A2 - Unit 1 - Polymers and synthesis Flashcards
What is a peptide?
A compound made of amino acids linked by peptide bonds
How many different amino acids does the body have?
20
What is a zwitterion?
A dipolar ionic form of an amino acid that is formed by the donation of a hydrogen ion from the carboxyl group to the amino group.
Because both charges are present there is no overall charge
What is the isoelectric point?
The pH value at which the amino acid exists as a zwitterion
How does an amino acid react in acidic conditions?
The amino acid behaves as a base and accepts a proton from the acid
The amino acid forms a positively charged ion
How does an amino acid react in alkaline conditions?
The amino acid behaves as an acid and donates a proton to the base
The amino acid forms a negatively charged ion
What is a condensation reaction?
A reaction in which two small molecules react together to form a larger molecule with the elimination of a small molecule such as water
How do you carry out the acid hydrolysis of proteins?
Add water and 2H+ to the peptide, two positive ions are formed, with the H+ ions going to the lone pair on the nitrogen
How do you carry out the alkaline hydrolysis of proteins?
Add aqueous sodium hydroxide at 100 degrees
Amino acids split and take the form of their sodium salts
What are stereoisomers?
Species with the same structural formula but with a different arrangement of the atoms in space
What is a chiral carbon?
A carbon atom attached to four different atoms or group of atoms
What are optical isomers?
Stereoisomers that are non-superimposable mirror images of each other
Where does optical isomerism arise?
In organic molecules that contain a carbon atom attached to four different atoms or groups of atoms
What are the two common types of polyester?
- Polyesters made by reacting two different types of monomer units:
one monomer is a dicarboxylic acid with two COOH groups
one monomer is a diol with two OH groups - Polyesters made by reacting just one type of monomer unit containing COOH and OH groups
What is a repeat unit?
The specific arrangement of atoms that occurs in the structure over and over again. Repeat units are included in brackets, outside which is the letter n
What happens during condensation polymerisation from two types of monomer unit?
A bond forms between a hydroxyl group on the diol and a carboxyl group on a dicarboxylic acid
An ester linkage forms and water is eliminated
What happens during condensation polymerisation from one type of monomer unit?
A bond forms between the hydroxyl group on one lactic acid molecule and a carboxyl group on a different lactic acid molecule
An ester linkage forms, and water is eliminated
Give a property of poly(lactic acid) and give examples of what it is used for
It is biodegradable and there has been much recent interest in its use for food and drinks cartons
What are polyesters used for?
Making carpets, sports clothing and shirts.
Which functional groups make up the bonding regions of a polyamide?
A carboxyl group
An amine group
Give three examples of polyamides
Nylon-6,6
Kevlar
Proteins
What are the two types of polyamide?
- Polyamides made by reacting together two different types of monomer units:
One monomer is a dicarboxylic acid with two COOH groups
One monomer is a diamine with two NH2 groups - Polyamides made by reacting just one type of monomer unit containing both COOH and NH2 groups
Amino acids are this type of monomer, and polypeptides and proteins are this type of polyamide
What happens during the condensation polymerisation from two types of monomer unit?
A bond forms between an amine group on a diamine and a carboxyl group on a dicarboxylic acid
An amide linkage form and water is eliminated
If the monomer contains a double bond, what type of polymerisation is taking place?
Addition
If there are two monomer units, each with two functional groups what type of polymerisation is it?
Condensation
If there is one monomer with two different functional groups, what type of polymerisation is it?
Condensation
If the polymer contains ester or amide linkages, what type of polymerisation is it?
Condensation
If the backbone of the polymer is a continuous chain of carbon atoms, what type of polymerisation is it?
It is likely to be addition and the monomer will be an alkene
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
What happens in the alkaline hydrolysis of polyesters?
Hydrolysed by hot aqueous alkalis such as NaOH
Each ester linkage is hydrolysed to:
The sodium salt of a carboxylic acid -COO-Na+
A hydroxyl group -OH
What happens in the acid hydrolysis of polyesters?
Hydrolysed with hot aqueous acid, such as aqueous hydrochloric acid
Reaction is much slower than alkaline hydrolysis
Monomer units of the polyester are produced
What happens in the acid hydrolysis of polyamides?
Dicarboxylic acid is produced together with an ammonium salt of the diamine
What happens in the alkaline hydrolysis of polyamides?
In basic conditions the sodium salt of the dicarboxylic acid and the diamine are formed
What are the reagents to turn a halogenoalkane into an amine?
NH3/Ethanol
What are the reagents and conditions to turn a halogenoalkane into an alcohol?
NaOH/H2O
Reflux
What is the reagent to turn a secondary alcohol into a ketone?
K2Cr2O7/H+
What is the reagent to turn a ketone into a secondary alcohol?
NaBH4
What are the reagents and conditions to turn an alcohol into an ester?
Carboxylic acid/ H2SO4 catalyst
Reflux
What are the reagents and conditions to turn a primary alcohol into an aldehyde?
K2Cr2O7/H+
Distil
What is the reagent to turn an aldehyde into a primary alcohol?
NaBH4
What are the reagents and conditions to turn an aldehyde into a carboxylic acid?
K2Cr2O7/H+
Reflux
What are the reagents and condition to turn a carboxylic acid into an ester?
Alcohol/H2SO4 catalyst
Reflux
What is needed to turn an ester into a carboxylate and alcohol?
Alkaline hydrolysis
What is needed to turn an ester into a carboxylic acid and alcohol?
Acid hydrolysis
How do you add Cl on to benzene?
Cl2 / AlCl3
How do you add Br on to benzene?
Br2 / FeBr3
How do you add an NO2 group on to benzene?
Conc HNO3
Conc H2SO4
50 degrees
How do you make phenylamine from nitrobenzene?
Sn/conc HCl
Reflux
How do you make benzenediaonium chloride from phenlyamine?
NaNO2/HCl(aq)
<10 degrees
How do you make an azo dye from benzenediazonium chloride?
Phenol
NaOH
What is pharmacological activity?
The beneficial or adverse effects of a drug on living matter
What are the advantages of producing a single isomer with the correct pharmacological activity?
Risks from undesirable side effects are reduced
e.g. if thalidomide has been used as the ‘correct’ single isomer, morning sickness would have been prevented without the deformities caused by the other optical isomer
Drug doses are reduced
e.g. when a drug containing a mixture of two optical isomers is prescribed only half of the drug contains the isomer with the desired therapeutic effect, the other half is wasted
Give three examples of modern chiral synthesis
Using enzymes as biological catalysts
Chiral pool synthesis
Use of transition element complexes
How are enzymes being used as biological catalysts to synthesise chiral isomers?
Nature is good at making single optical isomers. If the synthetic route can be designed using enzymes, then a single isomer can be produced
Drug manufacturers can use purified enzymes or enzyme containing microorganisms to biocatalyse any reaction step that produces a chiral carbon
