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Module 4 - Chapter 16 - Organic synthesis I - Coggle Diagram
Module 4 - Chapter 16 - Organic synthesis I
Purifying organic products
If water is obtained along with the product, you'll see two liquid laters inside your collection flask
If you aren't sure which is the organic layer, add some water, and the layer that gets bigger is water
Separation
Ensure the tap of the separating funnel is closed
Pour the mixture into the seperating funnel, place a stopper in the top of the funnel,and invert to mix the contents
Once they've settled, add some water to see which layer increase in volume
Place a conical flask under the seperating funnel, remove the stopper and open the tap until the whole of the lower layer has left the funnel
Place another conical flask under to collect the other layer
Label to flasks that contain the organic and aqueous layer
Removing acid impurities
Impure products may contain acid impurities
Adding aqueous sodium carbonate and shaking the mixture in the seperating funnel
Acid present reacts with sodium carbonate to release CO2
Tap is slowly opened holding the stoppered separting funnel upside down to release gas pressure
Aqueous sodium carbondate layer is removed and the organic layer washed with water
Drying the organic product
Removed by adding a drying agent to the organic liquid
Drying agent is an anhydrous salt that readily takes up water to become hydrated
Examples - anhydrous calcium chloride/ calcium sulfate
Procedure
Add organic liquid to a conical flask, and add a spatula of the drying agentto the liquid and swirl
Place a stopped on the flask to prevent your products from evapourating away
If the solid has stuck together in a lump, there is still some water, so add more drying agent until some solid is dispered in the solution as a fine powder
Decant the liquid from the solid into another flask
Redistillation
Organic liquids may have close boiling points, so your sample may still contain some organic impurities
Distillation apparatus is cleaned and dried and set up again so that a second distillation can be carried out
Only collect the product with the boiling point of the product you're trying to make
Narrower boiling range, the purer the product
Synthetic routes
Target molecules
Used to describe the compound that the chemistry is attempting to make
Simple synthesis - target molecule can be obtained by reacting a readily available starting material with a readily available reagant in a one step reaction
Two stage synthesis
Identify the functional groups in your starting molecules
Identify the intermediate links to the starting and target molecules
State the reagents and conditions for each step
Ozonolysis
Used to break open a C=C double bond
Reaction is useful to prepare aldehydes and ketones
Idenity functional groups
Test for unsaturation - bromine water
Test for 1st.2nd alcohols - acidified potassium dichromate
Test for aldehydes - tollen's reagent
Test for haloalkanes - aquous silver nitrate with ethanol
Boiling point determination
Purer the substance, the closer its boiling point to the true value
Substance is packed into a Thiele tube which has an inverted capillary tube in it
Substance is heated above its boiling point and allowed to cool
When it condenses into a liquid, it will be drawn into the capillary tube and the temperature this happens at is the boiling point