Amines
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What are the base properties on prmary aliphatic amines
act as Bronsted-Lowry bases because the lone pair of electrons on the nitrogen is readily available for forming a dative covalent bond with a H+ and so accepting a proton.
Why are primary akiphatic amines stronger than ammonia
As the alkyl groups are electron releasing and push electrons towards the nitrogen atom and so making the lone pair of electrons on the nitrogen more readily available to accept protons.
Why are seondary amines stromnger than primary amines
they have more alkyl groups that are substituted onto the N atom in place of H atoms. Therefore more electron density is pushed onto the N atom (as the inductive effect of alkyl groups is greater than that of H atoms), so making the lone pair of electrons on the nitrogen more readily available.
Why do primary aromatic amines such as phenylamine not form basic solutions
the lone pair of electrons on the nitrogen delocalise with the ring of electrons in the benzene ring. This means the lone pair on the N is less able to accept protons
Overall order of base strength
Aromatic amines < ammonia< primary amines< tertiary amines< secondary amines Secondary amines are strongest bases and aromatic are weakest
amine Reactions with acids
All amines will react with acids to become ammonium salts CH3NH2 (aq) + H+ (aq) –> CH3NH3+ (aq) (CH3CH2)2 NH (aq) + H+(aq) –>(CH3CH2)2NH2 (aq) (CH3CH2)3 N (aq) + H+(aq) –> (CH3CH2)3NH+ (aq)
What happens if you add NaOH to an ammonium salt
will convert it back to the amine
How do you make a basic byffer from an amine
Basic buffers can be made from combining a weak base with a salt of that weak base e.g. Ammonia and ammonium chloride
WHy is an excess of ammonia required in nucleophilic substituion
Using an excess of ammonia can limit the further subsequent reactions and will maximise the amount of primary amine formed
How would you promote the formation of a quarternary salt
Using an excess of the halogenoalkane will promote the formation of the quaternary salt Using a large excess of ammonia will maximise the amount of primary amine formed.
What is the use of quarternary salts And what is thier role
cationic surfactants The positive nitrogen is attracted toward negatively charged surfaces such as glass, hair, fibres and plastics. This helps in their uses as fabric softeners, hair conditioners and sewage flocculants. Surfactants reduce the surface tension of liquids.
How do you get an amine from a halogenoalkane and a nitrile
Step 1. convert halogenoalkane to nitrile by using KCN in aqueous ethanol (heat under reflux) CH3CH2Br + CN- CH3CH2CN + Br - Step 2. reduce nitrile to amine by using LiAlH4 in dry ether or by reducing with H2using a Ni catalystCH3CH2CN + 4[H]–> CH3CH2CH2NH2
What is a disadvantage of reducing nitriles to amines
It is a two step reaction that may therefore have a low yield. Also KCN is toxic.
Reducing nitroarenes to aromatic amines What are the reagents, conditions and mechanism required fro it
Reagent: Sn and HCl or Fe and HCl Conditions: Heating Mechanism: Reduction This reduction reaction can also be done with catalytic hydrogenation (H2 using a Ni catalyst).