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Module 6 - Chapter 26 - Carboxylic acids - Coggle Diagram
Module 6 - Chapter 26 - Carboxylic acids
Solubility
C=O and O-H are polar allowing carboxylic acids to form hydrogen bonds with water molecules
Carboxylic acids with up to four carbons are soluble in water
Increasing number of carbons decreases solubility as non-polar chain has greater effect on overall polarity
Di carboxylic acids have two polar carbonyl groups to form hydrogen bonds
Acid reactions
Carboxylic acids form carboxylate salts during redox reactions with metals and neutralisation with bases
Redox
Aqueous carboxylic acids react with metal to form hydrogen gas and carboxylate salt
Metal disappears and effervescence is observed
Neutralisation
React with metal oxides to form salt and water
React with alkalis to form salt and water
React with carbonates to form salt, CO2 and water
Derivatives
Compound that can be hydrolysed to from the parent carboxylic acid
They all have acyl group
Esters
Name - remove oic acid from carboxylic acid and replace with oate. Alkyl chain attached to oxygen atom of COO group is added as the first word
Acyl Chlorides
Name - Remove oic acid from suffix and replace with -oyl chloride
Acid anhydrides
Remove of water from two carboxylic acids
Name - '-oic, -oic- anydride. If two carboyxlic acids are the same, just say once, eg ethanoic anhydride
Esterification
Alcohol reacts with carboxylic acids to from an ester
Alcohol is watrmed with carboxylic acids with small amount of concentrated sulfuric acid (catalyst)
Making an ester
Pour alcohol and carboxylic aicds into boiling tube
Add few drops of conc. sulfuric acids and place in beaker of hot water for 5 minutes
Pour contents of boiling tube into beaker with aquous sodium cabrbonate to neutralise unreacted carboxylic acid
Hyrolysis of ester
Hydrolysis - chemical breakdown of a compound in presence of water/ in aqeous solution
Acid hydroylsis
Reverse of esterifcation
Ester is heated under refluc with dilute sulfuric acid (catalyst)
Ester is broken down by water to form carboxylic acid + alcohol
Reversible reaction
Alkaline hydrolysis
Ester is heated under reflux with aqueous hydroxide ions
Carboxylate ion and alcohol are formed (irreversible)
If sodium hydroxide is alkali, a salt is formed
Reaction goes to copmletion, and more product produced than acidic condition as COOH and OH produed in acid hydrolysis and reform ester again
Acyl chlorides
Forming
SO2 and HCl are produced, they're toxic gases so reaction should be carried in a fum cupboard
React carboxylic acid with thionyl chloride (SOCl2)
Acyl chlorides are very reactive
Esterification
Alcohols
HCl is produced too
Acyl chlorides react with alcohols to form esters
Phenols
Carboxylic acids aren't reactive enough to form esters with phenols
Acyl chlorides and acid anhydrides are more reactive and react with phenols to produce phenyl esters without a catalyst
Reaction with water
When water is added, vioent reaction takes place and dense hydrogen chloride fumes are produced
Carboxylic acids is formed
Forming amides
Ammonia and amines can act as nucleophiles by donating lone pair of electrons on nitrogen
Primary
Ammonia reacts with acyl chloride
Nitrogen atom is attatched to one carbon atom
HCl produced reacts with ammonia to form a salt (acid + base)
Secondary
Primary amine reacts with acyl chloride
Nitrogen atom is attatched to two carbon atoms
It's names N- (alkyl group) to show us it's attached to the nitrogen rather than a carbon atom of the main carbon chain
Reactions of acid anhydrides
Acid anhydrides are less reactive than acyl chlorides
useful for some laboratory preparations when acyl chlorides may be too reactive
React with alcohols to form esters and carboxylic acids
Mechanism
Reaction between acyl chlorides and nucleophiles
Addtion
Lone pair of electrons from nucleophile is attracted and donated to dipole positive carbon atom in C=O group in acyl chloride
Dative colvaent bond is formed between nucleophile and carbonyl carboin atom
Pi bond of C=O break, negatively charged intermediate forms
Elimination
Lone pair of electrons on oxygen reforms the C=O double bond, causing chloride ion to be removed
Proton is lost to complete elimindation
