Organic Synthesis Flashcards
Drying agents that can be used to remove water from an organic product
-Anhydrous CaCl2 (drying hydrocarbons)
-Anhydrous CaSO4
-Anhydrous MgSO4
Heating Under Reflux Apparatus
-Round bottom or Pear shaped flask
- Condenser ( lid = explosion bc pressure)
- Rubber tubing
- Stand and Clamp
- Heat source
Why are anti bumping granules used?
Prevents liquid from jumping out of glassware or vibrating violently.
Why is heating under reflux important?
Prevents volatile compounds from escaping
Distillation
Liquid is boiled to a vapour that is then condensed into a liquid, liquid with the lowest boiling point is the most volatile and will boil first.
Why is petroleum jelly used in these apparatus?
To stop things from getting stuck
Purifying organic liquids
-Add mixture to separating funnel then add sodium carbonate to neutralise excess acids
-Add water and layer that gets bigger is the aqueous layer
-Organic layer is at the top
- Allow aqueous layer to run out and collect organic layer
-Add drying agent e.g anhydrous CaSO4/CaCl2
-Can redistill if you have multiple organic products at 44•C
Alkane to Haloalkane
Halogen, UV light
Alkene to Haloalkane
Hydrogen Halide (HX)
Alcohol to Haloalkane
Sodium halide (NaX) and H2SO4 under reflux
Haloalkane to Alcohol
NaOH (aq) under reflux
Alkene to Alkane
H2, Ni catalyst
Alkene to Alcohol
h2O(g), H3PO4 catalyst
Alcohol to alkene
Conc H2SO4 under reflux
Primary alcohol to Carboxylic acid
K2Cr2O7, H2SO4 under reflux
Secondary alcohol to ketone
K2Cr2O7, H2SO4 under reflux
Primary alcohol to aldehyde
K2Cr2O7, H2SO4 under distillation
Why should water enter at the bottom of the condenser?
So that the condenser fills with water and promotes efficient cooling
Purification of organic solids
- Recrystallise the impure solid by dissolving in the minimum amount of hot solvent (e.g water)
- Cool to allow crystallisation to occur then filter under reduced pressure using Buchner apparatus
- Wash the purified aspirin using cold water and dry
Ways of checking purity
Melting point and TLC
Checking purity using melting point
-Measure melting of sample using melting point apparatus
- Compare to data value
- Impurities lower melting points and widen the melting range
- The purer the sample, melting occurs closer to the true value and over a narrow range (2.C)
Checking purity using TLC
-Run chromatogram of impure sample
- Calculate Rf value
- Compare to a known data base
- Or compare to a known pure chromatogram
