27.1 - Amines

Question 1

What are the charactertistics of amino acids?

Answer 1

• Have an amine (-NH₂) and carboxyl directly attached to the same carbon
• Form proteins
• Form peptide bonds
• Can react as acids and bases (due to amine and carboxyl group)
• General formula RCH(NH₂)COOH

Question 2

How do amines behave as bases?

Answer 2

• WEAK BASES
• The lone pair on the nitrogen can accept a proton
• A dative covalent bond forms between the lone pair and the proton forming a positive ion

Question 3

How are amines classified?

Answer 3

Question 4

What happens when amines react with acids?

Answer 4

They neutralise them and form salts.

E.g.

CH₃CH₂CH₂NH₂ + HCl > CH₃CH₂CH₂NH₃⁺Cl^-

2CH₃CH₂NH₂ + H₂SO₄ > (CH₃CH₂NH₃⁺)₂SO₄^2-

Question 5

How are primary amines formed?

Answer 5

• Lone pair on the ammonia acts as a nucleophile
  
  • the product of nucleophilic substitution of a haloalkine is an ammonium salt

1. Salt Formation: (haloalkane + NH₃)
   
   • 1-chloropropane + ammnoia > propylammonium chloride (salt)
2. ​Amine Formation: (ammonium salt + NaOH [strong base])
   
   • _​​_propylammonium chloride + NaOH (strong base) > propyl amine + NaCl + water

Conditions

• :Excess ethanolic ammonia (NH₃/ethanol)

1. Ethanol stops haloalkane being substitued by water to form alcohol
2. Excess ammonia stops further substitution to 2^o or 3^o amine

Question 6

How are secondary or tertiary amines formed?

Answer 6

Haloalkane + 1^o amine > salt

salt + NaOH > 2^o amine

Haloalkane + 2^o amine > salt

salt + NaOH > 3^o amine

Question 7

How are aromatic amines prepared?

Answer 7

Nitrobenzene + 6[H] > (Sn/HCl and excess NaOH) > aniline (aminobenzene)