Carboxylic Acids
No description yet. This curated deck is ready for daily study.
Card preview (24)
What is the functional group of a carboxylic acid?
-COOH
How are carboxylic acids formed?
Oxidising primary alcohols under reflux
Which carboxylic acids are more soluble? Why?
Those with a lower Mr The -COOH forms hydrogen bonds with water
Why are carboxylic acids only weak acids?
They only slightly dissociate in water
How is a carboxylate ion formed?
The carbonyl group attracts e- away from the -OH group which leads to the -OH bond being weakened so a proton is easily lost
Why are alcohols not acidic?
The -OH bond does not easily break
How does adding a halogen to a carboxylic acid affect the pH? Eg chloroethanoic acid
Chlorine atom is more electronegative so withdraws e- density away from the carbonyl carbon. This causes the O-H bond to become more polar and weaken. More H+ is therefore released, decreasing the pH
What is more acidic: ethanoic acid or chloroethanoic acid Why?
chloroethanoic acid Cl pulls e- towards itself
How are acyl chlorides formed?
The -OH group of the carboxylic acid is replaced by a chlorine atom
Why is the carbon atom in acyl chlorides readily attacked by nucleophiles?
Cl and O are more electronegative than C so the C atom is delta positive
How are acyl chlorides named?
It is derived from their corresponding carboxylic acid Eg ethanoic acid forms ethanoyl Chloride
When there is an -OH in the middle of a carbon chain, how can you refer to it in the name?
With ‘hydroxy’
How to form acid anhydrides from carboxylic acids?
-OH group is replaced by -OCOR When two molecules of carboxylic acids join with the elimination of water
How do you name an acid anhydride?
The suffix -anhydride replaces the -acid suffix at the end of the carboxylic acid name If the two C chains are different, write them in alphabetical order
What is a good leaving group?
A stable species removed during a chemical reaction
What is the leaving group of acyl chlorides? What is the by product?
Cl- HCl
What is the leaving group of an acid anhydride? What is the by product?
-OCOR The corresponding carboxylic acid
Name the mechanism and reaction name for acylation
Nucleophilic addition elimination Reduction
Describe nucleophilic addition elimination
Nucleophile attacks the delta positive carbon of the carbonyl group forcing the e- to move from the carbonyl bond to the O making an oxyanion Carbonyl bond remade causing elimination of the leaving group Nucleophile loses a H+
How are carboxylic acids formed? (3)
1) primary alcohols or aldehydes oxidised by acidified potassium dichromate 2) acyl chlorides react with water (nucleophilic addition elimination) 3) acid anhydrides react with water
Test for carboxylic acids What is formed?
Add Sodium carbonate and CO2 is evolved and fizzing is seen Ionic salts - these are soluble in water
Name of reaction to form an Ester What are the reactants? What is the byproduct?
Esterification Carboxylic acid + alcohol with concentrated H2SO4 (or another strong acid) as a catalyst Water
What is the isomerism linking esters and carboxylic acids?
They are functional group isomers
How do you name an Ester?
The alkyl chain of the alcohol is the prefix The second part of the name is derived from the carboxylic acid - -oic is replaced with -oate