Amines

Question 1

Amine

Answer 1

Nitrogen containing organic compund

Question 2

Primary Amine

Answer 2

has only one C atom directly bonded to the nitrogen atom and therefore has -NH2 group

R-NH2

Question 3

Secondary Amine

Answer 3

two carbon atoms directly bonded to the nitrogen atom

R2NH

Question 4

Tertiary Amine

Answer 4

has three carbon atoms directly bonded to the nitrogen atom

R3N

Question 5

Amine with benzene

Answer 5

Phenylamine

Question 6

Amine mp and bp

Answer 6

N-H polar so H bonds between
Higher mp and bp than similar RMM alkanes

N-H less polar than O-H so lower mp and bp than similar RMM alcohols

Question 7

Amine Solubility

Answer 7

Short chain soluble in water

Less soluble than alcohol

Question 8

Prep of Aliphatic Amine from Reduction of Nitrile

Answer 8

Nitrile Refluxed with LiAlH4 in dry ether

Question 9

Prep of Aliphatic Amine from Reaction of Halogenoalkanes w/ NH3

Answer 9

HA mixed with ammonia in ethanolic solution - heated in a sealed tube in absence of air

Tube opened in NaOH sol - converts alkylammonium ion to amine

Question 10

Prep of Phenylamine From Nitrobenzene

Answer 10

Reducing agent: tin and conc HCl

Reflux nitrobenzene with tin and conc HCl followed by addition conc NaOH sol for liberation of free amine - phenylammonium chloride formed (NaOH converts this back to phenylamine)

Question 11

Amines As Bases

Answer 11

All amines act as bases - accept H+ from acid

Do this bc of lone pair on N atom can form coord bond with H+

Positive ion formed = alkylammonium ion or phenylammonium ion

Question 12

Order of Basic Strength

Answer 12

1. 3°
2. 2°
3. 1°
4. Ammonia
5. Phenylamine

Question 13

Basicity of Amines Explain

Answer 13

Depends on ability to accept H+

Benzene ring delocalises lone pair so stabilises lp - weaker base

Alkyl groups push e- towards N - destabilises - stronger base Alkyl

Question 14

Amine with Ethanoyl Chloride

Answer 14

Question 15

Preparation Nitrous Acid

Answer 15

HNO2 prepared in situ in reaction vessel from sodium nitrite and HCl

Question 16

Phenylamine with Nitrous Acid

Answer 16

Below 5° forms Benzene Diazonium Ion (C6H5N2+)

Only stable below 5°

Due to presence of HCl - salt is usually Benzene Diazonium Chloride

Question 17

Benzene Diazonium Ion

Answer 17

Question 18

Benzene Diazonium reaction Above 5°

Answer 18

Unstable when warmed - reacts with water in aqueous solution to form Phenol

Colourless Gas produced - N2

Question 19

Coupling Reaction

Answer 19

one in which two benzene rings are linked through an azo group (-N=N-)

Question 20

Benzene Diazonium Chloride w/ Phenol

Answer 20

No gas evolved, azo formed - coupling reaction

Azo is yellow ppt

Question 21

Benzene Diazonium Chloride w/ Phenylamine

Answer 21

No gas, coupling, yellow azo formed (aniline yellow)

Question 22

Why are dyes coloured

Answer 22

They have an extended pi-delocalised system that brings energy levels closer together - light is absorbed in visible region of the spectrum

Question 23

Azo Dye Colours

Answer 23

Absorbance around 400nm at violet end of spectrum gives azo dye cream or yellow colour

Large extended pi-deloc sys brings energy levels even closer - naphthalen-2-ol absorbs more blue light - orange-red solid (Sudan I dye)

Question 24

How colours work

Answer 24

Colour observed is often called complementary colour of colour absorbed

Question 25

Aliphatic Amines With Nitrous Acid

Answer 25

Diazonium ion formed from aliphatic is not stable at any temp - breaks down immediately to alcohol Amine mixed with sodium nitrite and HCl- Colourless gas prod (N2) immediately (even below 5°)