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Chemistry Mrs Taylor

Polyesters and Polyamides

Di-Carboxylic + Di-ol (one alcohol either end) -> Ester

OH from Carboxylic Acid

COOH-(benzene)-CO OH + HO-CH2-CH2-OH (removed)

PolyamidesPolyamides are made from a carboxylic acid and an amine so to make a polyamide we need a di-carboxylic acid and a di-ol

For example nylon 6-6 (6 comes from number of carbons).

HO=C-CH + COOH +H2NCH2CH2CH2CH2CH2NH2

[OC- -C-O-CH2-CH2-O] = O

[O-C-CH2CH2CH2-C-N-CH2CH2CH2CH2-N] = O H -

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COOH-

CH2 5= H2 ->

e e

g U

+ H2O

Am i Ac id Amin e g and carbox y ic acid group

Po ss ible for primar y, sec ondar y, tertiar y and quat ernar y

All Amino a cids ha ve Chiral carbon s (Except Gl ycine Amino A cids ha ve a carbox ylic acid group and anamin e group. Th ey exhibit opti calisom erism a s th ey ha ve chiralcentr es/ Chiral carbon s.

Anphat eric Can a ct lik e an a cid or

a ba se .

[C-(CH2 5- H] = O

2 Amino

What eve rthatbran ch is.

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Amino acids have anphoteric properties I.E. they can act like an acid or a base.

I.E.

Acid = a proton donor

Base = a Proton Acceptor

Zwitter Ion A molecule with a positive and a ne ative char e (Di-Polar) usually due to electrone ativity. So overall Neutral

Like an ionic Salt

Properties of Zwitter Ion:Hi h Meltin Point ( Lattice Structure)

Conducts electricity when I liquid form

Dissolve in water

They form ionic bonds with each other

A dding an a c id to an A mino Ac id SolutionIn Acids Amino Acids (Zwitter ions only) act as a base so they will accept a proton and have astructure like this:

A dding an alkali to an amino a c id solutionIn an Alkali Amino Acids (Zwitter Ions only) acts as an acid so they will donate protons and have astructure like this:

If you increase the pH of a solution of an amino acid by addin hydroxide ions the hydro en ion isremoved from the -NH 3

+ roup.

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Peptides and polypeptidesAmino Acids can join to ether to form bi er molecules ! if two join to ether we call it a di-peptide ! if three join to ether we call it a tri-peptide and when many join to ether its called a polypeptide.

OR

In each case ! the linka e shown in blue in the structure of the di-peptide is known as a peptide link.In chemistry ! this would also be known as an amide link ! but since we are now in the realms of biochemistry and biolo y! we'll use their terms.

If you joined three amino acids to ether ! you would et a tri-peptide. If you joined lots and lotsto ether (as in a protein chain) ! you et a polypeptide. When an Amino Acid joins a Poly-petideCondensation polymerisation takes place. (do the repeatin unit the same with a n outside thebrackets).

A mino Ac id ProteinsProteins are lon poly-peptide chains ! The primary structure is the sequence of the amino acids ! thesecondary structure will be the arran ement of the chains ! this is due to hydro en bondin and willbe an Alpha Helix or a beta pleated sheet.

With an amide like ethanamide ! the carbon-nitro en bond in the amide roup is broken and you eta carboxylic acid formed:

Now imagine doing the same thing with a simple dipeptide made of any two amino acids.

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Mixtures of Amino Acids can be separated and identified by paper or thin layer chromato " raphy.

Proteins and condensation polymers under " o hydrolysis # they will break down to form the aminoacids or molecules they started with. For Hydrolysis to occur a stron " acid and specific enzymecatalyst is needed.