Amino acids, amides, chirality Flashcards
What two functional groups do all amino acids have
What is the general formula for amino acids?
R-CH(NH2)-COOH (except from proline)
What are a-amino acids?
the amino and carboxyl groups are on the same carbon atom
how do you name amino acids?
amino…..acid
What are the functional groups on an amide?
an acidic carboxyl group and a basic amine group.
Treat each functional group as a separate reacting centre
What does the amine group react with?
The amine group is basic and can react with acids and become protonated.
H2N becomes H3N+ (+ion)
What does the carboxyl group react with?
The carboxyl group is acidic and can react with bases. The –COOH group is deprotonated.
H gets removed from cooh and h2o forms (COOH—>COO-)
What can the carboxylic function group react with?
alcohols in the presence of conc sulphuric acid to produce an ester.
O gets removed from OH and H gets removed from adjacent c to on one it’s on
h on cooh gets replaced by left over ch….
h2O formed
What is a peptide bond?
the specific name for the amide bond that forms when alpha amino
acids react
How do amino acids react together?
with the elimination of a water molecule to form a peptide (or amide) bond.
This is called a condensation reaction because a small molecule (water in
this case) is formed.
When two amino acids react together a dipeptide is made.
How are proteins and polypeptides formed?
by many condensation polymerisations involving the
loss of water.
What is a polypeptide?
a peptide containing more than 3 amino acid molecules (monomers)
What is a protein?
a chain of 40 or more amino acids linked together by peptide linkages
What must I do when drawing amino acids coming together by condensation reactions?
must start/end with NH2 or OH
what is hydrolysis?
This term means the splitting of water by reaction with another compound. It means the other compound also gets split.
If you split a protein you produce amino acids.
What does the hydrolysis of a protein require?
heating in aqueous acid or aqueous alkali conditions (in the body, enzymes are involved).
What happens in acid hydrolysis?
(+H2O + 2H+)
-bond splits between first Nh2 and o=
-o becomes oh
-both Nh2 become nh3+
-we get the protonated form of the amino group here
what happens in base hydrolysis?
-(+ 2NaOH)
-ONa gets added on the end of the 1st product
-NH becomes comes Nh2
-OH becomes ONa
+h2O
What does an amide look like?
-Amides are derived from carboxylic acids.
-In an amide the −OH part of the carboxyl group is replaced by an −NH2 group.
What is the gen form for amides?
O
||
RCHNH2
what is a primary amide?
n/amine group attached to one m carbon (1 R group)
What is a secondary amide?
n/amine group attached to two carbons (2 R groups)
What is a tertiary amide?
n/amine group attached to three carbons (3 R groups)
when do optical isomers exist?
when there is a chiral carbon atom; one with four different groups/atoms attached to it: the carbon atom is said to be asymmetrically substituted.
What does the chiral carbon atom in the molecule mean?
-that there are two non superimposable mirror image structures possible
-These are optical isomers of each other
(often known as enantiomers).
What are Diastereoisomers?
compounds with two chiral centres.
What are the reactions of amino acids?
amine group with acids
carboxyl group with bases
…..
