16.1 Practical techniques in organic chemistry

what does a basic set of Quickfit apparatus contain

round-bottom/pear-shaped flask

receiver

screw-tap adapter

condenser

still head

why is heating under reflux used

to prepare an organic liquid without boiling odd the solvent, reactants, or products

diagram of heating under reflux

why is distillation used

to separate a pure liquid from its impurities

diagram of distillation

steps of purifying organic products

1) ensure tap of separating funnel is closed

2) pour mixture of liquids into separating funnel, place a stopper in the top of the funnel, and invert to mix the contents

3) allow the layers to settle

4) add water to mixture to identify organic layer = layer that gets bigger is the aqueous layer

5) place a conical flask under the separating funnel, remove the stopper and open the tap until the whole of the lower layer has left the funnel

6) place a second conical flask under the separating funnel to collect the other layer

how can acid impurities be removed in purifying organic products

add Na₂CO₃ (aq) and shaking the mixture in the separating funnel

any acid present will react, releasing CO₂ (g)

slowly open the tap to release gas pressure

state 3 drying agents

CaO₂

CaSO₄

MgSO₄

use of CaO₂

drying hydrocarbons

use of CaSO₄

general drying

use of MgSO₄

general drying

steps of drying an organic liquid

1) add the organic liquid to a conical flask

2) using a spatula, add some of the drying agent to the liquid and gently swirl the contents to mix together

3) place a stopper on the flask to prevent product from evaporating away. leave for 10 minutes

4) add more drying agent until some solid iss dispersed as a fine powder

5) decant the liquid from the solid into another flask

why does organic liquid have to be dried

to remove water that may be left in the organic product

why is redistillation used

to obtain just the desired organic liquid

sometimes when an organic liquid is obtained via distillation there can be traces of other liquid, especially in any liquids in the reaction vessel have a similar boiling point to the desired organic liquid

describe process of redistillation

distillation apparatus is cleaned, dried, and set up for a second distillation

aim for a narrower boiling point range