synthesis Flashcards
fingerprint region
below 1500
rough area of C-H peak
3000
molecular ion peak
highest peak, on right hand side of mass spectrum = molecular mass of compound/substance
amount of bond bend/strectch depends on: (2)
- mass of atoms (heavier = vibrate more)
- strength of bonds (stronger = vibrate more/faster)
SHC eq.
q (heat energy given out) = mcΔT
enthalpy change (per mole) eq.
= -q / number of moles reacting
what do you need for heating under reflux? (5)
- pear shaped flask
- condenser
- rubber tubing
- stand and clamp
- heat source
what do you need for distillation? (9)
- pear shaped flask
- condenser
- rubber tubing
- heat source
- stand and clamp
- screw cap adaptor
- receiver adapter
- still heat
- thermometer
how do you separate an organic product (liquid)
- pour mix into funnel
- place stopper on and invert
- add water to see which layer increases in volume = aq layer
- place conical flask under and open tap, until lower layer is gone
- add Na2CO3, add stopper and invert, open tap and allow gas to escape - removes acid impurities
how do you purify a (separated) organic product (liquid) – [drying]
- agent typically used
- add drying agent using spatula (CaSO4) and swirl
- place stopper to prevent evaporation and leave for 10
- if solid is stuck together there is still liquid - add more drying agent and repeat
- continue adding until solid is dispersed like a fine powder
- decant liquid into another flask
how do you separate a solid from liquid mixture?
- connect pressure tubing to vacuum outlet and attach other end to Buchner flask
- fit funnel to flask, ensuring tight fit by using a bung
- switch vacuum on
- check for suction by placing hand over funnel
- put filter paper in funnel - wet with solvent used in mixture
- slowly add mixture into centre of funnel
- rinse beaker with solvent so that all crystals collect in funnel
- rinse crystals in funnel with more solvent and leave for a few mins to start to dry
what do you need for filtration under reduced pressure?
- Buchner flask
- Buchner funnel
- pressure tubing
- filter paper
- access to vacuum pump to filter
method for recrystallisation
- pour solvent into conical flask
- if flammable heat with water bath, if not use bunsen
- add sample to second beaker
- slowly add hot solvent to sample until sample just dissolves
- once dissolved, allow to cool - crystals should form
- when no more forms filter under reduced pressure to get solid
melting range
difference between temperatures at which sample starts to melt and melting is complete
if sample contains impurities…
….
range is wider
melting point is lower
preparation for melting point determination
- ensure sample completely dry
- take capillary tube and heat end in bunsen until is sealed
- allow to cool and then add sample until about 3mm deep
2 methods of melting point determination
1) electrically heated melting point apparatus
2) oil bath/Theile tube method
how does electrically heated melting point apparatus method work?
- place capillary tube w sample in sample hole
- place thermometer in thermometer hole
- use rapid heat setting - observe through magifying window
- once solid has started to melt, stop and record temp
- repeat on low setting and observe = more accurate
how does Theile tube/oil bath method work?
- set up T. tube or oil bath
- attach capillary tube to thermometer using elastic band
- insert thermometer through hole in cork (/clamp it if using oil bath)
- use micrometer to slowly heat - record temp when starts to heat
- repeat for accuracy
further purification after distillation
- pour solution into separating funnel and shake
- separate layers by tapping off
- add small amount of CaSO4 to organic layer in dry conical flask
- redistill organic layer
- collect fraction distilling at 150-156C
