Alcohols

Question 1

How does classification of alcohols work?

Answer 1

Primary - The OH group is on a carbon with one alkyl group
Secondary - The OH group is on a carbon with two alkyl groups
Tertiary - The OH group is on a carbon with three alkyl groups

Question 2

Combustion of alcohols (equation and details)

Answer 2

• Alcohols burn in excess oxygen to product CO₂ and H₂O
• Burn readily with a light blue flame

CH₃OH(l) + 1.5O₂ –> CO₂ + H₂O

Question 3

Chlorination of alcohols (producing chloroalkanes)

Answer 3

Alcohols can be chlorinated by HCl or PCl₅

Using PCl₅:
ROH + PCl₅ –> RCl + HCl + POCl₃

Using HCl:
ROH + HCl –> RCl + H₂O
(Tertiary alcohols react the fastest with HCl)

Question 4

Bromination of alcohols (producing bromoalkanes)

Answer 4

• An inital reaction needs to take place for HBr to be produced

Initial reaction: KBr + H₂SO₄ –> HBr + KHSO₄
(A 50% conc sulfuric acid is used)

Bromination reaction: HBr + ROH –> RBr + H₂O

Question 5

Iodination of alcohols (producing iodoalkanes)

Answer 5

• Phosphorus triodide (PI₃) is used, produced in situ
  How PI₃ is made: 2P + 3I₂ –> 2PI₃

Iodination reaction: SP + 3I₂ –> 2PI₃

Question 6

Dehydration of alcohols/forming alkenes by elimination (eliminating water)

Answer 6

• Uses an acid catalyst (either H₂SO₄ or phosphoric acid, H₃PO₄)

Alcohol –> alkene + H₂O

ex. C₂H₅OH –> C₂H₄ + H₂O

Question 7

How many different alkenes are produced by the dehydration of non-primary alcohols?

Answer 7

Non primary alcohols can produce 3 different alkenes

The double bond (made when the alkene forms) can form either side of the carbon that had the OH group

E/Z isomerism forms two different versions of the same positioned alkene