distillation + reflux

diagram

purpose of distillation

• separate a mixture of liquids with different boiling points

• prepare an organic liquid - and immediately separate it.

reagant for distillation

• potassium dichromate with conc h2so4

conditions

• use a limited amount of dichromate and warm gently and distil out the aldehyde as it forms

why do you use antibumping granules?

• to allow smooth boiling by forming smaller bubbles - prevent splashing up the sides of the flask due to bubbles caused by vapours

• provides a larger surface area so that smaller, more controlled bubbles can form

condenser - why must water come in at the bottom and leave at the top

• water fills the condenser fully -

• condenser cold enough

• condense… gas → liquid

how to maximise product yield

• heat around boiling point (don’t go too close to boiling point of other substances in the mixture)

• place collection vessel in beaker of ice cold water - to keep the product condensed (as product is volatile - minimise the loss of vapours)

reflux diagram

when is reflux used?

• used for heating organic reaciton mixtures for long periods eg. for full oxidation of alcohol to carboxylic acid

• condenser prevents organic vapours from escaping by condensing them back into liquids

what should you remember when drawing reflux

• no lines between condenser and flask

• dont have top of condenser sealed

why use a heating mantle and not bunsen burner

• organic substances are flammable - important to have no naked flames

principle of reflux

• a mixture of liquids is heated to their boiling point for a prolonged time

• vapour is formed which escapes from the liquid mixture

• vapours cool and condense back into liquid

• return to liquid mixture

why must the reflux apparatus must not be fully sealed?

• prevents pressure build up