carboxylic acids

Question 1

Why are carboxylic acids stronger acids than phenols?

Answer 1

both are resonance stabilised

• carboxylic acids are more acidic because they have 2 oxygen atoms
• carboxylate resonance structures are stronger than phenoxide anion

Question 2

What is the the effect of electron-withdrawing groups on acidity?

Answer 2

electron withdrawing groups = electronegative groups

• increase acidity
• electronegative atoms pull electron density with the sigma bonds
• weakens the O-H bond inductively

lower the pka the more acidic

Question 3

What are the properties of carboxylic acids?

Answer 3

highly polar
low molecular weight carboxylic acids are soluble in water
- can be tested by adding drops of water and using blue litmus paper which would turn red
high boiling point
- form extensive hydrogen bonds to themselves and water

Question 4

What is esterification?

Answer 4

formation of esters from carboxylic acids and alcohols
- is a condensation reaction = removal of water (formed as a product)

carboxylic acid + alcohol = ester + water
- replaces the H atom on the OH group of the carboxylic acid with the R group of the alcohol

Question 5

What are the requirements of esterification? How can you tell which carboxylic acid and alcohol an ester has been formed from?

Answer 5

acid catalyst

ethyl acetate

• ethyl = tells you which alcohol
• acetate = tells you which carboxylic acid

Question 6

What is the difference in physical properties between carboxylic acids and esters?

Answer 6

carboxylic acids have higher boiling points than esters
- carboxylic acids can form hydrogen bonds but esters cannot
carboxylic acids are more soluble in water than esters
- esters of low molecular weight are soluble in water = solubility decreases with chain length

Question 7

What is the medicinal use of salicylic acid?

Answer 7

salicylic acid is used in anti-acne cream

Question 8

What are fats and oils?

Answer 8

fats and oils are triesters of glycerol

Question 9

What is saponification? What is soap?

Answer 9

saponification
- hydrolysis of lipids and fats under basic conditions to form alcohol and soap

soap
- esters of glycerol = salts of fatty acids

Question 10

What are the requirements of saponification?

Answer 10

aqueous alkali - basic conditions

water - creates aqueous conditions

Question 11

How do detergents work?

Answer 11

have a hydrocarbon chain = non-polar
sulfonate = polar

form micelles

• hydrophobic tail face inward and hydrophilic head face outwards
• grease/dirt is suspended inside = is solubilised
• removes dirt/grease by drawing it away