[CHEM] Chapter 11.6 - Macromolecules

1 DARRELL ER (COPYRIGHTED) © TOPIC 11.6: MACROMOLECULES DARRELL ER (COPYRIGHTED) ©

2 CHAPTER ANALYSIS THE ABOUT MASTERY EXAM WEIGHTAGE • Key component of Organic Chemistry • Commonly tested, especially Section A & B • Know how the difference between ‘Addition Polymerisation’ & ‘Condensation Polymerisation’ • Know your ester linkage & amide linkage • Heavy overall weightage • Entire Organic Chemistry portion accounts for 15- 20% of each year’s Chemistry paper DARRELL ER (COPYRIGHTED) ©

3 MACROMOLECULES POLYMERISATION ADDITION POLYMERISATION CONDENSATION POLYMERISATION KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

4 MACROMOLECULES A macromolecule is a large molecule that is formed from many smaller molecules. Different macromolecules usually contains different smaller units and linkages. DARRELL ER (COPYRIGHTED) © POLYMERISATION When polymerisation occurs, small molecules known as monomers are linked together to form a long-chain macromolecule known as a polymer. Polymerisation is defined as the process where small molecules (monomers) chemically combined together to form one large chainlike molecule (polymer). The repeating unit of a polymer is the smallest portion of the polymer, that when repeated multiple times, would form the entire polymer.

5 POLY(ETHENE) Poly(ethene) is an example of a polymer that is formed using addition polymerisation of ethene monomers. During addition polymerisation, the C=C double bond is broken. The equation for the addition polymerisation of ethene monomers to form poly(ethene) is: n(CH2 = CH2)  -(- CH2 - CH2 -)-n The repeating unit of poly(ethene) is: ADDITION POLYMERISATION DARRELL ER (COPYRIGHTED) © ADDITION POLYMERISATION Addition polymerisation is the process where small molecules (monomers) are linked together to form a polymer without any other by-products. APPLICATION Poly(ethene) is the most widely used plastic because of its resistance to many different chemicals, and that it is not soluble in water at room temperature. It is present in plastic products such as plastic bags, plastic bottles and used as water pipes.

6 NYLON Nylon is a synthetic polymer formed through condensation polymerisation of dicarboxylic acid and diamine, one containing the carboxylic acid functional group and the other containing the amine functional group. During the condensation reaction process, water molecules are formed as by-products and removed: Nylon is light, strong, and has high stretchable. Hence, this man- made fibre is used to make clothing, fishing lines, parachutes and sleeping bags. CONDENSATION POLYMERISATION DARRELL ER (COPYRIGHTED) © CONDENSATION POLYMERISATION Condensation polymerisation is the process where two different monomers are chemically combined to form a polymer. The process produces by-products such as water. The repeat unit of nylon contains the -CONH- amide linkage. The polymer is made up of monomers linked by the amide linkages, hence it’s called polyamide.

7 TERYLENE Terylene is a polymer formed through condensation polymerisation of dicarboxylic acid and diol, one containing the carboxylic acid functional group and the other containing the alcohol functional group. During the condensation reaction process, water molecules are formed as by-products and removed: Man-made fibres like terylene lasts longer, would not decompose, and has the ability to maintain their shape under humid conditions. Some uses of terylene are also used to make sails of boats and clothes. CONDENSATION POLYMERISATION DARRELL ER (COPYRIGHTED) © CONDENSATION POLYMERISATION Condensation polymerisation is the process where two different monomers are chemically combined to form a polymer. The process produces by-products such as water. The repeat unit of terylene contains the -CONH- ester linkage. The polymer is made up of monomers linked by the ester linkages, hence it’s called polyester. O

8 SUMMARY DARRELL ER (COPYRIGHTED) © Addition polymerisation Condensation polymerisation Monomers must contain a double bond (e.g. alkenes) Monomers must have two functional groups at the two ends No by-products is produced By-products like water are produced Example: polyethene Example: nylon & terylene

ALL ORGANIC COMPOUNDS Complete Combustion Incomplete Combustion ALKANE ALKENE ALCOHOL CARBOXYLIC ACID C - C Prefix Meth- 1 Eth- 2 Prop- 3 But- 4 Pent- 5 Hex- 6 Hep- 7 Oct- 8 Non- 9 Dec- 10 Catalytic Cracking (Al2O3 & SiO2, 600 °C) X + O2 (g) → CO2 (g) + 2H2O (l) CH4 (g) + Br2 (g) → CH3Br (g) + HBr (g) Substitution (UV light) Hydrogenation (200 °C & nickel) Bromination (Test for C=C bonds) Hydration (300 °C & 60 atm, Phosphoric(V) acid) LONG CHAIN ALKANE Addition Polymerisation (High temp & pressure) H2 gas (For Haber process) Fermentation (37°C, yeast & no O2) SUGAR C6H12O6 → 2 C2H5OH + 2 CO2 C = C -OH Oxidation (acidified aqueous potassium manganate(VII) / exposed to air) Esterification (warm, sulfuric acid) ESTER + H2O -COOH -COO- Condensation Polymerisation (elimination of water) C2H4 (g) + Br2 (aq) → C2H4Br2 (aq) DARRELL ER (COPYRIGHTED) © DARRELL ER (COPYRIGHTED) © X + O2 (g) → CO (g) + 2H2O (l) POLYMER O

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