3.2 Synthesis d - Haloalkanes

Question 1

What are haloalkanes?

Answer 1

substituted alkenes in which one or more of the hydrogen atoms is replaced with a halogen atom

Question 2

Explain the structure of monohaloalkanes

Answer 2

• they only have one halogen atom
• ## primary, secondary or tertiary

Question 3

Explain the elimination reactions of monohaloalkanes

Answer 3

• take part in elimination reactions to form alkenes using a strong base, such as potassium or sodium hydroxide in ethanol

Question 4

What are the 3 nucleophilic substitution reactions of monohaloalkanes?

Answer 4

Forming:
- alcohols
- ethers
- nitriles

Question 5

Explain the formation of alcohols from nucleophilic substitutions

Answer 5

• nucleophilic substitution reactions
  monohaloalkane + aqueous alkalis = alcohols

Question 6

Explain the formation of ethers from monohaloalkanes

Answer 6

• nucleophilic substitution reactions
  alcoholic alkoxide + monohaloalkane = ether

Question 7

Explain the formation of nitriles from monohaloalkanes

Answer 7

• nucleophilic substitution reactions
  monohaloalkanes + ethanolic cyanide = nitrile

Question 8

What can then happen to nitriles?

Answer 8

undergo hydrolysis to form carboxylic acids by acid hydrolysis or alkaline hydrolysis

Question 9

Haloalkanes and steric hinderance and the inductive stabilisation of the carbon intermediate

Answer 9

• more methyl groups and less hydrogen means a more stable carbon intermediate - the more likely it will be an Sn1 mechanism
• more methyl groups and the less hydrogen means there will be more steric hinderance so an Sn2 mechanism is less likely