Amines

Question 1

Define Amines

Answer 1

Nitrogen containing organic compounds from ammonia where an H is replaced by alkyl or aryl (benzene) group

Question 2

What are the three types of amines?

Answer 2

Primary
Secondary
Tertiary

Question 3

What can tertiary amines be further substituted to?

Answer 3

Quaternary ammonium salts

Question 4

What is the shape of amines?

Answer 4

Pyramidal

Question 5

What is the shape of Quaternary ammonium salt?

Answer 5

Tetrahedral

Question 6

Amine properties: why do amines act as bases?

Answer 6

Bc of their lone pair- accepts proton

Question 7

Which amines are stronger bases an why?

Answer 7

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+

Question 8

What is the inductive effect?

Answer 8

the R group ‘releases’ electrons towards N
More R groups means greater inductive effect
Greater ability for N to pull in H+

Question 9

Which of secondary and tertiary amines are better bases and why?

Answer 9

Secondary
Tertiary amines ability to act as bases decreases as they become less soluble in water
-counteracts greater inductive effect

still better than primary

Question 10

Order of basic: amines etc.

Answer 10

Secondary
Tertiary
Primary
Ammonia
Aromatic Amines

Question 11

Why are aromatic amines not good bases?

Answer 11

The lone pair on the N overlaps with the delocalised ring structure
Electrons are pulled away from the N

Question 12

Preparation for amines to act as nucleophiles
2 stages?
Reagents?

Answer 12

Alkylation
-haloalkane + ammonia –> alkylammonium salt

Proton exchange
-Alkylammonium salt + ammonia —-> primary amine + ammonium salt

Question 13

Draw out the mechanism for the formation of primary amines
2 steps?
Products?

Answer 13

Alkylation
-Alkylammonium salt

Proton exchange
-Primary amine + NH4X

Question 14

What are the formation of amine mechanism?

Type- eg: electrophilic sub

Answer 14

Nucleophilic substitution

Question 15

Draw out the mechanism for the formation of secondary amines
2 steps?
Products?

Answer 15

Second Alkylation
-dialkyl ammonium salt

Proton exchange
-secondary amine + ammonium salt

Question 16

Draw out the mechanism for the formation of tertiary amines
2 steps?
Products?

Answer 16

Third Alkylation
-trialkyl ammonium salt

Proton exchange
-tertiary amine + ammonium salt

Question 17

Draw out mechanism for formation of quaternary ammonium salt
Products?
Step?

Answer 17

Fourth alkylation

-quaternary ammonium salt

Question 18

What is another (superior) method for producing primary amines?
Reagents?
1st Step?
Conditions?
Two options for 2nd step?

Answer 18

1. RX + KCN ——> RC-N + KX
   - ethanolic, RCN = intermediate and triple bond
2. a: RC-N —LiAlH4—> RCNH2
   - LiAlH4
3. b: RC-N —H2—> RCNH2
   - Nickel catalyst

Question 19

What is important about the KCN method for producing primary amines?

Answer 19

It increases carbon chain length

Question 20

Draw out method for forming phenylamines
2 steps?
Conditions?
Products?

Answer 20

1. benzene ——> benzene w/ NO3
   - conc H2SO4 and HNO3
2. benzene w/ NO3 + 6[H] —> RCNH2
   - H2 and nickel catalyst

Question 21

Why do you need to add excess of NaOH when making phenylamines?

Answer 21

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

Question 22

Soaps- structure and function?

Answer 22

Long alkyl tail

• hydrophobic
• dissolves grease

Ionic head

• hydrophilic
• dissolves in water

overall:
dissolves grease and can be washed away with water

Question 23

difference between detergents and soaps

Answer 23

detergents contain aromatic systems

Question 24

Detergents and soaps how they work?

Answer 24

Form micelles

take oil/grease into micelles so it can be washed away with water

Question 25

quaternary ammonium salts in conditioner?

Answer 25

positively charged
attracted to neg charged strands of hair/fabric - when wet
-fabric/hair conditioner