C16 - Organic Synthesis Flashcards
What is the equipment for heating under reflux?
- Round-bottom flask
- Condenser
- Rubber tubing
- Stand and clamp
- Heat source
What is reflux?
The continual boiling and condensing of a reaction mixture back to the original container to ensure that the reaction takes place without the contents of flask boiling dry.
Why is reflux used for organic reactions?
Organic reactions (compounds involving carbon) are slow and are usually flammable and volatile so have low boiling points.
Therefore if you heat them with a Bunsen burner they’ll evaporate or catch fire before they can react.
Reflux means that the liquid continuously boils, evaporates and condenses back to the flask, giving them time to react. And safer as avoids naked flames.
What is distillation?
Gently heating a mixture in a distillation apparatus, the substance will evaporate out of the mixture in order of increasing boiling point.
Equipment needed for distillation:
- Round-bottom flask
- Condenser
- Rubber tubing
- Heat source
- Stand and clamp
- Screw-cap adaptor
- Receiver adaptor
- Thermometer
- Still head
What is distillation commonly used for?
To separate a pure liquid from its impurities. As you know it’s boiling point
Why is redistillation used?
If a product and its impurities have different boiling points, then redistillation can be used to separate them. Your heating an impure product instead of a reaction mixture in distillation.
How does redistillation work?
When the liquid you want boils, you place a flask at the open end of the confessor ready to collect your product. When the the thermometer shows the tempreture is changing, put another flask at the condenser as a different liquid is about to be delivered.
What is a synthetic route?
A synthetic route shows how you get from one compound to another. It shows all the reactions with immediate products, and the reagents needed for the reaction.
What does separation do?
If a product is insoluble in water then you can use separation to remove any impurities that do dissolve in water such as water (e.g salts or alcohols).
Explain how separation works?
- Once the reaction to form a product has formed pour this into a separating funnel and add water.
- Shake the funnel and then allow it to settle. The organic layer and the aqueous layer (which contains water soluble impurities), don’t mix and separate into two distinct layers.
- You can then open the tap and run each layers into seperate containers.
What is the problem with using separation to purify a product?
The organic (desired) layer will end up containing trace amounts of water, so has to be dried.
How do you get rid of the trace of water in the organic layer in separation?
Add an anhydrous salt, like magnesium sulphate (MgSO4) or calcium chloride (CaCl2). The salt is a drying agent so binds to any water present to become hydrated.
When you first add the salt it will be lumpy however keep adding it to the solution until you swirl the mixture. Then filter the mixture to remove the solid drying agent.
What is a functional group, properties and typical reactions for an Alkane?
Functional Group - C—C
Properties - Non-polar, unreactive
Typical Reactions - Radical Substitution
What is a functional group, properties and typical reactions for an Alkene?
Functional Group - C=C
Properties - Non-polar, electron-rich double bond.
Typical Reactions - Electrophilic addition
What is a functional group, properties and typical reactions for an Alcohol?
Functional Group - C—OH
Properties - Polar C—OH bond. Lone pair on O acts as nucleophile.
Typical Reactions - Nucleophilic Substitution and Dehydration/Elimination.
