RP10- Pure Organic Compounds Flashcards
How would you measure the melting point of aspirin?
- use melting point apparatus
- heat between 100-200C
- slowly near the expected melting point
What are the 3 main steps in forming an organic solid?
- synthesis
- filtration
- recrystallisation
Why is reflux used?
- prevent sample from boiling dry
- allows heating for long periods of time
- ensures even heating
- prevents compounds/substances from escaping
How would the melting point of crude aspirin differ from that of pure aspirin?
- greater range of temperatures
- lower
Why do you add the minimum volume of hot solvent?
ensure solution is saturated
Why do you cool to recrystallise?
yield is lower if warm
Why do you filter after adding hot solvent?
remove insoluble impurities
Why is a buchner funnel used?
allows better drying, air passes through and not just around
Why do you wash with cold solvent at the end?
remove soluble impurities
Describe recrystallisation…
- dissolve in minimum volume of hot solvent
- filter to remove insoluble impurities
- cool to recrystallise
- filter using buchner funnel
- wash with cold solvent then dry
Why is reflux used?
- heating for long time
- prevents flask from boiling dry
- ensures even heating
How do you isolate an organic liquid?
use a separating funnel to isolate liquid layer from organic layer
How do you purify an organic liquid product?
- add anhydrous MgSO4 to remove water
- purify using distillation
Outline how you would test if a solvent was suitable for use in this practical…
- add small amounts of sample and cold solvent, shake, if dissolves UNSUITABLE
- add paracetamol and solvent, heat, if does not dissolve = UNSUITABLE, if dissolves partially, add more
- when dissolved, place in ice bath, crystals = SUITABLE
- test using melting point
How is an ester formed?
react alcohol and acid under reflux with H2SO4 catalyst
