Preparation Of Pure Organic Solid Flashcards
Give general to synthesise and purify an organic product
React suitable quantities of reactants to produce product
Filter under pressure using Büchner flask to separate product from reaction mixture
Recrystallise to remove impurities
Dry product in low temperature oven
Use melting point test to test purity
Apparatus for reduced pressure filtration
Horizontal filter paper
Büchner flask
Büchner funnel
Side arm to vacuum
Method for recrystallisation
Dissolve sample in minimum volume of hot solvent
Filter hot to prevent recrystallisation while filtering
Cool filtrate in a beaker place in ice bath
Filter cold and wash thoroughly with cold water
Why dissolve in minimum amount of hot solvent
Creates saturated solution to Maximise yield
Why filter hot
Prevent recrystallisation while filtering and to remove insoluble impurities
Why cool filtrate in ice bath during filtration
Increase amount of crystals formed
Why wash final product of recrystallisation with cold water
To remove any soluble impurities
How is a solvent chosen for recrystallisation
Product is soluble at high temperature and insoluble at low temperature
How can you dry a product
Low temperature oven
Placing between 2 filter papers
Placing in a dessicator with drying agent
Method for melting point test
Use melting point apparatus provided to heat sample
Heat slowly close to melting point
Record temperature at which product starts to melt and when it finishes melting
Pure samples will melt over 1-2 degrees and have a melting point close to data book value
How do the melting points of impure products compare
Lower melting point than expected and have a larger range
Why is ethanoic anhydride better than ethanoyl chloride
Cheaper
Less corrosive
Less vulnerable to hydrolysis
Less dangerous
Alcohol + acid anhydride —->?
Ester + carboxylic acid
Method to produce aspirin
Place 20g of salicylic acid in pear shaped flask and add 40cm3 of ethanoic acid
Add 5cm3 H3PO4 and heat under reflux for 30 mins
Add anti bumping granules
Add water to hydrolyse unreacted acid anhydride and pour into crushed ice
Filter under pressure, recrystallise, wash and dry
Test melting point
