Amines Flashcards
What is a primary, secondary and tertiary amine? Draw them
Primary 1° - one carbon directly bonded to the nitrogen atom
Secondary 2° - two carbons directly bonded to the nitrogen atom
Tertiary 3° - three carbons directly bonded to the nitrogen atom
Why are amines soluble in water?
The polar N-H, the N is slightly
-ve and the H is slightly +ve. They form H-bonds with the water molecules, therefore are soluble
Reduction of nitriles
-C (triple bond)N what can reduce nitriles to primary (1°) amines. Give the conditions
Tetrahydridoaluminate (lll)
Lithal
LiAlH4
Conditions- refluxes in dry ether
Show a reduction of ethanenitrile stating an appropriate reducing agent
1st page of amines notes.
CH3C(triple bond)N + 4[H] —> CH3CH2NH2
Reaction of halogenoalkanes and ammonia.
Describe the conditions and reagents and give an example e.g. bromoethane and ammonia
Mixed in ethanolic solution, heated in a sealed tube in the absence of air. Opened in sodium hydroxide solution which converts alkylammonium ion to the amine
CH3CH2Br + NH3 —> CH3CH2NH2 + HBr
1st page of amines notes
Preparation of phenylamine from nitrobenzene.
What are the reducing agents?
Write the eqn for the reaction between nitrobenzene and the reducing agent.
What are the conditions?
Write the eqn where sodium hydroxide liberated the phenylamine
Reducing agent - Tin and concentrated HCl
C6H5NO2 +6[H] —> C6H5NH2 + 2H20
Reflux nitrobenzene with tin and concentrated HCl with the addition of sodium hydroxide solution to liberate the amine.
C6H5NH3+Cl- + NaOH —> C6H5NH2 + NaCl + H20
Why can amines act as bases?
Give an example of methylamine and hydrochloric acid
They can accept a proton (H+) from an acid therefore acting as a base. The N has a line pair of electrons that forms a coordinate bond with the H+ ion.
CH3NH2 + HCl —>CH3NH3+Cl-
Are amines alkaline or acidic in solution?? Why?
Alkaline due to their reaction with water,
CH3NH2 + H2O —> CH3NH3 + OH-
The OH- is the alkaline bit
What does basic strength depend on?
Your ability to accept a H+ ion
What does a benzene ring do to the LP on the N atom
It delocalises the Lone Pair on the N atom into the delocalised system which stabilises it
What does an alkyl group do to the lone pair on the Nitrogen atom
It pushed the electrons towards the N atom which destabilises the lone pair
Put ammonia, 3° amine, phenylamine, 2° amine and 1° amine in order of decreasing basic strength
Tertiary amine Secondary amine Primary amine Ammonia Phenylamine
Reactions of amines with ethanoyl chloride
e.g. ethylamine and ethanoyl chloride
CH3CH2NH2 + CH3COCl —> CH3CONHCH2CH3 + HCl
Reaction with nitrous acid
What is the formula or nitrous acid?
How is nitrous acid prepared?
HNO2
Prepared in situ from sodium nitrite and hydrochloric acid
Reactions with nitrous acid
What are the conditions for phenylamine to react with nitrous acid and what is formed ?
Below 5°C and forms the benzene diazonium ion C6H5N2+
Reactions of the benzene diazonium ion.
Above 5°C what does it form when warmed?
Give the reaction of benzene diazonium chloride.
What’s is observed?
Reacts with H20 to form phenol
C6H5N2Cl + H2O —> C6H5OH + N2 + HCl
Colourless gas N2
Give the formula of an Azo group
—N (double bond) N—
Give the coupling reactions of the benzene diazonium ion with both phenol and phenylamine.
State the colour of both the precipitates.
Give the name of both products
Look on last page of amines notes
Why are dyes coloured?
What happens when there’s a bigger Pi delocalised system
Dyes are coloured because they have an extended Pi delocalised system that brings the electronic energy levels closer together and so light is absorbed in the visible region of the spectrum.
The larger the Pi delocalised system the more light that will be absorbed
Aliphatic amines with nitrous acid
What happens to the diazonium ion and give a reaction e.g. ethyl amine
What is it mixed with?
It is not stable at any temperature and breaks down to form the alcohol
CH3CH2NH2 + HNO2 —> CH3CH2OH + N2 + H2O
Mixed with sodium nitrite and hydrochloric acid
What are the conditions for benzene diazonium chloride to react with phenol?
Warmed
