Amines

Question 1

How many total isomers does C4H11N have? How many structural isomers?

Answer 1

It has a total of 9 isomers. Only 8 structural isomers becuase one is optically active hence there are d and l forms.

Question 2

Benzene with Nh2 and Ch3

Answer 2

o-Toludine

Question 3

Benzene with NH2 and OCH3

Answer 3

m-Anisidine

Question 4

C6H6CH2NH2

Answer 4

Benzylamine

Question 5

Structure of amines

Answer 5

NItrogen has sp3 hybridised orbitals, 3 sigma bonds, one lone pair, bond angle is 107 in 1 and 2 amines due to lp-bp repulsion but in 3 amines it is 108 due to repulsion between alkyl groups.

Question 6

Preparation of amines by reduction of nitro compounds

Answer 6

Yields primary aliphatic and aromatic amines
General reaction- R-NO2+6H–R-NH2+2H20
REAGENTS USED;
1. Catalytic reduction using H2/Ni, H2/Pd/Pt
2. Using active metals like Fe/Hcl or sn/Hcl
3. Using LiAlH4- gives aliphatic primary amine but azobenzene when treated with nitrobenzene.

Question 7

Why is reduction using iron scrap and HCL preferred

Answer 7

FeCl2 formed gets hydrolysed to produce Hcl thus only a small amount of Hcl is required to initiate the reaction.

Question 8

Hoffman’s ammonolysis

Answer 8

See notes for mechanism.

Question 9

Reduction of cyanides

Answer 9

Gives primary amines
Reagents;
1. H2/ Raney Ni
2. LiAlH4
3. Na/alcohol (Mendiv’s reduction)
4. Na-Hg/alcohol

Question 10

Reduction of isocyanides

Answer 10

Gives N methyl secondary amines

Question 11

Hydrolysis of isocyanides

Answer 11

Gives primary amine+ fomic acid

Question 12

Hydrolysis of nitriles

Answer 12

Gives RCOOH+ NH3

Question 13

Reduction of amides

Answer 13

Requires a strong reducing agent like LiAlH4. Gives primary, secondary or 3 amines depending on the type of amide used.

Question 14

Gabriel phthalimide reaction

Answer 14

Gives primary amine. See mechanism.

Question 15

Hoffman Bromamide Reaction

Answer 15

RCONH2+BR2=4NAOH GIVES RNH2+ NA2CO3+ 2NABR+ 2H2O

Question 16

Methylamine and ethylamine are

Answer 16

Gases

Question 17

Aryl amines are usually

Answer 17

colourless but get colored due to oxidation when stored

Question 18

Boiling point of isomeric amines

Answer 18

1>2>3

Question 19

solubility of amines

Answer 19

As size of alkyl part increases, they become less soluble so that is why higher members are not soluble.

Question 20

Larger the value of Kb or smaller the value of pKb

Answer 20

Stronger is the base.

Question 21

What happens to basicity when there are electron donating groups

Answer 21

Increases

Question 22

What happens to basicity when electron withdrawing groups are present?

Answer 22

decreases

Question 23

Order of basicity in pure state

Answer 23

3>2>1> NH3

Question 24

Which is more basic Ammonia or Alkyl amine

Answer 24

Alkyl amine due to +I effect

Question 25

in aqueous soln, if alkyl group is methyl, then order of basicity is

Answer 25

2>1>3

Question 26

In aqueous soln, if alkyl group is not methyl then order of basicity is

Answer 26

2>3>1

Question 27

Why are Anilines not basic?

Answer 27

Lone pairs are not available since they are involved in resonance. Also anilinium ion formed has only 2 resonating structures, hence it is less stable than Aniline.

Question 28

Acylation of amines

Answer 28

R-NH2+ RCOG GIVES R-NH-CO R. Study mechanism. Remember to use Pyridine in case of aromatic amines.

Question 29

Use of acylation

Answer 29

Since the lone pairs on nitrogen are involved in resonance with CO bond, the basicity gets reduced.

Question 30

What kind of amines do not undergo acylation

Answer 30

tertiary

Question 31

Carbylamine test

Answer 31

Aliphatic and aromatic primary amines react with chloroform in the presence of KOH to give isocyanide, KCl and water. It is a distinguishing test for primary amines.

Question 32

I

Intermediate in carbylamine test

Answer 32

Dichloro carbene

Question 34

Reaction of primary aromatic amines with nitrous acid

Answer 34

Produces Diazonium salt, NaX and water. Takes place in low temperatures like 273-278 K.

Question 35

How does primary aliphatic amines react with Nitrous acid

Answer 35

They produce unstable diazonium salts which liberate nitrogen and alcohol.