Amines

Question 1

What are amines?

Answer 1

Organic compounds, derived from ammonia (NH3), in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring.

Question 2

What are the 2 types of amines?

Answer 2

1. Aliphatic amines.
2. Aromatic amines.

Question 3

What are aliphatic amines?

Answer 3

The nitrogen atom is attached to at least one straight or branched carbon chain (alkyl group, R).

Question 4

What is the simplest aliphatic amine?

Answer 4

Methylamine, CH3NH2 = one methyl group attached to the nitrogen atom.

Question 5

What are aromatic amines?

Answer 5

Where the nitrogen atom is attached to an aromatic ring (aryl group, Ar).

Question 6

What is the simplest aromatic amine?

Answer 6

Phenylamine, C6H5NH2, with a phenyl C6H5 group attached to the nitrogen atom.

Question 7

What should you always add when drawing an amine?

Answer 7

The lone pair on the nitrogen.

Question 8

What are the 3 classifications of amines?

Answer 8

Primary, secondary, or tertiary.

Question 9

What is the difference between primary, secondary, and tertiary amines?

Answer 9

• Primary amines have 1 alkyl/aryl group attached to the nitrogen atom.
• Secondary amines have 2 alkyl/aryl groups attached to the nitrogen atom.
• Tertiary amines have 3 alkyl/aryl groups attached to the nitrogen atom.

Question 10

What is the displayed structure of an amine?

Answer 10

H - N - H
l
H

Question 11

How do you name primary amines (when on carbon 1)? Example?

Answer 11

Add the suffix -amine onto the prefix of the alkyl group. For example, ethylamine.

Question 12

How do you name a primary amine when the amine group is not attached on carbon 1? Example?

Answer 12

Use the prefix -amino and add a number to indicate the position. For example, 2-aminobutane.

Question 13

How do you name secondary and tertiary amines with the same alkyl groups? Example?

Answer 13

Use the prefixes -di or -tri to indicate the number of alkyl groups attached to the nitrogen atom. For example, dimethylamine.

Question 14

How do you name secondary and tertiary amines with 2 or more different alkyl groups attached to the nitrogen atom? Example?

Answer 14

The compound is named as an N-substituted derivative of the larger group and if multiple this is done in alphabetical order. For example, N-ethyl-N-methylpropylamine.

Question 15

How do amines act as bases?

Answer 15

They behave as bases in their chemical reactions as the lone pair of electrons on the nitrogen atom can accept a proton.

Question 16

What happens when an amine group accepts a proton when they act as bases?

Answer 16

A dative covalent bond is formed between the lone pair of electrons on the nitrogen atom and the proton.

Question 17

What is the equation for reactions of amines as a base?

Answer 17

Amine + H+ = Ammonium ion.

Question 18

What is an example reaction of amines acting as a base?

Answer 18

Ethylamine + H+ = Ethylammonium ion.

Question 19

As amines are bases, what can they do?

Answer 19

Neutralise acids to form salts.

Question 20

What is the reaction for amines to form salts?

Answer 20

Amine + Acid = Salt.

Question 21

What are 2 examples reaction of amines forming salts?

Answer 21

1. Propylamine + HCl = Propylammonium salt (CH3CH2CH2NH3+Cl-).
2. Ethylamine + H2SO4 = Ethylammonium salt (CH3CH2NH3+)2SO42-.

Question 22

What is the equation for forming primary amines? (2)?

Answer 22

Salt Formation:
Ammonia + Haloalkane = Ammonium salt.

Amine formation:
Ammonium salt + NaOH (aqueous alkali) = Primary amine + Salt + H2O.

Question 23

How does ammonia act as a nucleophile?

Answer 23

Because it has a lone pair of electrons on the nitrogen atom, so acts as a nucleophile in nucleophillic substitution.

Question 24

What is an example reaction for forming primary amines? (2)?

Answer 24

Salt Formation:
1-chloropropane + NH3 = Propylammonium chloride (salt).

Amine Formation:
Propylammonium chloride (salt) + NaOH = Propylamine + NaCl + H2O.

Question 25

What are the 2 conditions for the reaction of forming primary amines using haloalkanes?

Answer 25

1. Ethanol is used as a solvent. This prevents any substitution of the haloalkane by water to produce alcohols.
2. Excess ammonia is used. This reduces further substitution of the amine group to form secondary or tertiary amines.

Question 26

What is the equation to form a secondary amine? (2)?

Answer 26

Salt Formation:
Primary amine + Haloalkane = Diammonium salt.

Secondary Amine Formation:
Diammonium salt + NaOH = Secondary amine + Salt + H2O.

Question 27

What is an example reaction for forming secondary amines? (2)?

Answer 27

Salt Formation:
Propylamine + 1-chloropropane = Dipropylammonium chloride (salt).

Amine Formation:
Dipropylammonium chloride (salt) + NaOH = Dipropylamine + NaCl + H2O.

Question 28

How are tertiary amines formed?

Answer 28

By the further reaction of secondary amines. In this reaction, tripropylamine.

Question 29

What is the equation to form a tertiary amine? (2)?

Answer 29

Salt Formation:
Secondary amine + Haloalkane = Triammonium salt.

Secondary Amine Formation:
Triammonium salt + NaOH = Tertiary amine + Salt + H2O.

Question 30

How do you prepare aromatic amines? Reduction? Equation? (2)?

Answer 30

Nitrobenzene + 6[H] = Ammonium salt + 2H2O.

• On the (=), you have Tin/conc. HCl heated under reflux and Excess NaOH (aq).

1. Nitrobenzene is heated under reflux with tin and HCl to form the ammonium salt (phenylammonium chloride).
2. React this with excess NaOH to produce phenylamine.

• Tin and HCl act as a reducing agent.