Organic practicals 5

Draw labelled distillation apparatus

Explain why we use anti bumping granules

Create smaller bubbles

Explain why we use bung distillation

Closed system

Prevent gases of product escaping

Allows collection

Which direction should water be added

Water in at bottom

Out at top

Why do we add water at the bottom

So condenser is fully filled with water

So condenser fully cool

So product can condense

SAFTEY concern s reflux

Round bottom flask not clamped

Bung-build up of pressure

Suggest why a water bath is better than direct heating with a Bunsen burner

Alcohol/organic product

Flammable

Draw labelled reflux apparatus

What can acidified potassium dichromate be used to distinguish between

-primary alcohols

Secondary alcohols

Aldehydes

Expected observation when oxidising with acidified potassium dichromate

Orange to green

What can tollens reagent be used to distinguish and observations

Aldehyde

Silver mirror

How can you distinguish between two primary alcohols

comapre to known database

Have different fingerprint regions

Why might mass spectrometry using electrosoray ionisation not be a suitable method of distinguishing between isomers

They have the same precise mr

What can you use to test for a carboxylic acid

Sodium carbonate

Produce co2 effervescence

Outline method used for recrystallisation

• Dissolve product in minimum volume of hot solvent -create saturated solution

• Hot filtration to remove soluble impurities

• Cool to recrystallise

• Filter under reduced pressure

• Wash with cold solvent and dry-between two pieces of filter paper

Explain why:

Flask cooled to room temp before crystals filtered off

Crystals were compressed in funnel

Cold water was poured through crystals

Yield lower if warm

Air passes through sample so better drying

Wash soluble impurities

Outline how you would show recrystallised product is pure

Measure melting point

Using mp apparatus

Match mp to data boom

Suggest two reasons why recrystallised product % yield is not 100%

Sample lost during recrystallisation

Sample still wet.