Carboxylic Acids And Derivitives Flashcards
How do you name carboxylic acid with two carboxylic group
If there are carboxylic acid groups on both ends of the chain then it is called a - dioic acid
Can carboxylic acids dissolve in water
‘The smaller carboxylic (up to C4) acids dissolve in water in all proportions but after this the solubility rapidly reduces. They dissolve because they can hydrogen bond to water
Why is propanoic acid less acidic than ethanoic acid
Increasing chain length pushes electron density on to the COO- ion,
making it more negative and less stable.
This make the acid less strong.
Why is chloroethanoic more acidic than ethanoic acid
Electronegative chlorine atoms withdraw- electron density from the COO ion,
making it less negative and more stable.
This make the acid more strong
How can methanol acid undergo oxidation
Unlike other carboxylic acids ,methanoic acid contains an an aldehyde group
How are esters formed
When carboxylic acid reacts with an alcohol in the presence of a strong catalyst
How are esters named
The first part ending with -yl comes from the alcohol that has formed
The -late come from the carboxyl group
E.g ethyl ethanoate
What are the uses of esters
For perfumes
Used as solvents
Used as plasticisers
Describe the hydrolysis of esters
They can be hydrolysed and split by either heating with an acid or with sodium hydroxide
Using
Reagents:dilute HCL
Conditions:heat under reflux
Describe hydrolysis of esters using sodium hydroxide
Using excess sodium hydroxide ensures the ester is completely hydrolysed
Reagent:dilute sodium hydroxide
Conditions:heat under reflux
Why is the reaction irreversible when using a sodium hydroxide reagent in hydrolysis of esters
The carboxylic acid salt produced is an anion
The anion is resistant to attack by weak nucleophiles
So reaction is not reversible
What are fats and oil comprised of
Glycerol and long chain carboxylic acids
What is the formula for glycerol
Propan-1,2,3-triol
Is glycerol soluble
Forms hydrogen bonds easily
So very soluble
What is formed when vegetable oil is hydrolysed
Soap
Glycerol
Long chain carboxylic acid
Why can water and soap mix
-Long chain of carboxylic fatty acids are produced by the hydrolysis of fats
- the polar CO2- end is hydrophilic and mixes with water
-the long non-polar hydrocarbon chain is hydrophobic
-allows grease and water to mix
What is used to hydrolyse vegetable oils
-KOH
What is biodiesel
A mixture of methyl esters of long chain of carboxylic acids
How can vegetable oil be converted into biodiesel
Reaction with methanol and vegetable oil in the presence of catalyst
2CH3OH
Why are acyl chlorides more reactive than carboxylic acids
The -Cl and -OCOCH3 are good leaving groups
How is aspirin formed
When 2-hydroxybenzoic acid reacts ethanoic anhydride
Forming an ester
CH3COH
why is inportnat to dissolve the impure compound in a minimum volume of hot solvent
Minimum volume:
To obtain a saturated solution and to enable crystallisation
Hot solvent :
To dissolve compound and the impurities
Why is the filtration of solution through filter paper
Removes any insoluble impurities
Will prevent crystals reforming during filtration
Why is filtered solution cooled in ice
So crystals will reform
soluble impurities remain in solution
Ice will increase the yield of crystals
Why is it important to wash the crystals with distilled water
To remove soluble impurities
How is there loss of yield during process
-crystals lost when filtering
-some products stays in solution after recrystallisation
How is the degree of purity tested
By determining the melting point
What happens to the melting point if impurities are present
The melting point is lowered
The sample will melt over a range of several degrees
