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20.4.1 Describe, using equations, the reactions of alcohols with carboxylic acids to form esters, and state the uses of esters. 20.4.2 Describe, using equations, the reactions of amines with carboxylic acids.
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20.4.1 Describe, using equations, the reactions of alcohols with carboxylic acids to form esters, and state the uses of esters. 20.4.2 Describe, using equations, the reactions of amines with carboxylic acids. 20.4.3 Deduce the structures of the polymers formed in the reactions of alcohols with carboxylic acids. 20.4.4 Deduce the structures of the polymers formed in the reactions of amines with carboxylic acids. 20.4.5 Outline the economic importance of condensation reactions. 20.4 Condensation Reactions
Condensation Reaction • Occurs when two molecules react to form a product with the loss of a small molecule. • Also called addition-elimination reactions • Responsible for: • Esterfication • Polymerization • Polyesters • Polyamides
Esterfication • Type of condensation reaction • Reaction of alcohol with carboxylic acid to make an ester and water. • Conditions: warming the mixture in the presence of concentrated H2SO4 catalyst. • Catalyst speeds up reaction and improves yield of the equilibrium
Two examples: • Ethanoic acid + methanol < -- > methyl ethanoate + water • CH3COOH + CH3OH < -- > CH3COOCH3 + H2O • So, the OH is taken from the carboxylic acid and the H is removed from the alcohol and combine to make H2O, then the two molecules combine where their bonds were broken 2.
Polyesters Are polymers of esters. Can form when the acid and the alcohol forming the ester has 2 functional groups each. All polymers are formed with the monomers (units) having 2 functional groups, which have active ends for linking together in a chain.
IB requires Can you recognize the repeating unit? Polyester formed (PET) from ethane-1,2-diol and benzene-1,4-dicarboxylic acid
Condensation reaction to form amides Carboxylic acid + primary amine secondary amide + water Ethanoic acid + methanamine methylethanamide + water CH3COOH + CH3NH2 CH3CONH(CH3) + H2O
Polyamides • Proteins are examples of polyamides. • Polymer that contains an amide link. • Synthetic polyamides are nylon and Kevlar. • Form when the monomers each have 2 functional groups. • One monomer has two –COOH groups (carboxylic acid) and the other monomer has two –NH2 groups (amine) • IB Required example: • 1,6-diaminohexane + hexanedioic acid producing 6,6-nylon (b/c its monomers each have 6 carbons)
Importance of condensation reactions We are very much dependant upon plastics, synthetic fibres such as nylon, kevlar... Commercial production of such materials has changed our world.
Sources http://www.elmhurst.edu/~chm/vchembook/402condensepolymers.html