5.4.3 Organic Synthesis Flashcards
(33 cards)
What is the purpose of refluxing?
To ensure you don’t lose volatile organic substances.
What is the purpose of anti-bumping granules?
To make the boiling of a substance smoother.
Why do volatile organic compounds need to be refluxed?
They’ll evaporate or catch fire before they have time to react.
How would you set up apparatus for refluxing?
Attach a Liebig condenser to a round bottomed flask. Ensure the water enters the condenser at the bottom.
How does the reflux setup work?
It condenses the vapours, recycling them back into the round bottommed flask.
Why does water have to enter a Liebig condenser from the bottom?
To ensure the Liebig condenser is full of cold water.
Why might you want to “wash” an organic product with sodium hydrogen carbonate solution?
To remove any excess acid.
How would you extract the waste product of a reaction from a mixture after washing it with sodium hydrogen carbonate solution.
Use a separating funnel.
Explain the process of solvent extraction.
You can separate a product from a mixture by dissolving it in a solvent. Shake the mixture with fresh solvent several times to extract as much product as possible.
Give an example of a drying agent.
Anhydrous calcium chloride.
When would you “dry” the products of an organic reaction.
When water is produced or used.
Explain the process of drying a mixture with anhydrous calcium chloride.
It removes water from the mixture by forming solid crystals which can be filtered off.
What does recrystallisation achieve?
It allows you to remove a small amount of impurity in a solid.
Outline the process of recrystallisation.
Add very hot solvent to the impure solid until it just dissolves. Cool the solution slowly to form crystals of the product. Remove the solution of impurities by filtration and washing with ice-cold solvent.
What must be considered when choosing a solvent for recrystallisation?
The product should be very soluble in hot solvent but nearly insoluble in cold solvent.
Why should a minimum amount of hot solvent be added during recrystallisation?
To avoid losing product in the solution and therefore maximise yield.
What does melting a boiling point indicate about the purity of products?
If products are impure, melting point is lowered and boiling point is raised. If a product is very impure, melting a boiling will occur across a wide range of temperatures.
How would you accurately measure boiling point of a product?
Measure the temperature that the liquid is collected at during distillation.
How would you accurately measure melting point?
Place a small amount of the solid in a capillary tube and place it in a beaker of oil with a very sensitive thermometer. Slowly heat and stir until it dissolves and record temperature when it does.
What does fractional distillation do?
Separate multiple liquids with different boiling points.
Explain the equipment used for fractional distillation.
A round bottomed flask with glass beads in a fractionating column. A Liebig condenser is connected to the column next to a thermometer to measure the temperature at that point.
How does fractional distillation work?
As temperature rises, different compounds reach the top of the column, deepening on their boiling point.
Give one disadvantage of standard fractional distillation.
The high temperatures may cause a reduct to decompose.
Explain the process of steam distillation.
Steam is passed into the mixture to lower the boiling point of the product so that it evaporates at a temperature that doesn’t cause it to decompose.
