4.2.3 Organic Synthesis Practical Skills Flashcards
Describe how a Quickfit apparatus is connected
Grease the joints using some petroleum jelly on the inside of the joints before connecting the pieces together
In a distillation setup, why is it necessary to have a continuous water flow around the condenser?
So that the water remains cool in order for the mixture to be distilled
Describe a method that can be used to separate immiscible liquids
Pour the mixture into a separating funnel and some distilled water,
Add the stopped and invert the flask to mix the mixture
Equalise the pressure by opening the stopper as required
Continue shaking until there is no “whistle” sound
To collect the water in the lower layer, open the stopper and place a beaker under the spout
Use another beaker to collect the desired organic layer
Shake the liquid with some drying agent
Name two drying agents
Magnesium sulphate
Calcium chloride
How to use drying agents
Add a selected drying agent to the organic product
If the drying agent forms clumps, add some more until they are moving freely
Use gravity filtration to collect the dry product
Filtrate is the product
What does re-distillation mean?
When a liquid is purified by using multiple distillations
How can unsaturated hydrocarbons be tested?
What are the observations?
Use bromine water
Add a few drops of bromine water to the sample and mix well
Positive test - the bromine water turns colourless
What are the reagents used to test haloalkanes and what are the observations?
Reagents: silver nitrate, ethanol and water
Observations:
Chloro: white precipitate
Bromo: cream precipitate
Iodo: yellow precipitate
What are the 3 reagents that can be used to test carbonyls?
Acidified potassium dichromate
Fehling’s solution
Tollens’ reagent
What are the observations when acidified potassium dichromate reacts with ketones and aldehydes?
Aldehyde: turns from orange to green
Ketones: no change
What are the observations when Fehling’s solution is reacted with ketones and aldehydes?
Aldehydes - dark red precipitate
Ketones - no change
What are the observations when Tollens’ reagent is reacted with ketones and aldehydes?
Aldehydes - silver mirror precipitate
Ketone - no silver mirror, no precipitate
What are the reagents that can be used to test carboxylic acid?
What are the corresponding observations?
Universal indicator - pH of weak acid
Reactive metal - hydrogen effervescence
Metal carbonate - carbon dioxide effervescence
