Amines Flashcards
Define Amines
Nitrogen containing organic compounds from ammonia where an H is replaced by alkyl or aryl (benzene) group
What are the three types of amines?
Primary
Secondary
Tertiary
What can tertiary amines be further substituted to?
Quaternary ammonium salts
What is the shape of amines?
Pyramidal
What is the shape of Quaternary ammonium salt?
Tetrahedral
Amine properties: why do amines act as bases?
Bc of their lone pair- accepts proton
Which amines are stronger bases an why?
All aliphatic (alkyl groups) amines better bases than NH3 IE: secondary and tertiary over primary
Due to positive inductive effect
- more R groups means greater inductive effect
- Greater ability for N to pull in H+
What is the inductive effect?
the R group ‘releases’ electrons towards N
More R groups means greater inductive effect
Greater ability for N to pull in H+
Which of secondary and tertiary amines are better bases and why?
Secondary
Tertiary amines ability to act as bases decreases as they become less soluble in water
-counteracts greater inductive effect
still better than primary
Order of basic: amines etc.
Secondary Tertiary Primary Ammonia Aromatic Amines
Why are aromatic amines not good bases?
The lone pair on the N overlaps with the delocalised ring structure
Electrons are pulled away from the N
Preparation for amines to act as nucleophiles
2 stages?
Reagents?
Alkylation
-haloalkane + ammonia –> alkylammonium salt
Proton exchange
-Alkylammonium salt + ammonia —-> primary amine + ammonium salt
Draw out the mechanism for the formation of primary amines
2 steps?
Products?
Alkylation
-Alkylammonium salt
Proton exchange
-Primary amine + NH4X
What are the formation of amine mechanism?
Type- eg: electrophilic sub
Nucleophilic substitution
Draw out the mechanism for the formation of secondary amines
2 steps?
Products?
Second Alkylation
-dialkyl ammonium salt
Proton exchange
-secondary amine + ammonium salt
Draw out the mechanism for the formation of tertiary amines
2 steps?
Products?
Third Alkylation
-trialkyl ammonium salt
Proton exchange
-tertiary amine + ammonium salt
Draw out mechanism for formation of quaternary ammonium salt
Products?
Step?
Fourth alkylation
-quaternary ammonium salt
What is another (superior) method for producing primary amines? Reagents? 1st Step? Conditions? Two options for 2nd step?
- RX + KCN ——> RC-N + KX
- ethanolic, RCN = intermediate and triple bond - a: RC-N —LiAlH4—> RCNH2
- LiAlH4 - b: RC-N —H2—> RCNH2
- Nickel catalyst
What is important about the KCN method for producing primary amines?
It increases carbon chain length
Draw out method for forming phenylamines
2 steps?
Conditions?
Products?
- benzene ——> benzene w/ NO3
- conc H2SO4 and HNO3 - benzene w/ NO3 + 6[H] —> RCNH2
- H2 and nickel catalyst
Why do you need to add excess of NaOH when making phenylamines?
The phenylamine is still basic so has the ability to react w/ HCl to start forming phenylammonium salt
-liberate free amine
NaOH reacts w/ phenylammonium salt back to phenylamine
Soaps- structure and function?
Long alkyl tail
- hydrophobic
- dissolves grease
Ionic head
- hydrophilic
- dissolves in water
overall:
dissolves grease and can be washed away with water
difference between detergents and soaps
detergents contain aromatic systems
Detergents and soaps how they work?
Form micelles
take oil/grease into micelles so it can be washed away with water
quaternary ammonium salts in conditioner?
positively charged
attracted to neg charged strands of hair/fabric - when wet
-fabric/hair conditioner
