F324 - Polymers And Synthesis
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What is the general formula of an amino acid?
RCH(NH2)COOH
What is a peptide?
A compound made of amino acids linked by peptide bonds.
What is a zwitterion?
An internal salt that exists at the isoelectric point. A dipole ionic form of an amino acid that is formed by the donated of a hydrogen ion from the carboxyl group to the amino group. Because both charges are present, there is no over all charge.
Describe the isoelectric point.
The pH value at which the amino acid exists as a zwitterion. Different point for each different R group.
What does amphoteric mean?
Can react with both acids and bases.
Describe how an amino acid reacts to different pH values.
If the pH is more acidic than the isoelectric point: Behaves as a base and accepts a proton at the O- to become OH, positively charged. If the pH is more alkaline than the isoelectric point: Acts as an acid and donate a proton from the NH3+ group to become NH2. Negatively charged, also forms water.
What is a condensation reaction?
One in which two small molecules react together to form a larger molecule with the elimination of a small molecule such as water.
What is a protein?
A long chain of amino acids joined together by peptide linkages.
What is hydrolysis?
The breaking of a bond by reaction with water, it can be catalysed by acid or alkali.
Describe acid hydrolysis.
Forms positively charged amino acids because of the H+ ions preset in the acid. Heated under reflux with HCl
Describe alkali hydrolysis.
Aqueous NaOH at 100*c. Forms a sodium salt and adds a H to one Page 51
What are stereoisomers?
Species with the same structural formula but with a different arrangement if the atoms in space.
What is a chiral carbon?
A carbon atom attached to four different atoms or groups of atoms.
What are optical isomers?
Stereoisomer that are non superimposable mirror images of each other about an organic chiral centre.
What is the main use of polyesters?
Fibres in clothing.
Describe the formation of terylene.
n Ethane-1,2-diol + n Benzene-1,4-dicarboxylic acid —> (terylene)n + (2n-1) H2O String fibre for carpets and clothing. Page 55
What is the repeat unit?
The specific arrangement of atoms that occurs in the structure repeatedly.
Describe the formation of poly(lactic acid).
One monomer of lactic acid (2-hydroxypropanoic acid) Biodegradable so used for food and drink cartons.
Describe the formation of nylon-6,6
1,6-diaminohexane + Hexane-1,4-dioic acid Used to make balloon fabric Page 57
Describe the oration of Kevlar.
Benzene-1,4-dioic acid + Benzene-1,4-diamine Protective clothing, fire resistant, strong. Bullet proof vest.
What is a biodegradable polymer?
A polymer that breaks down completely into carbon dioxide and water.
What is a degradable polymer?
A polymer that breaks down into smaller fragments when exposed to light, heat or moisture.
Describe the hydrolysis of polyesters.
Base hydrolysis: Hot aqueous NaOH Forms the sodium salt of the carboxylic acid. Acid hydrolysis: Aqueous HCl Slower than base Monomer units are produced
Describe the hydrolysis of polyamides.
Base hydrolysis: Hot aqueous NaOH Sodium salt of the dicarboxylic acid and the diamine are formed. Acid hydrolysis: Hot aqueous HCl Positive diammonium salt and the dicarboxylic acid are formed. Page 60