Amines Flashcards
What is an aryl group?
a benzene ring
Difference between primary/secondary/tertiary amines?
number of H attached to the N
How do you name simple amines?
if more than one place the amine group could go - add number-amino(chemical)
ethylamine
2-aminopropane
phenylamine
How do you name secondary amines?
N- (what H was replaced with) amino - rest of molecule
N-methylaminoethane
How do you name tertiary amines?
N,N- dimethylaminomethane
What can amines behave as?
bases/nucleophiles/ligands
When amines act as bases…
the lone pair is donated to a proton
When amines act as nucleophiles…
the lone pair is donated to an electron deficient carbon
When amines act as ligands…
the lone pair is donated to a transition metal ion
How are dative bonds shown when the amine acts as a bronsted-lowry base?
–> solid arrow from N to H+
What do amines react with acids to make? eg- CH3NH2 + HCl
soluble salts - CH3N+H3Cl- (methylammonium chloride)
Amines in water make…
an alkaline solution
What does the strength of amines as a base depend on?
the availability of the lone pair on the nitrogen for protonation (stronger bases, more availability)
What is the relationship between alkyl groups and the availability of the lone pair?
alkyl groups push the electrons onto the attached group, meaning they are electron releasing, which increases the availability of the lone pair. longer alkyl chain length = more available
Order these in terms of strongest to weakest base:
methylamine
ammonia
ethylamine
phenylamine
ethylamine
methylamine 1<2<3, as more alkyl groups
ammonia
phenylamine
Why are aromatic amines weaker bases than ammonia?
the lone pair gets involved in delocalisation stabilisation, drawing away from the attached group
How to find pKa?
-log (Ka)
How to compare relative base strengths of amines?
stronger bases have higher pKa values
Which mechanisms have amines reacting as nucleophiles?
-nucleophilic substitution
-nucleophilic addition-elimination
What can happen after NH3 and a haloalkane react?
the primary amine formed have a lone pair of electrons on the N that can also react with another haloalkane, forming a secondary amine. the secondary amine can then go on to react with another to form a tertiary amine. it can then happen AGAIN to form a quaternary ammonium salt
Why can a quaternary ammonium salt not act as a nucleophile?
no lone pair
How do you reduce the chance of further substitution?
large excess of ammonia used, would give a better yield of the primary amine
How is a high yield of a quaternary ammonium salt achieved?
large excess of haloalkane
What is a use for quaternary ammonium salts?
cationic surfactants in fabric conditioners/hair products- -reduce the static due to negatively charged electrons
What are amines used for?
to make polymers like polyamides (nylon fibres for clothes/carpets) and drugs like painkillers and polyurethanes (cavity wall insulation)
How can you make primary aliphatic amines?
-2 step synthesis:
-make a nitrile through a nucleophilic substitution (+:CN-)
-reduction to a primary amine by catalytic hydrogenation (2H2/Ni/150C)
ie- butanenitrile –> 1-aminobutane
Why can’t we use catalytic hydrogenation when there is a ketone group?
would reduce it to a 2ndary alcohol
Why will metal/acid combinations NOT reduce a ketone?
they are weaker reducing agents
