4.2.3 Organic Synthesis Practical Skills Flashcards
Describe how a Quickfit apparatus is connected.
- Grease the joints using petroleum jelly on the inside of the joints
- Connect 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
- Ensures the mixture can be distilled effectively
Describe a method that can be used to separate immiscible liquids.
- Pour the mixture into a separating funnel and add distilled water
- Add the stopper 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 lower water layer, open the stopper and place a beaker under the spout
- Use another beaker to collect the desired organic layer
- Shake the liquid with a 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 more until they move freely
- Use gravity filtration to collect the dry product
- The filtrate is the product
What does re-distillation mean?
- Purifying a liquid 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: bromine water turns colourless
What are the reagents used to test haloalkanes, and what are the observations?
- Reagents: silver nitrate, ethanol, 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?
- Ketones: no change
- Aldehydes: turns from orange to green
What are the observations when Fehling’s solution is reacted with ketones and aldehydes?
- Ketones: no change
- Aldehydes: dark red precipitate
What are the observations when Tollens’ reagent is reacted with ketones and aldehydes?
- Ketones: no silver mirror
- Aldehydes: silver mirror
What are the reagents that can be used to test carboxylic acids? What are the corresponding observations?
- Universal indicator: pH of weak acid
- Reactive metal: hydrogen effervescence
- Metal carbonate: carbon dioxide effervescence
