Topic 28: Amines Flashcards
Amine functional group
R-NH2
Naming amines
Methylamine CH3NH2
Ethylmethylamine (C2H5)(CH3)NH
Making an amine using haloalkane
Nucleophilic substitution of haloalkane with :NH3 creates primary amine
Only make primary amine
Excess ammonia otherwise the amine can act as the nucleophile with the haloalkane to make a secondary alkane.
Quaternary amine use
Cationic surfactant, used in hair conditioner
Making an amine from nitrile
Reduction of nitriles
Reducing agent [H]
CH3CH2CN + 4[H] —> CH3CH2CH2NH2
Reducing agent for making amine from nitrile
LiAlH4 in ether
or
2H2 with Ni catalyst
Amines as bases
Increases in “goodness” of base as lone pair becomes more available.
Most available in primary amine then ammonia then phenylamine
Inductive effect
Electron pushing effect
Making phenylamine
Nitrobenzene is reduced to phenylamine
Conditions for making phenylamine
Tin catalyst, conc. HCl, under reflux makes H2, hydrogen then reduces nitrobenzene by removing the O2
Intermediate of making phenylamine
Phenylammonium salt then reacts with NaOH this makes phenylamine and water
Boiling point of amines
Increases with Mr Higher than alkanes as H bonding
Quaternary amines
Ammonium salts (+ve charge)
Ionic
Aromatic amines
NH2 on benzene ring - phenylamine
Solubility of amines
Decreases as get heavier,
Lower mass soluble in water as H bonding
Soluble in organic solvents
Amines acids/bases
Bases, lewis as lone pair (on N) donor and Bronsted Lowry as proton acceptors
Amines as nucleophiles
Lone pair on N can attack e- deficient centre
Strength of amines as bases
Increased electron density on N means able to pick up protons eaiser
Electron withdrawing substituents on amines
Benzene rings, decrease e- density on N so lone pair is less effective, so decreased basicity
Electron releasing substituents on amines
CH3 groups, electron density is increased on N so lone pair more effective, so increased basicity
Amines and water
CH3NH2(g) + H2O(l) <===> CH3NH3+(aq) + OH-(aq)
weak alkaline solution
Amines in acids
C6H5NH2(l) + HCl(aq) —> C6H5NH3+Cl- (aq)
Produce salts (phenylammonium chloride)
Ammonium salts with sodium hydroxide
C6H5NH3+Cl-(aq) + NaOH(aq) —> C6H5NH2(l) + NaCl(aq) + H2O(l)
N substituted amines
Prefix letter N, to show that the other group is attached to the nitrogen
Conditions for prep of amines with haloalkanes
Reflux in aqueous, alcoholic solution under pressure
Conditions for prep of amines with nitriles
Reflux in aqueous, ethanolic solution
https://www.youtube.com/watch?v=KW8IPSYTq08
