Chapter 16 - Organic Synthesis Flashcards
(13 cards)
What is heating under reflux used for?
To prepare an organic liquid without boiling off the solvent, reactants or products
Why is a Bunsen burner used to heat under reflux?
Allows the reaction to be heated under a fixed temperature
What are anti-bumping granules used for?
Added o the liquid before the flask is heated so that the contents boil smoothly and do not make the glassware jump violently
Why do we heat under reflux?
Enables a liquid to be continually boiled whilst the reaction takes place, also prevents volatile components from escaping and the flask from boiling dry
What is the method for distillation?
- Flask is clamped by its neck and the still head is connected to the flask, still-head adaptor is T shaped and has two ground glass joints
- Grease the joints so that the apparatus come apart easily
- Attach the condenser and ensure water enters the condenser at the lowest point
- A flask is used to collect the distillate so that the distillation apparatus is not completely airtight
- Heat the flask and when the mixture boils the different liquids in the mixture will have different boiling points
- The liquid with the lowest boiling point is the most volatile and will boil first
- The vapour moves out of the flask up into the other parts of the apparatus, leaving behind the less volatile components
- When the liquid reaches the cold condenser they condense and become lisos which drips into the collecting flask
How do we purify organic products?
- Ensure that the tap of the separating funnel is closed
- Pour the mixture of liquids into the separating funnel, place a stopper in the top of the funnel, and invert to mix the contents
- Allow the layers to settle
- Add some water to see which layer increases in volume - this is the aqueous layer
- Place a conical flask under separating funnel, remove the stopper and open the tap until the whole lower layer has left the funnel
- Place a second conical flask under the separating funnel to collect the other layer
- You will now one conical flask containing the organic layer and another containing the aqueous layer
How can we remove acid impurities from the organic product?
Adding aqueous sodium carbonate and shaking the mixture in the separating funnel
Any acid present will react with sodium carbonate and release carbon dioxide
How do we dry the organic product?
Add a drying agent (anhydrous salt)to the organic liquid
What are common drying agents?
Anhdryous calcium chloride - drying hydrocarbons
Anhydrous calcium sulfate - general drying
Anhydrous magnesium sulfate - general drying
What is the method for drying an organic liquid?
- Add the organic liquid to a conical flask
- Using a spatula, add some of the drying agent to the liquid and gently swirl the contents to mix together
- Place a stopper on the flask to prevent your product from evaporating away (leave for 10 mins)
- If the solid has all stuck together in a lump, there is still some water present. Add more drying agent until some solid is dispersed in the solution as a fine powder
- Decant the liquid from the solid into another flask. If the liquid is dry it should be clear
What is redistillation?
When organic liquids may still contain impurities as they have similar boiling points they are redistilled
What is organic synthesis?
Preparation of complex molecules from simple starting materials
What are target molecules?
Described the compound that a chemist is attempting to prepare by organic synthesis
