4.2.3 Organic Synthesis Flashcards
what is distillation used for
to separate an organic product from its reaction mixture
collect distillate at approximate boiling point of range of desired liquid
what apparatus is used to set up distillation apparatus
round-bottom flasks
leibig condenser
bunsen burner
thermometer
example of an AS level reaction using distillation
primary alcohol -> aldehyde
reagent: potassium dichromate (VI) and dilute sulfuric acid
conditions: use small amount of dichromate, warm gently and distil out aldehyde as it forms to prevent further distillation
observation: orange dichromate solution changes to green due to the Cr3+ ions in solution
why don’t you seal the end of a condenser in reflux reactions
build up of gas pressure could cause apparatus to explode
apparatus needed to set up reflux apparatus
vertical condenser (isn’t sealed)
round bottom flask
electrical heater
example of an AS level reaction using reflux
primary alcohol -> carboxylic acid
reagent: potassium dichromate (VI) and dilute sulfuric acid
conditions: use an excess of dichromate, and heat under reflux: (distil off product after the reaction has finished using distillation set up)
observation: orange dichromate turns green due to the Cr3+ ions
what is added to the reflux and distillation apparatus
anti-bumping granules
why are anti-bumping granules added
to prevent vigorous uneven boiling by making small bubbles form instead of large ones
why are electrical heaters used to heat organic chemicals
because organic chemicals are highly flammable and could easily set on fire with a naked flame
purifying an organic liquid apparatus
separating funnel
how do you purify an organic liquid
put distillate of impure product into the separating funnel
wash by adding:
-sodium hydrogencarbonate solution, shaking and releasing pressure from CO2 produced
-saturated sodium chloride solution
allow layers to separate in funnel then run and discard the aqueous layer
-run the organic layer into a clean, dry conical flask and add three loads of drying agent (anhydrous sodium sulphate, calcium chloride) to dry the liquid, when dry the liquid should appear clear
-decant liquid into distillation flask
-distil to collect the pure product
why is sodium hydrogencarbonate used when purifying an organic liquid
to neutralise any remaining reactant acid
why is sodium chloride used when purifying an organic liquid
to separate the organic layer from the aqueous layer
when purifying an organic liquid describe the upper layer
layer with lower density
normally the organic layer
what should the drying agent properties be
insoluble in the organic liquid
not react with the organic liquid
