Carboxylic acids and esters Flashcards
What is the general formula of a carboxylic acid?
COOH
How do you name carboxylic acids?
-oic acid.
Are carboxylic acids soluble in water? Why?
Yes - the acid group forms hydrogen bonds with water molecules.
What are the intermolecular forces in carboxylic acids?
Hydrogen bonds.
What are esters formed from?
Carboxylic acids and alcohols.
What is the functional group of on ester?
COO-
What is the general formula of an ester?
RCOOR’
Write an equation for the reaction of ethanoic acid with propan-1-ol.
CH3COOH + CH3CH2CH2OH → CH3COOCH2CH2CH3 + H2O
How do you name esters?
Start is from alcohol, end is from carboxylic acid.
What physical properties do esters have?
*volatile
*pleasant fruity smell
What are some uses of esters?
*flavourings
*perfumes
*solvents
*plasticisers
What are some common natural esters?
Fats and oils.
Draw a diagram showing the way a carboxylic acid is polarised.
…
Write an equation for the equilibrium formed by ethanoic acid in solution.
CH3COOH (aq) ⇌ CH3COO- (aq) + H+ (aq)
What happens to the negative charge on the ethanoate ion in terms of electrons?
Electrons delocalise so the negative charge is shared across the whole of the carboxylate group.
How would you distinguish between carboxylic acids and other compounds containing -OH?
Add NaHCO3 - acids will produce sodium, salt, water and carbon dioxide.
Write an equation for the reaction of ethanoic acid with NaOH.
CH3COOH + NaOH → H2O + CH3COO-Na+
Write an equation for the reaction of ethanoic acid with Na2CO3.
2CH3COOH + Na2CO3 → 2CH3COO-Na+ + CO2
What catalyst is needed for the formation of esters from alcohols and carboxylic acids?
Concentrated strong acid (e.g. H2SO4).
What catalyst is needed for the hydrolysis of esters?
Dilute strong acid.
What is an alternative method of hydrolysis?
Base hydrolysis.
What are the advantages of base hydrolysis?
Reaction goes to completion due to neutralisation by the base - more product in the mixture than acid-catalysed hydrolysis.
Which alcohol forms the esters that make up animal and vegetable oils?
Glycerol/propane-1,2,3-triol
What is the difference between oil and fat?
*at room temp, oils are liquid, fats are solid
*fats are saturated, oils are not
What are the products of hydrolysing fats and oils?
Propane-1,2,3-triol and sodium salts of the acids that make up the ester.
What are the uses of the products of hydrolysis of fats and oils?
Soaps and cleaning products.
What does the long hydrocarbon chain of the carboxylate ion do?
Mixes with grease.
What does the COO- group do?
Mixes with water.
How does the carboxylate ion with a long carbon chain make a good cleaning agent?
Means that grease can be removed from water.
What is the systematic name of glycerol?
Propane-1,2,3-triol.
What are some common uses of glycerol?
*pharmaceutical and cosmetic preparations
*solvent in medicines (toothpaste)
*solvent in food industry (food colouring)
*plasticising various material (sheets, gaskets, cellophane, paper)
What is the equation for making biodiesel?
lipids + 3CH3OH → 3 methylesters + glycerol
What are the conditions for making biodiesel?
*NaOH catalyst
*60°C
What is transesterification?
Converting one type of ester to another.
What kind of crops is biodiesel made from?
*rapeseed oil
*soybean oil
How is the reaction mixture of biodiesel purified and separated?
*settling tank/centrifuge
*remove remainder with water
*add acid to neutralise excess alkali catalyst
*solid soap is formed (easy to remove)
What is a problem with producing biodiesel?
Is is using crops that could be used for food.
What are carboxylic acid derivatives?
Molecules that have the acyl group as part of their structure, formed from carboxylic acids.
