3.3.9 Carboxylic acids and derivatives Flashcards
3.3.9.1 Carboxylic acids and esters
Outline the structure of a carboxylic acid.
RCOOH
end with -oic acid
3.3.9.1 Carboxylic acids and esters
Outline an example of the structure of a carboxylic acid.
CH3CH2COOH
Propanoic acid
3.3.9.1 Carboxylic acids and esters
Outline an example where there a carboxylic acids at each end.
HOOCCOOH
ethanedioic acid.
3.3.9.1 Carboxylic acids and esters
Describe the physical properties of a carboxylic acid.
- can form H bonds with H2O molecules.
- COOH up to 4C are soluble in H2O.
- form H bonds with each other in solid state.
- higher mp than alkanes.
3.3.9.1 Carboxylic acids and esters
Describe the acidity of carboxylic acids.
Weak acids } will partially dissociate in H2O.
They will react with carbonates to form CO2.
3.3.9.1 Carboxylic acids and esters
State why delocalisation occurs.
The carboxylic acids salts are stablised by delocalisation, making the dissociation more likely.
3.3.9.1 Carboxylic acids and esters
Describe how a delocalised ion forms.
H3C-C=O-OH →delocalised →H3C-C-O-O
- H on OH group is lost } carboxylate ion is formed.
- Delocalised ion has equal C-O bond lengths.
- Delocalisation makes ion more stable and more likely to form as the pi charge cloud is delocalised and has spread out.
3.3.9.1 Carboxylic acids and esters
What would happen if delocalisation did not occur?
The C=O would be shorter than the C-O bond.
3.3.9.1 Carboxylic acids and esters
What group is electron releasing?
Alkyl group.
3.3.9.1 Carboxylic acids and esters
How are alkyl groups electron releasing?
H3C-CH2-COOH → delocalised →H3C-CH2-COO
- Increase in chain length pushes e- denisty onto COO- ion.
- more negative
- less stable } acid less strong.
3.3.9.1 Carboxylic acids and esters
What functional group is electron withdrawing?
Chlorine.
3.3.9.1 Carboxylic acids and esters
How is Cl electron withdrawing?
H2ClC-COOH→deloc.→H2ClC-COO
- EN- Cl atom withdraws electron density from COO- ion.
- Less negative
- More stable } acid is more strong.
3.3.9.1 Carboxylic acids and esters
What is the inductive effect?
The pushing away or withdrawal of electrons.
3.3.9.1 Carboxylic acids and esters
How can salts be formed using carboxylic acids?
COOH can form salts with metals, alkalis and carbonates.
3.3.9.1 Carboxylic acids and esters
Acid + metal →
CH3COOH + Na →
salt + hydrogen
CH3COO-Na+ + H2
3.3.9.1 Carboxylic acids and esters
Acid + Alkali (base)→
CH3COOH + NaOH →
Salt + water
CH3COO-Na+ + H2O
3.3.9.1 Carboxylic acids and esters
Acid + carbonate →
2CH3COOH + CaCo3 →
Salt + water + Co₂
(CH3COO-)₂Ca+ + H₂O + CO₂
3.3.9.1 Carboxylic acids and esters
How are esters formed?
COOH + alcohol ⇌ ester + H2O
in the prescence of an acid catalyst.
3.3.9.1 Carboxylic acids and esters
Outline a generic example of the formation of esters.
R-COOH + R-OH ⇌ R-COO-R + H2O
3.3.9.1 Carboxylic acids and esters
What is the general formula of esters?
RCOOR’
3.3.9.1 Carboxylic acids and esters
How to name esters?
1st part: alcohol
2nd part: COOH
3rd part: remove “-oic acid” and add “-oate”
H3C-CH2-COO-CH2-CH3
ethyl propanoate
think of the OO in COO as zero so you must start counting from there for both the carboxylic part and alcohol part.
3.3.9.1 Carboxylic acids and esters
What are the common uses of esters?
- Perfumes and food flavouring } sweet-smelling, non-toxic and soluble in solvent.
- Plasticiers } used for polymers, limited flexibility (pure polymer), adding plasticiers to polymer allows it to move easily, more flexible.
- Solvents } polar, low bp (evapourate easily), insoluble in H2O.
3.3.9.1 Carboxylic acids and esters
In what conditions can esters be hydrolysed in?
Acid
Alkaline
