Amines 3.3.11 Flashcards
how many hydrogens does ammonia have bonded to nitrogen
3
how many hydrogens does a primary amine have bonded to nitrogen
2
1 alkyl group
how many hydrogens does a secondary amine have bonded to nitrogen
1 hydrogen
2 alkyl groups
how many hydrogens does a tertiary amine have bonded to nitrogen
0 hydrogens
3 alkyl groups
what are quaternary ammonium salts used to make
cleaning produces such as shampoo , laundry detergent and washing up liquids
what are quaternary salts made up from and what are they attracted to
made up from a positive end and are attracted to negative ions
what are the long hydrocarbon tails on quaternary salts called
cationic surfactants
how do the cationic surfactants work
The non polar tail is attracted to the oil / grease.
The polar head will be attracted to the water.
This now allows the water and oil to mix and removes grease from clothing , skin and dishes
how are cationic surfactants used in fabric softeners and hair conditioner
Have a positive ammonium ion which is attracted to negatively charged fibres and hair . This removes static
how do amines acts as a base
Have a lone pair of electrons that allow them to accept a proton and hence act as a base
how does a proton bond to an amine
Via a dative covalent bond ( coordinate) . Both electrons in the bond originate from the lone pair on the nitrogen
What is the strength of the base dependent on
the availability of the lone pair of electrons on the nitrogen . The higher the electron density the more readily available the electrons are
what is electron density dependent on
Electron density on the nitrogen is dependent on the type of group attached to the nitrogen
why are aromatic amines the weakest bases
The lone pair on the N is partially delocalised into the benzene ring , leading to a reduction in the electron density on the N atom so weaker base strength
what is the order of base strength from weakest to strongest
Aromatic amines > ammonia > primary amines > secondary amines > tertiary amines
how do alkyl groups make an amine more basic
Alkyl groups are electron pushing groups so they push electrons towards nitrogen . Electron density at nitrogen increases so lone pair availability is increased ( inductive effect )
what are the two ways an aliphatic amine is made
- By reacting a halogenoalkane with excess ammonia ( nucleophilic substitution)
- By reducing a nitrile
what is the downside of using a nucleophilic substitution mechanism with excess ammonia to make aliphatic amines
It produces primary amines as well as secondary , tertiary and quaternary salts too so we have an impure product
if a large excess of ammonia what is the main product
Primary amine
if a large excess of halogenoalkane is used in nucleophilic substitution what is the main product
Quaternary ammonium salt
how can a quaternary salt be produced from primary amine in nucleophilic substitution
The amines produced have a lone pair on the N atom and so further react with halogenoalkanes .
This means that the H on the N can be successfully replaced by ally groups from the halogenoalkanes right through to quaternary ammonium salts
what is the good thing about using reducing nitriles to make amines
This reaction produces a single product so a pure product is made and has higher atom economy
what is the cheapest way to make primary amines in industry
To reduce nitriles using hydrogen gas and a nickel or platinum catalyst
what is the catalyst and conditions used for reducing nitriles with hydrogen gas
Catalyst - Nickel
Conditions - high temp and high pressure
