6.2.1 & 2 -Amines, Amino acids, Amines & Chirality Flashcards
Naming when NH2 is attached to 1st C
- amine
e. g. hexylamine
Naming when NH2 is attached to middle C
no. where -NH2 is attached
amino
Longest carbon chain
e.g. 3 amino hexane
Naming when NH2 group is attached to 2/3 groups
N- side chain 1 N - side chain 2 - amine
e.g. N - ethyl, N methyl amine
alphabetical order
Primary amines
N attached to one R group, 2 H’s
Secondary amines
N attached to two R groups, 1 H
Tertiary amines
N attached to three R groups, no H’s
Quaternary ammonium salts
Not amines but ammonium salts with NO lone pair on the N
Aromatic amines
Have the N joined directly to the benzene ring
Bonding between amines
Some H bonding between molecules but weaker than in alcohols
No H bonding in 3’ amines
Many simple amines are liquids at rt
What does base strength of amines depend on
How well the N lone pair can accept H+
When is the basicity of an amine higher
When the charge density is higher
Base strength increases from ..
1’ to 3’ amines due to alkyl groups pushing electron density towards the N
Base strength of 4’ amines
Ammonium salts aren’t bases
Why is basicity low in aromatic amines
W/ aromatic amines, NH2 is an ED group so lone pair on N is drawn into delocalised ring, reducing electron density on lone pair
Highest to lowest basicity
3’ > 2’ > 1’ > NH3 > Aromatic
Synthesis of 1’ amines
Nucleophilic substitution
Excess ethanolic NH3 and haloalkane –> 1’ amine and NH4X
Synthesis of 4’ ammonium salts
Ethanolic NH3 and a large excess of the haloalkane
Explaining why something is the stronger base
X has a greater electron density on N lone pair as it is a 3’ /2’/ 1’amine
and therefore X has a greater ability to accept H+
Synthesis of 2’ amines
Excess haloalkane and 1’ amine
Neutralise w/ NaOH
Synthesis of 3’ amines
Excess haloalkane and 2’ amine
Neutralise w/ NaOH
Synthesis of aromatic amines
Nitrophenol + 6[H] —> phenylamine + 2 H2O
Sn - gets reduced
Conc. HCl
Large excess of haloalkane and amine –>
Ammonium salt
General formula of amino acids
RCH(NH2)COOH
What makes something an alpha-amino acid
Has both NH2 and COOH attached to same carbon (2nd)
beta amino acids
Have NH2 attached to 3rd carbon
Amino acids and acids
Ammonium salt
What allows amino acids to react w/ acids
NH2 is basic so can accept H+
Amino acids and strong bases
Carboxylate salt and water
Amino acids and carbonates
Carboxylate salt, water and CO2
What allows amino acids to react w/ bases
-COOH
Ester formation from amino acids
Amino acids + excess alcohol + H2SO4 —> ester w/ protonated amine group and alcohol replaced H in -OH on -COOH
Chiral centre
Tetrahedral
Carbon is attached to 4 DIFFERENT groups
2 optical isomers for each chiral centre
No double bonds
Which amino acid is achiral
Glycine
H2NCH2COOH
Enantiomers
Pair of stereoisomers which are NON-SUPERIMPOSABLE mirror images of each other
Racemic mixture
A 50:50 mixture of two enantiomers
Forming dipeptides
Condensation reaction
Loses OH from -COOH on one AA and H from -NH2 on the other AA
Drawing repeat units of polypeptides
Extend bonds and leave out H on -NH2 and OH on -COOH
Drawing 3D molecules
Wedged line - coming out of the plane
Dashed line - going into the plane
Tetrahedral - wedged, dashed, 2 straight
Amide group (peptide link)
CONH
Syntheisis of single optical isomers
Enzymes or bacteria
Chiral catalyst
Producing 1’/2’ amides from acyl chlorides
Acyl chloride + NH3/amine/amino acid
Acyl chloride and water
-COOH and HCl
