6D - Amines, amides & polyamides Flashcards
Define Amine
Amine = A NH3 group where one or more of the Hs have been substituted with an alkyl group
Structure of a primary, secondary and tertiary amine.
How many alkyl groups does each have?
Define:
Aliphatic amine
Aromatic amine
Aliphatic amine = Nitrogen atom attached to at least one branched carbon chain
Aromatic amine = Nitrogen atom attached to an aromatic ring
Name + clssify what type of amine this this
Ethylamine
Primary amine
Name + clssify what type of amine this this
2-Aminopropane
Secondary amine
Name + clssify what type of amine this this
Ethane-1,2-diamine
Primary amine
Name + clssify what type of amine this this
Phenylamine
Name + clssify what type of amine this this
N-methylpropylamine
N is for the shorter alkyl chain present when it’s a seondary amine
Name + clssify what type of amine this this
Triethylamine
Tertiary amine
What intermolecuar forces are present in amines?
Mainly - most important:
- London forces
- Hydrogen bonding
Also has permanent dipole-dipole interactions
Strength in london forces in relation to the size of the amine?
Larger amine, no’ of electrons increase ∴ stronger longer forces but compromise the H bonding in secondary & tertiary structures.
- Increased branching reduces SA available for H bonds to form
Question:
Compare boiling points
- Decreases from primary → secondary → tertiary
- Diethylamine = lowest as most branches ∴ weakest london forces out of the 3
- 1-aminobutane = highest as longest alkyl group ∴ increases the size of the moledule, least branches ∴s strongest london forces ∴ highest boiling point
Trend of solubility of amines
Gets less solution as the amine increases in size - alkyl group increases, they’re hydrophobic. Small ainesa re very solution in water
Why can amines act as bases?
- Ammonia molecule can accept a proton because N has a lone pair that can donate H+ to form a sative covalent bond
NH3 + H+ ⇌ NH4+
Amine + Acid → Alkylammonium salt
Amine + Acid → ?
Amine + Acid → Alkylammonium salt
Draw the structure of the alkylammonium ion
What do amines smell like?
Theie volatility?
Relatively voltalile
Smell FISHY
2 ways of preparing primary amine
Reagents + conditions
Method 1:
Nitrile + H2 → Amine
R = Nitrile
C = Nickle catalyst
Method 2:
- Haloalkane / RX + Ammonia → Ammonium salt w/ X halogen
- Ammonium salt + NaOH → Primary amine + NaX + H2O
R = NH3, haloalkanes
C = 1. Excess ammonia is used to prevent further substitution of amine group to form secondary / tertiary amines. 2. Ethanol as solvent to prevent any substitution of the H2O to produce alcohols
Producing secondary / tertiary amines
Reagents + conditions
- Primary amine + Haloalkane → Dialkylammoniumm salt
- Dialkylammoniumm salt + NaOH → Secondary amine + NaX + H2O
Tertiary amines are just a further loop of the reaction with secondary amines
Preperation of aromatic amines
Reagents + conditions
Reduction of nitrobenzene gives aromatic amine:
Nitrobenzene + H2 → Aromatic amine + H2O
R = Tin(Sn) and conc HCl to act as a reducing agent
C = Ecess NaOH(aq), heat under reflux
Give the structure of an amino acid
Define alpha amino acid
Alpha amino acid = Amine group attached to alpha carbon (2nd carbon atom) which is next to a carboxyl group
Amine group of amino acid + Acid → ?
Amine group of amino acid + Acid → Ammonium salt
Carboxyl group + aqueous alkali → ?
Carboxyl group + aqueous alkali → Salt + Water
Carboxyl group of amino acid + Alcohol group → ?
Reagents + conditions
Esterification
Carboxyl group of amino acid + Alcohol group → Ester + Water
R = Amino acid, alcohol
C = Small amounts of H2SO4 and one excess alcohol
Define isoelectric point
Isoelectric point = Point at which the zwitterion forms
Define zwitterion
Zwitterion = Point at which the amino acid has no overall charge because it contains both positively / negatively chagred groups
Give the structure of primary, secondary and tertiary amides
Define optical isomers
Optical isomers = 2 non-superimposable mirror images of a molecule as a result og having a chial atom
Name the one amino acid that doesn’t exhibit optical isomerism
Glycine
What are a pair of enantiomers?
They’re a pair of optical isomers
Show that amino acids have a chiral carbon
Define addition polymer
Addition polymer = Formation of a very long molecule chain, by repeating addition reactions of unsaturated small monomers
Define condensation polymer
Condensation polymer = Formation of a very long molecule chain by the joining of monomer(s) together in which H2O is lost
2 ways to make polyamides = ?
Method 1:
Dicarboxylic acid + Diamine → polyamide + H2O
Method 2:
Molecule that contains both a carboxyl group and amine group
Give 2 example of polyamides used in real life + what are their uses
Nylon 6,6:
It’s very strong ∴ useful for:
- making ropes, fishing nets and fabrics
Normex:
Synthetic heat + fire retardant polymer.
Used in oven gloves and fire protective wear worn by formula 1 racing drivers and pit crew
What does the 6,6 refer to in nylon 6,6?
The number of carbons present in the diamine and dicarboxylic acid
Acid hydrolysis of polyamides
Reagents + conditions + products
Polyamide + H2O ⇌ Dicarboxylic acid + Dialkylammonium salt
R = Dilute aqueous acid (H+) catalyst, H2O
C = Heat under reflux
REVERSIBLE
Base hydrolysis of polyamides
Reagents + conditions + products
Polyamide → Dicarboxylate salt + Diamine
R = OH-(aq) ions, H2O
C = Heat under reflux
NOT REVERSIBLE
