Amino acids (48)
At an α
amino acid's isoelectric point, it becaomes a zwitterion. A H
If the amino acid is in a solution more alkaline than it's isoelectric point, it acts as a acid, it donates a proton from the NH3 group.
In this example, the isoelectric point is pH 7
Polypeptides and proteins (50)
Polypeptides and proteins are long chains of amino acids.
These are formed by the OH group on one amino acid and a H off the N on the other, leaving to form a water molecule, and the C and the N form a peptide bond.
Because water is given out, this a condesation reaction, to split the chain up, it is a hydrolysis reaction.
Optical Isomerism (52)
Steroismers are species with the same structural formula but a different arrengement of atoms in space.
Optical isomers are steroismers that are non-superimposible mirror images of each other.
The two types of stereoisomerism are cis/trans and E/Z. It's cis/trans if there is a hydrogen on each carbon, E/Z is used if the groups have different molecular masses.
A chiral carbon is a carbon attached two four different groups, all amino acids have a chiral carbon execpt glycine (R-group = H).
Condensation polymerisation - polyesters (54)
Polyesters are made via condesation reactions, like the proteins were.
There are three main types:
1. A chain formed from two different types of monomer unit, a diol (alcohol group on each end) and a dicarboxillic acid (with two -COOH groups).
2. Or a chain formed from one diol monomer
3. Or formed from one monomer, with two groups, a COOH and a OH.
You just remove an OH from one and a H from the other and join the places where you took them from together.
Polyesters are used to make fibres.
Condensation polymerisation - polyamides (56)
These are made by removing a water molecule, and we're still on condensation reactions.
You take the OH off the COOH again, and a H off the NH2 (getting the hang of this yet?)
There are two ways of making polyamides:
1. Two monomers, a diamide (two amine groups) and a dicarboxillic acid (have a guess!)
2.One monomer with a carboxillic acid group and a amine group.
Polyamides are used to make fibres. Kevlar and Nylon are polyamides.
This was in AS chemistry, but they still may ask you about it on the exam, basically, just lose the double bond and join it all together.
Lose a small molecule such as water or hydrochloric acid (although anything but water is very unlikely to come up) and join the spare bonds together.
Breaking down condesation polymers (60)
Hydrolysis is used to split up condensation polymers:
Base Hydrolysis NaOH/H2O
In polyesters, the functional groups split up and change into COO
NA and NH2.
Acid Hydrolysis H2O/H+
In polyesters, the functional groups split up and change into COOH and OH. In polyamides, the functional groups split up and change into COOH and NH2.