Practical Techniques in Organic Synthesis Flashcards
What types of flasks are usually used when carrying out distillation/heating under reflux?
Pear shaped or round bottom flasks
Why are bumping granules used when heating under reflux/distillation?
To prevent glassware from violently shaking/jumping when heating due to large bubbles forming
How should rubber tubing be installed on the inlet of a condenser and why?
-Water leaves at the top tube
-Water enters at the bottom tube
To ensure the entire outer jacket is full of water
What is the arrangement of tubes when heating under reflux?
-Water-out tube is furthest away/ highest up from flask.
-Water-in tube is closest to flask
What is the arrangement of tubes when heating under reflux?
-Water-out tube is closest to flask
-Water-in tube closest to the collection flask
What is used to separate aqueous liquid from an organic liquid?
Separating funnels
How do you know which layer is the aqueous layer and the organic layer when separating?
The aqueous layer is the layer that increases in volume when water is added
How do condensers works?
Cold water from the inlet of the condenser meets vapour from the heated product which condenses the vapour again.
Why is distillation used?
To purify desired product from by-products and remaining reactants
Why are thermometers needed when distilling desired product?
So you’re aware if the heat of the liquid has reached the most volatile liquid
What does volatility mean?
How readily a liquid will vapourise
What do you have to do if the preparation of your liquid involved an acid?
Add aqueous sodium carbonate, invert the mixture, then use the separating funnel to remove the NaCO3 layer
What is the risk of putting a stopper on the separating funnel when opening the tap?
Built up pressure of carbon dioxide gas
What is the reaction between an acid and a base called?
Neutralisation
Why is carbon dioxide gas released when the impure acidic liquid reacts with NaCO3?
Because when an acid and a carbonate react, carbon dioxide gas is created
What needs to be carried out if the organic liquid has a close boiling point range to an impurity?
Re-distillation for a purer product
How do you remove water left in your product?
Use a drying agent.
What are common drying agents?
-Anhydrous Calcium Chloride
-Anhydrous Calcium Sulfate
-Anhydrous Magnesium Sulfate
What is anhydrous CaSO4 and MgSO4 used?
General Drying
What is anhydrous CaCl2 used for?
Drying hydrocarbons
How do you know all the water has been removed from your product?
When the drying agent no longer lumps together and instead stays a solid powder when added
Why should you not use a stopper on the condenser?
In case the build up of pressure causes your apparatus to explode
Why should you grease your apparatus before using?
To provide a good seal and to make dismantling easy.
What would be more appropriate to use as a heat source if a reaction can take place under 100 degrees Celsius?
A water bath
What is the equipment that transfers the condensed heated liquid to a collection flask?
Receiver
How do you keep your equipment upright?
Using clamp stands.
Should you clamp your equipment loosely or firmly and why?
Loosely because the outer-jacket is fragile
What is a heat source that doesn’t use active flames?
Heating mantles
