different byproducts. Note: You will learn more about reversible reactions in the equilibrium unit later in the semester. HCl must be removed from the reaction container to prevent decomposition (a reverse reaction).

7. Polymerization is not just one reaction between two molecules. The reaction continues to covalently bond molecules together into really long chains. H+ + Cl Notice—again—how the reactions are all taking place at the functional groups and NOT at the hydrocarbon groups.

8. 6 carbon chain 8 carbon chain repeat unit The repeating unit in the polymer is usually indicated in this manner. A polymer such as this one which was synthesized from 2 different monomers is called a copolymer. This polymer is called nylon. There are different forms of nylon. This particular form is called nylon 6, 8 due to the number of carbon atoms in the 2 copolymer parts of the repeat unit.

9. The long chains have a weak (side-to-side) attractions to each other. Because there are so many of them, however, the combination of these bonds is quite strong. The weak(side-to-side) attraction is called hydrogen bonding. The hydrogen bonds are NOT the same as covalent bonds. These hydrogen bonds are illustrated here as 3 dashed lines. Note: This is the same kind of attraction that holds the 2 sides of DNA together.

10. PET SynthesisExample of a step growth polymerization dimethyl isophthalate hydroxyl or alcohol functional groups ester functional groups ethylene glycol Guess where the reaction will take place?

11. PET SynthesisExample of a step growth polymerization dimethyl isophthalate esterification ethylene glycol A catalyst of some kind is needed to make this reaction occur.

12. Remember that this kind of polymerization reaction with more than one monomer and a byproduct is called a step growth reaction or condensation reaction. methanol byproduct ester group The byproduct of THIS reaction is methanol (CH3OH). Methanol must be removed from the reaction container to prevent decomposition (a reverse reaction).

13. x methanol byproduct: A methanol molecule is formed every time an ester linkage is formed. repeat unit

14. This kind of polymer is called a polyester because the copolymers—dimethyl isophthalate and ethylene glycol—form an ester linkage. Through the structure, the ester is the highest priority functional group and it repeats itself over and over. polyethylene terephthalate PET ester group repeat unit

15. CH2 CH2 CH2 CH2 Polyethelene SynthesisExample of chain growth polymerization ethylene (ethene) Pay close attention to how the reaction takes place between the functional groups. In this case the reaction occurs between alkenyl groups (i.e. between double bonds). A catalyst of some kind is needed to make this reaction occur.

16. CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2

17. This kind of polymerization reaction which has just one type of monomer is called a chain reaction. An older term for this class of reaction is a addition reaction.

18. Polymer Synthesis The BIG IDEA! • From this activity… • You are NOT expected to understand all the intricacies of polymer synthesis. • You ARE expected to understand from this activity that FUNCTIONAL GROUPS are the locations where reactions take place in organic chemical reactions.

19. The End