6.2.3: Amines and Amides Flashcards
Amine
When one or more hydrogens in ammonia (NH3) are replaced with an organic group such as an alkyl or aromatic group
Primary amine
and general formula
one hydrogen in ammonia is replaced with an organic group
NH2R
Secondary amine
and general formula
two hydrogens in ammonia are replaced with organic groups
NHR2
Tertiary amine
and general formula
all (three) hydrogens in ammonia are replaced with organic groups
NR3
Quaternary ammonium ion
and general formula
all (three) hydrogens in ammonia are replaced with organic groups and a fourth organic group is added
NR4+
Quaternary ammonium ions form
Quaternary ammonium salts
with nearby negative ions
Naming amines
suffix: -amine or -amine ion
prefix: di, tri, tetra for secondary, tertiary and quaternary amines
Cationic surfactants
Positively charged compounds which are partly soluble and insoluble in water
Quaternary ammonium salts as cationic surfactants
quaternary ammonium salts with at least one long hydrocarbon chain which is insoluble in water but will bind to non-polar substances such as grease whilst the polar head group will dissolve in water and therefore mix with grease and wash away
Cationic surfactants
uses
fabric conditioners and hair products
How do amines act as bases
Act as weak bases by accepting protons. A lone pair of electrons on the nitrogen atom form a co-ordinate/dative bond with an H+ ion
What does the strength of a base depend on
The availability of a lone pair of electrons as more likely to accept a proton.
A lone pair is more available if electron density is higher
Order of base strength between,
primary aromatic amines, primary aliphatic amines and ammonia
primary aromatic amines: weak bases
ammonia: in between strength
primary aliphatic amines: strong bases
Aliphatic meaning
contains an alkyl group
Why are primary aromatic amines the weakest base
the benzene ring draws the electrons towards itself which makes the lone pair of electrons less available
