Carbonyl compounds: Carboxylic acids and esters Flashcards
What is the functional group of carboxylic acid?
-COOH (carboxyl functional group)
Does the carboxylic acid take priority when compounds are named?
Yes, as they go at the end so they take priority when compounds involving carboxylic acids are named
Are carboxylic weak or strong acids? And what is the equilibrium position when it reacts with water
They are weak acids and so only partially dissociate into H+ ions, so the equilibrium lies well to the left
Carboxylic acid + water
Carboxylate ion (RCO2-) + water
carboxylic acids + carbonates CO3(2-
e.g. CH 3 COOH + Na 2 CO 3
carbon dioxide + water + salt (e.g.)
CH 3 COOH + Na 2 CO 3 → 2 CH 3 COONa + CO 2 + H 2 O
what functional group do esters belong to?
-COO
How are esters most often formed?
Carboxylic acid + alcohol in the presence of a strong acid catalyst such as concentrated sulfuric acid in a process known as esterification
How do you name an ester?
- First stems from the alcohol e.g. propyl
- Second bit is from the ethanoic acid, where the oic acid is replaced with oate e.g. ethanoate
- Add the 2 together e.g. propyl ethanoate
If the chain is branched then, number from the C carbon in C-O-C bond, e.g. propyl 2-methyl ethanoate
What type of liquid are esters and hence what dissolves in them?
They are polar liquids and polar organic compounds dissolve in them
Why are esters useful as glues and paints?
They have low boiling points and so evaporate from mixes easily
How are esters used as plasticisers and what happens to them over time?
They are added to plastics during polymerisation to make them more flexible, the plasticisers can escape over time and then it becomes brittle and stiff
What forms as esters are hydrolysed by water?
They form alcohol
Why are acids or bases added when esters and water react?
To sped up the process
What occurs and forms in the acid hydrolysis of the ester: ethyl ethanoate?
- Reflux the ester with a dilute acid, e.g. sulfuric or hydrochloric acid to reach equilibrium
- forming an ethanol (alcohol) and ethanoic acid (acid)
What occurs and forms in the base hydrolysis of the ester: ethyl ethanoate?
- Reflux the ester with an alkali such as sodium hydroxide to reach equilibrium
- Ethanol (alcohol) and ethanoate (carboxylate ion) are both formed
what are fatty acids?
They are long chains of carboxylic acids, which can be saturated or unsaturated
glycerol + fatty acids
Form esters which are fats and oils
Why are animal fats solid at room temperature?
They are mostly saturated, so pack tightly with stronger van der waals between them, so they require higher temperatures to melt and are therefore solid at room temperature
Why are plant oils liquid at room temperature?
They are unsaturated which means the double bonds cause them to bend, so they don’t pack tightly, hence weaker van der waals and are easier to melt
what is the by product of ester, animal fat and vegetable oil hydrolysis when its heated with sodium hydroxide?
They form glycerol, soap and fatty acids
How is biodiesel formed?
veg oils, e.g. rapeseed oil is heated in the presence of a potassium hydroxide catalyst , you get a mixture of methyl esters of fatty acids- biodiesel
CH 3 COOH + NaH CO 3
CH 3 COOH + Na H CO 3 –> CO2 + H2O + CH3COONa
