Amines Flashcards
Classes of amines
Number of alkyl groups connected to N atom
N-methylethanamine
CH3CH2NHCH3
Chemical test for an amine
Conc. HCl gives white fumes
Why propan-1-amine can act as a base
It has a lone pair on the N so can accept a proton to form a dative covalent bond
Equation showing propan-1-amine acting as a base
CH3CH2CH2NH2 + H2O CH3CH2CH2N+H3 + OH-
Why butan-1-amine is a stronger base than ethanamine
Longer carbon chain
Greater electron releasing effect from alkyl group
Lone pair more available to accept a proton
Why is phenylamine a weaker base than ammonia
The lone pair is partially delocalised into the benzene ring
Lone pair is less able to accept a proton
Ammonia + bromopropane equation
CH3CH2CH2Br + 2 NH3 > CH3CH2CH2NH2 + NH4Br
Roles of ammonia in reaction with bromopropane
First acts as a nucleophile attacking 𝛿+ C to replace Br
Then acts as a base accepting a proton from bromopropane
Reaction between ethanamine and bromopropane
Type
Nucleophilic substitution
Reaction between ethanamine and bromopropane, Mechanism
ethanamine N lone pair > 𝛿+ C
C-Br > Br
N+-H > N+
(:Br-)
Reaction between ammonia and bromopropane
Type
Nucleophilic substitution
Reaction between ammonia and bromopropane
Mechanism
NH3 lone pair > 𝛿+ C
C-Br > Br
NH3 lone pair > H
N+-H > N+
(+ :Br-)
(+ NH4Br)
Why does NH3 + bromopropane have a low yield
Further substitution occurs as product contains a lone pair so can act as a nucleophile
Unless an excess of NH3 is used
Use of quaternary ammonium salt and why
Fabric softener - coat fibres with positive charges allowing them to move past each other more easily
