4.2.1 - Alcohols

Question 1

polarity of alcohols

Answer 1

• polar O-H bond
• difference in electronegativity of O and H atoms
• alcohol molecules are polar
• very weak London forces and strong hydrogen bonds between polar O-H groups

Question 2

water solubility of alcohols

Answer 2

• alcohols are more water-soluble than alkanes
• alkanes are non-polar, can’t form hydrogen bonds with water
• alcohols are completely soluble in water, hydrogen bonds form between polar -OH group and water molecules

Question 3

low volatility (high BPs) of alcohols

Answer 3

• alcohols have higher BPs than alkanes
• strong hydrogen bonds
• need more energy to break

Question 4

primary alcohol

Answer 4

-OH group attached to a C atom that is attached to two H atoms and one alkyl group (methanol exception)

Question 5

secondary alcohol

Answer 5

-OH group attached to a C atom that is attached to one H atom and two alkyl groups

Question 6

tertiary alcohol

Answer 6

-OH group attached to a C atom that is attached to no H atoms and three alkyl groups

Question 7

combustion of alcohols

Answer 7

alcohol + oxygen → carbon dioxide + water

Question 8

oxidation of alcohols

Answer 8

• only primary and secondary
• K₂Cr₂O₇ / H₂SO₄
• colour change: orange → green (tertiary alcohol: stays orange)

Question 9

oxidation of primary alcohols

Answer 9

distillation to form an aldehyde:
alcohol + [O] → aldehyde + H₂O

reflux to form a carboxylic acid:
alcohol + 2[O] → carboxylic acid + H₂O

Question 10

oxidation of secondary alcohols

Answer 10

reflux to form a ketone:
alcohol + [O] → ketone + H₂O

Question 11

dehydration of alcohols

Answer 11

• elimination reaction
• H₂O removed
• uses acid catalyst H₃PO₄ and heat
• forms an alkene

Question 12

substitution reactions of alcohols

Answer 12

• react with sodium halides
• in presence of acid H₂SO₄
• halide ion substituted for -OH group
• forms a haloalkane