Carboxylic acids Flashcards
Carboxylic acids
Homologous series of hydrocarbon with the functional group COOH
Carboxylic acid solubility in water
Contain an oxygen bonded to hydrogen thus can form hydrogen bonds to water and water can form hydrogen bonds to it so is soluble
Solubility in water trend
Decreases as the carbon chain length increases because the carbon chain cannot form H bonds to water thus does not dissolve
Solubility in organic solvents
Increases as carbon chain length increases
Dissociation in water of carboxylic acids
To form a carboxylate ion: COO-
and H+ ion
Dioic acids
Molecules that have 2 COOH groups at both ends of a carbon chain
Dimers
When short chain carboxylic acids bonds with just one other carboxylic acid: 2 H bonds between each other
Boiling points of carboxylic acids
Form H bonds between each other due to having O bonded to H
Therefore a lot of energy is required to overcome these H bonds and break
They have these as well as permanent dipole-dipole interactions
3 methods of making carboxylic acids
Oxidise primary alcohols
Oxidise aldehydes
Hydrolysis of nitriles
Oxidising agent to form carboxylic acid
Acidified potassium dichromate ions
H+/Cr2O7 2- ions
Conditions for oxidation of aldehyde/primary alcohol to carboxylic acid
Reflux
With oxidising agent acidified potassium dichromate
Hydrolysis of nitriles
Breaking the C=N bond and replacing with OH and O to form a carboxylic acid
Aka using water to break CN bond
By refluxing a nitrile in dilute HCl or KOH
2 conditions for hydrolysis of nitriles
Acid (H+ ions and 2H2O)
Or alkali (OH- ions and H2O)
Hydrolysis of nitrile under acidic conditions
Nitrile + H+ ions + 2H2O forms a carboxylic acid and ammonium ion
Hydrolysis of nitrile under alkaline conditions
Nitrile + H2O + OH- forms a carboxylate ion and ammonia
