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Flashcards in Amines Deck (22):
1

What are amines?

If one or more hydrogens in ammonia (NH3) is replaced with an organic group, you get an amine.

2

Why are amines considered bases?

Amines will accept protons. There's a lone pair of electrons on the nitrogen atom that forms a dative (coordinate) bond with an H+ ion.

3

Amines + acids = ?

Amines are neutralised by acids to make an ammonium salt.

4

How are aliphatic amines made?

By heating a haloalkane with an excess of ethanolic ammonia.You get a mixture of primary, secondary and tertiary amines and quaternary ammonium salts.Of which you can fractionally distil.

5

How are aromatic amines made?

By reducing a nitro compound.Nitro compounds are reduced in two steps:1. Heat a mixture of nitro compound, tin metal and conc HCl under reflux- making a salt.2. Add sodium hydroxide.

6

What are aromatic amines used to make?

Azo dyes

7

What are azo dyes?

Man made dyes that contain the azo group, -N=N-.The azo group links two aromatic groups- creating a very stable molecule (the azo group becomes part of the delocalised electron system).

8

What are the colours of azo dyes a result of?

Light absorption by the delocalised electron system.Different colours are made by combining different phenols and amines.

9

Give some uses of azo dyes.

Food colouringsColours for clothingPaint pigmentsIndicators (methyl orange)

10

State why some conditions must be kept at a low temperature.

Prevent decomposition

11

Process of making an azo dye

1. Nitration- to get NO2 on 2. Reduction with tin and HCl (to swap NO2 for NH2)3. React the phenyl amine with nitrous acid and HCl

12

Boiling point trend in amines

• Boiling points increase with molecular mass. • Amines have higher boiling points than corresponding alkanes because of intermolecular hydrogen bonding.

13

Solubility of amines

• Soluble in organic solvents. • Lower mass compounds are soluble in water due to hydrogen bonding with the solvent. • Solubility decreases as molecules get heavier.

14

Why are amines bases?

The lone pair on nitrogen makes amines basic. RNH2 + H+—> RNH3+

15

Strength of bases in amines

• depends on the availability of the lone pair and thus its ability to pick up protons• the greater the electron density on the N, the better its ability to pick up protons• this is affected by the groups attached to the nitrogen.

16

When 1-chloropropane is reacted with ethanolic ammonia what two amines may have been produced?How would this mixture be seperated?

Propylamine, dipropyl amineFractional distillation

17

What are the equations for the usage of H2SO4 in nitration?

H2SO4 + HNO3 -> H2NO3+ + HSO4-H2NO3+ -> NO2+ + H2O (how NO2+ is produced).HSO4- + H+ -> H2SO4 (how its a catalyst that's reformed).

18

Equation for the production of an ammonium salt?

CH3CH2NH2 + HCl -> CH3CH2NH3+Cl-

19

1. Making phenylamine conditions (nitrogenation)

50 degrees Conc H2SO4

20

2. Reduction conditions

HCl Tin catalyst

21

3. Diazotisation

React phenylamine with nitrous acid and HCl Less than 10 degrees

22

4. Coupling

Couple the diazonium salt with a phenol that has been dissolved in NaOH solution (phenol is a coupling agent- it increases the electron density in the benzene ring.) Then chill in ice- azo dye precipitates out.