carboxylic acids Flashcards
Why are carboxylic acids stronger acids than phenols?
both are resonance stabilised
- carboxylic acids are more acidic because they have 2 oxygen atoms
- carboxylate resonance structures are stronger than phenoxide anion
What is the the effect of electron-withdrawing groups on acidity?
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
What are the properties of carboxylic acids?
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
What is esterification?
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
What are the requirements of esterification? How can you tell which carboxylic acid and alcohol an ester has been formed from?
acid catalyst
ethyl acetate
- ethyl = tells you which alcohol
- acetate = tells you which carboxylic acid
What is the difference in physical properties between carboxylic acids and esters?
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
What is the medicinal use of salicylic acid?
salicylic acid is used in anti-acne cream
What are fats and oils?
fats and oils are triesters of glycerol
What is saponification? What is soap?
saponification
- hydrolysis of lipids and fats under basic conditions to form alcohol and soap
soap
- esters of glycerol = salts of fatty acids
What are the requirements of saponification?
aqueous alkali - basic conditions
water - creates aqueous conditions
How do detergents work?
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