amines and amides Flashcards
what are amines?
If one or more of the hydrogens on ammonia is replaced with an organic group (e.g alkyl) then this is an amine
Primary= 1 hydrogen replaced
Secondary= 2 hydrogen replaced
Tertiary= 3 hydrogen replaced
What is formed if you replace add a 4th organic group to a tertiary amine?
A quartenary ammonium ion- joins with positive ions to form quarternary ammonium salts
What are surfactants?
Compounds which are partly soluble and partly insoluble in water
Cationic surfactants are positively charged, quarternary ammonium ions with at least one long hydrocarbon chain
Why are cationic surfactants useful in detergents?
The hydrocarbon chain is insoluble but will bind to non-polar substances (e.g. grease) whilst the positively charged head group is soluble in water so allows spots of grease to mix with water and be washed away
Why are cationic surfactants used in hair or fabric conditioners?
The positively charged part is attracted to the negative charge that hair or fabric pick up when they get wet. This forms a coating over the surface which prevents a buildup of static electricity
Why do amines act as weak bases?
They accept protons as the lone pair on the nitrogen atom will form a co-ordinate bond with the H+ ion.
What does the strength of the base depend on?
The availability of the lone pair on the nitrogen
Why are primary aromatic amines weak bases?
The benzene ring draws the electrons towards itself and the lone pair becomes partially delocalised onto the ring, so availability decreases
Why are primary aliphatic amines strong bases?
The alkyl groups push electrons onto attached group (inductive effect) so the electron density on the nitrogen increases and lone pair becomes more available
What are amides?
Derivatives of carboxylic acids with the functional group -CONH2
What are N-substituted amides?
Amides where one of the hydrogens on the nitrogen has been substituted with an alkyl group
How can we produce amines from halogenoalkanes?
By nucleophilic substitution, reacting halogenoalkane with ammonia. Forms a mix of primary, secondary, tertiary amines and quaternary ammonium salts as more than one hydrogen likely to be substituted
How do we form amines from nitriles?
Reduce a nitrile to an amine by using a strong reducing agent, such as LiAlH4 in dry ether followed by some dilute acid.
Why is LiAlH4 not used in industry?
Too expensive so industry uses a metal catalyst such as Pt or Ni at high temp and pressure- catalytic hydrogenation
How do acyl chlorides react with amines and ammonia?
Ammonia reacts to form amides and amines react to form N-substituted amides
Nucleophilic addition-elimination reactions
How are aromatic amines produced?
Reducing a nitro compound, e.g nitrobenzene
- Mix of nitrobenzene, tin metal and conc. HCl heated under reflux to make a salt
- Alkali, e.g NaOH, added to mixture to convert salt into an aromatic amine
What is a use of aromatic amines in industry?
Dyes
