Carboxylic acids & esters
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Properties of carboxylic acids
Weak acids Donate H+ ions in reactions Water soluble (if small chains) as they can H bond to water molecules
How much does carboxylic acids dissociate in water? Reaction?
A weak acid so only partially dissociates. RCOOH ⇌ RCOO- + H+
What does a reaction between a carboxylic acid + carbonate form? How can this be tested for?
Sodium salt + water + carbon dioxide Carbon dioxide can be tested for.
2RCOOH + Na2CO3 forms what?
2RCOO-Na+ + water + carbon dioxide
Reaction which occurs in esterification
Carboxylic acids + alcohols -> ester + water
Reagent and condition of esterification
Reagent: Conc H2SO4 Condition: Reflux
Structual formula of products when ethanoic acid (CH3COOH) and ethanol (CH3CH2OH) react together?
CH3COOCH2CH3 + water
Properties of esters
Non toxic Soluble in ethanol Volatile Unreactive with water Can not H bond with other esters (no H bond directly attatched) Low boiling points
Ester uses and why?
Perfume & food flavouring - pleasent smells, non toxic, ethanol soluble, unreactive with water Solvents - Form H bonds with water, cannot bond with esters, low boiling point Plasticisers - Reduce IMF strength and increase flexibility in pure polymers
What are the two opposite reactions to esterification?
Acid hydrolysis Alkali hydrolysis
Reagent and conditions in acid hydrolysis
Reagent: Dilute H2SO4 OR HCl (aq) + water Condition: Reflux
Reaction in acid hydrolysis between ester and water
Ester RCOOR1 + Water H2O -> Carboxylic acid RCOOH + Alcohol R1OH
Reagent and conditions in alkaline hydrolysis
Reagent: NaOH Condition: Reflux
Reaction in alkaline hydrolysis between ester and NaOH
Ester RCOOR1 + Sodium hydroxide NaOH -> Carboxylate salt RCOO-Na+ + Alcohol R1OH
What are fats and oils esters of
Glycerol C3H8O3
What is reacted to form fats and oils
Glycerol + Carboxylic acids
Why do oils have low boiling points?
Unsaturated hydrocarbons chains so cannot pack tightly together. Lower VdW forces and so are liquids.
Why do fats have high boiling points?
Saturated hydrocarbons chains so are compact. Higher VdW forces and so are solids.
What hydrolysis does saponification (soak making) use
Alkaline hydrolysis
Saponification reaction
Fat/Oil + NaOH -> Glycerol + Soap (Sodium salt)
What is biodiesel?
A mixture of methyl esters of long chain carboxylic acids
Catalyst in the formation of biodesial
KOH
Reaction when biodiesel is formed
Vegetable oil + methanol -> glycerol + methyl ester