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Organic Chemistry - Polymers (Addition and Condensation polymerization)

Grade 11IGCSEChemistry

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Polymers are large molecules (macromolecules) built up from many small units called monomers through a process called polymerization.

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Addition polymerization occurs with unsaturated monomers (alkenes). The double bond C=CC=C breaks, allowing the monomers to join together in a long chain. Only one product is formed.

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The repeat unit of an addition polymer has the same atoms as the monomer but contains only single C−CC-C bonds.

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Condensation polymerization involves monomers with two functional groups. When they react, they link together and a small molecule (usually H2OH_2O or HClHCl) is eliminated.

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Polyesters (e.g., Terylene) are formed by the reaction between a dicarboxylic acid and a diol, creating ester linkages: −COO−-COO-.

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Polyamides (e.g., Nylon) are formed by the reaction between a dicarboxylic acid and a diamine, creating amide linkages (peptide bonds): −CONH−-CONH-.

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Addition polymers like poly(ethene) and PVCPVC are generally non-biodegradable because they are chemically inert, leading to environmental disposal issues.

📐Formulae

n(CH2=CH2)→−[CH2−CH2]n−n(CH_2=CH_2) \rightarrow -[CH_2-CH_2]_n-

n(CH2=CHCl)→−[CH2−CHCl]n−n(CH_2=CHCl) \rightarrow -[CH_2-CHCl]_n-

HO−R−OH+HOOC−R′−COOH→−[O−R−O−CO−R′−CO]n−+(2n−1)H2OHO-R-OH + HOOC-R'-COOH \rightarrow -[O-R-O-CO-R'-CO]_n- + (2n-1)H_2O

H2N−R−NH2+HOOC−R′−COOH→−[NH−R−NH−CO−R′−CO]n−+(2n−1)H2OH_2N-R-NH_2 + HOOC-R'-COOH \rightarrow -[NH-R-NH-CO-R'-CO]_n- + (2n-1)H_2O

💡Examples

Problem 1:

Draw the repeat unit for the addition polymer formed from propene, CH2=CHCH3CH_2=CHCH_3.

Solution:

−[CH2−CH(CH3)]−-[CH_2-CH(CH_3)]-

Explanation:

In addition polymerization, the double bond of the monomer CH2=CHCH3CH_2=CHCH_3 opens up. The methyl group (CH3CH_3) remains attached to the second carbon atom as a side chain, and the carbons form new single bonds to neighboring units.

Problem 2:

What are the two monomers required to synthesize the polyester Terylene?

Solution:

Ethane-1,2-diol (HO−CH2CH2−OHHO-CH_2CH_2-OH) and benzene-1,4-dicarboxylic acid (HOOC−C6H4−COOHHOOC-C_6H_4-COOH).

Explanation:

Terylene is a polyester formed via condensation polymerization. It requires a diol (alcohol with two −OH-OH groups) and a dicarboxylic acid (acid with two −COOH-COOH groups) to form repeating ester links.

Problem 3:

Identify the type of linkage found in Nylon and name the small molecule released during its formation.

Solution:

Amide linkage (−CONH−-CONH-); H2OH_2O is released.

Explanation:

Nylon is a polyamide. During the reaction between the amine group (−NH2-NH_2) and the carboxylic acid group (−COOH-COOH), a water molecule (H2OH_2O) is eliminated to form the amide bond.

Polymers (Addition and Condensation polymerization) Revision - Grade 11 Chemistry IGCSE