Carboxylic acids Flashcards
What is the functional group of carboxylic acids?
-COOH.
What type of acids are carboxylic acids?
Weak, meaning the extent of their ionisation on aqueous solution is very small.
What is the order of acidity of alcohols, carboxylic acids and phenols?
Carboxylic acids > phenols > alcohol/water.
What reaction shows the acidity of carboxylic acids?
Reacting them with sodium hydrogencarbonate produces bubbles of CO2 gas.
How are carboxylic acids reduced?
Using the reducing agent LiAlH4 with ethoxyethane to make a primary alcohol.
What are the two methods to marking an aromatic carboxylic acid?
Oxidise a primary alcohol or aldehyde using acidified potassium dichromate.
Oxidise a methyl side chain by heating the compound with alkaline potassium manganate solution.
What are the side products of making an aromatic carboxylic acid?
Other than benzenecarboxylic acid, manganese oxide and benzaldehyde are also made.
What is decarboxylation?
The removal of CO2 from a compound.
What is one use for decarboxylation?
Shortening the carbon chain, as the hydrocarbon produced from this reaction contains one less carbon than the starting material.
What does CO2 react with in decarboxylation?
Soda lime, which is a mixture of calcium hydroxide with a little sodium/potassium hydroxide.
How can carboxylic acids be converted to esters?
Heating the carboxylic acid and an alcohol with a little H2SO4.
Why is H2SO4 added in esterification?
To initially protonate the carboxylic acid.
Which compound loses its -OH group in esterification?
The carboxylic acid, along with a H from the alcohol to make water.
How can you hydrolyse an ester?
Heat to reflux with aqueous NaOH, then add dilute HCl to acidify and produce the carboxylic acid.
What factors affect the rate of hydrolysis of esters?
The particular ester
The concentration of alkali used
What is an industrial use for the hydrolysis of esters?
Soap making.
How do you make an acid chloride from a carboxylic acid?
Either:
Add PCl3
Add PCl5
Add SOCl2
Which reagent is preferred in the synthesis of acid chlorides?
SOCl2 as the side products are SO2 and HCl which are gases so the acid chloride can be extracted easily.
Why are acid chlorides very reactive?
The carbonyl carbon atom is electron deficient (δ+) as it is bonded to the more electronegative Cl and O atoms. As a result, acid chlorides are susceptible to attack by nucleophiles.
How can acid chlorides be converted back to carboxylic acids?
Smaller molecule acid chlorides react very vigorously with water, forming a carboxylic acid and HCl.
How do the reactivities of different acid chlorides compare?
Benzoyl chloride reacts with water much more slowly and its reactions can be carried out in aqueous conditions, whereas ethanoyl chloride needs a fume cupboard and andhydrous conditions.
How are carboxylic acids converted to amides?
Heating the acid with urea at 120°C, producing your amide, CO2 and NH3.
How can amides be dehydrated?
Heating with phosphorus (V) oxide (P4O10), giving a nitrile.
How can nitriles be formed from halogenoalkanes?
Adding KCN and using an alcohol-water mixture as a solvent, to get a nucleophillic substitution reaction.
How do aldehydes and ketones react with HCN?
They will react to produce a hydroxynitrile.
How can a nitrile be hydrolysed?
They can be heated under reflux with dilute H2SO4, giving a carboxylic acid.
What is the functional group of nitriles?
-C≡N
What is the functional group of amines?
-NH2
How can you produce ammonia gas from an amine?
Heat under reflux with NaOH to get a carboxylic acid salt and ammonia gas.
How can you reduce a nitrile to a primary amine?
Warming with a solution of LiAlH4 in ethoxyethane
Hydrogen and a nickel catalyst
Sodium metal
Which reagent is preferred in the reduction of nitriles?
LiAlH4, as the other reagents produce a secondary amine as a byproduct.
How can aromatic nitriles and primary amines be separated?
Adding HCl, which the amine will react with, giving a water soluble salt
Extract the products with water, as some primary amines are soluble in water.
