4.2.1 Alcohols

Question 1

Explain the solubility of alcohols

Answer 1

The longer the hydrocarbon chain on the alcohol the more insoluble it is. This is due to the hydrocarbon chain being insoluble so reduces interaction water can make with the alcohol

Question 2

Explain why alcohol are polar molecules

Answer 2

O in the OH bond is more electronegative than the H so attracts the electrons in the C-O bond

Question 3

What bonding occurs in alcohols

Answer 3

Hydrogen bonding

Question 4

Describe the oxidation reactions of propan-1-ol when using a suitable oxidising agent.
Indicate how the use of different reaction conditions can control which organic product forms.
Include reagents, observations and equations in your answer.
In your equations, use structural formulae and use [O] to represent the oxidising agent.

Answer 4

Aldehyde -
Reagents : H2SO4 and Kr2Cr207
Condition : Distil Immediately
Equation :CH3CH2CH2OH + (O) > CH3CH2CHO + H2O
Observation : Colour change from orange to green

Carboxylic Acid -
Condition : Reflux
Equation : CH3CH2CH2OH + 2(O) > CH3CH2CHOH + H20

Question 5

Alcohols can be converted into alkenes in an elimination reaction.
The elimination of H2O from pentan-2-ol forms a mixture of organic compounds
Give the names and structures of all the organic products in the mixture
Explain how the reaction leads to different isomers

Answer 5

• The elimination can produce a double bond in either the 1- or the 2- position (through combination of the hydroxyl
  group with a hydrogen from either the 1st or the 3rd carbon)
• Leads to the formation of structural isomers (pent-1-ene and pent-2-ene)
• Pent-2-ene exhibits stereoisomerism / E/Z isomerism
• It has two different groups attached to each carbon atom so there are two possible isomers of pent-2-ene

Names of isomers =
Pent-1-ene
E Pent-2-ene
Z Pent-2-ene

Question 7

Why is butan-2-ol classified as a secondary alcohol?

Answer 7

The OH group is attached to a carbon which is attached to two carbons