6.1.3 - Carboxylic acids and Esters Flashcards
Why can carboxylic acids dissolve in polar solvents like water ?
As water can form hydrogen bonds with either the Hydrogen on the -OH group or with the Oxygen on the -CO group.
What happens to the solubility of carboxylic acids as the length of the carbons increase on the alkyl group.
As the carbon chain length of carboxylic acids increases, the larger non-polar alkyl group disrupts hydrogen bonding between the carboxylic acid and water molecules. This reduces the carboxylic acid’s ability to dissolve in water, decreasing solubility
- The only part of the molecule that is polar is the carboxylic group.
What type of acids are carboxylic acids and what does this mean in terms of dissociation ?
- Weak acids
- They will partially dissociate to form H+ ions and a carboxylate ion.
- They are also strong enough to displace carbon dioxide from carbonates
If a carboxylic acid was to react with carbonates what would it form ? Use the example reaction ethanoic acid and sodium carbonate.
Remember they are still acids so will react like acids !
“Describe the reactions of carboxylic acids with metals, alkalis, and carbonates, including the products formed in each reaction.”
Use Sodium for each case in different forms, as the other reactant and ethanoic acid as the carboxylic acid.
Write down the chemical equation between ethanoic acid and sodium hydrogen carbonate including state symbols
If ethanoic acid was to react with magnesium oxide what would be the products ?
As you know alkyl groups are electron donating. With that being said how would increasing chain length affect the strength of the acid ?
Increasing chain length pushes
electron density on to the COO-
ion, making it more negative and
less stable. This make the acid
less strong.
As you know chlorine is electron withdrawing. With that being said how would adding a chlorine group to the carboxylic acid chain length the strength of the acid ?
Electronegative chlorine atoms
withdraw electron density from
the COO- ion, making it less
negative and more stable. This
make the acid more strong.
How can we make esters using carboxylic acids
By reacting them with alcohols in the presences of concentrated sulfuric acid (H2 SO4)
What will the reaction between a carboxylic acid and alcohol produce ?
How do we name esters ?
1st half : -anoate
2nd half : -yl
What will the reaction between a alcohols and acid anhydrides produce ?
What do we use to hydrolyse esters ?
- Dilute acid and heat under reflux
- Base and heat under reflux
What do you know about acid hydrolysis ?
- What are the products
- The condition etc
- It’s split into a carboxylic acid and an alcohol
- We us a dilute HCl or dilute sulfuric acid
- We heat it under reflux
What do you know about base hydrolysis ?
- What are the products
- The condition etc
- We form a carboxylate salt if we use NaOH (O- Na+ or instead a carboxylate ion if we use (OH ions only) and an alcohol
- We use a base (-OH ions) e.g sodium hydroxide
- We heat under reflux
Why are acyl cholrides much more reactive than carboxylic acids ?
- Electron-Withdrawing Effect of the Chlorine Atom: The electronegative chlorine atom withdraws electron density from the carbonyl carbon, making it more electrophilic. This increases the susceptibility of the carbonyl carbon to nucleophilic attack.
- Better Leaving Group: The chloride ion (Cl⁻) is a much better leaving group than the hydroxide ion (OH⁻) found in carboxylic acids. This makes nucleophilic substitution reactions with acyl chlorides faster and more efficient.
As a result, acyl chlorides undergo nucleophilic reactions more readily than carboxylic acids.
What is thee functional group for an acyl chloride ?
-COCl
What is thee functional group for an acyl chloride ?
-COCl
How do we form acyl chlorides ?
By reacting a carboxylic acid with SOCl2 (thionyl chloride)
What happens when you react a acyl chloride with water ?
- Blurt everything you know
- You form a carboxylic acid.
- White fumes (hydrogen chloride gas is given off) so must be done in a fume cupboard,
- This is a nucleophilic addition elimination reaction
What happens when you react ammonia with an acyl chloride.
- Blurt everything you know.
What happens when you react alcohol with an acyl chloride.
- Blurt everything you know.
- You will produce an ester
What happens when you react a primary amide with an acyl chloride.
- Blurt everything you know.
- You will produce a secondary amide (2 R groups, 1 hydrogen)
