chapter 16 organic synthesis Flashcards
Why is it important that many organic reacctions are heated under reflux
- many organic reactions occur to slowly at room temperature
- common for organic reactions to be heated to overcome the activation energy and increase the rate of reaction
Why is heating under reflux used to produce an organic liquid
- this prevents it boiling off the solvent reactants or products
Describe the procedure for heating under reflux and why each apparatus is needed
- bunsen burner use to heat the reaction mixture - allowes reaction under reflux carried out at a fixed temperature
- water bath used if reaction below 100 degrees celcius
- if heating flammable liqudis heating mantle is used - provide safety incase of appartus leak or crack
- anti bumping granules added to flask befor heating - contents boil smoothly if not use large bubbles form at bottom of liquid causing glassware to vibrate or jummp violently
- never put a stopped - otherwise a closed system will be made and pressure will build up as heated air expnded cause apparatus to explode
- water enters condenser at bottom and leaves at top to ensure outer jacket is full
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Why is heating under reflux used and how does it work
- enables liquid to be continually boiled whilst the reaction takes place
- prevents volatile components from escaping falsk and the flask from boiling dry
- the vapour form the mixture rises up the innter tine of the condenser until it meets the outerjacket containing cold water
- vapour then condenses and drips back into the flask
What is distillation
common method used to seperate a pure liquid from its impurities
Briefly describe distillation
- flask is heated and mixture in the flask will start to boil
- different liquids will have different boiling point the liquid with the lowest boiling point is most volatile
- vapour moves out of flask into other parts of apparatus
- when vapours reach fold condenser they become a liquid which drips into the collecting flask
Why do we need to purify organic liquids
- water may be obtained with the product
- top layer will be organic and bottom is aqueous / waater layer
How do we seperate the organic layer from the aqueous layers
- ensure the tap of the seperating funnel is closed
- pour the mixture of liquids into the seperating funnel and place the stopper on the top of the funnel and incert to mix the contents
- allow layers to settle
- add some water to see what layer increases in volume - the aqueou layer
- place a conical flaks under the seperating funnel remove the stopped and open the tap until whole of lower layer has left the funnel
- placre second conical flask under the seperating funnel to collet the other layer
How do you get rid of acid impurities
- by adding aqueous sodium carbonate and shaking mixture in a seperating funnel
- carbon dioxide will be produce tap needs to be slowlu opened holding the stoppeded seperating funnel upside down to release builfd up gas pressure
- aqueous sodium carbonate lauer removed and organic layer is washed with water before running both layer into seperate flasks
Why do we add drying agents to organic products
remove traces of waater
name three drying agents
- anhydrous calcium chlorice CaCL2 - drying hydrocarbons
- anhydrous calcium sulfate CaSO4 - general drying
- anhydrous magnesium sulfate - MgSO4 - general drying
Describe the procedure for drying an organic liquid
- add organic liquid to a concial flask
- add drying agnet to the liquid and swirl
- place stopper on the flask prevent prouct evaportation leave for 10 minutes
- if the solid has all stuck together in a lump there i still some water present add more drying agent until some solid is dispersed in the solution as a fine poweder
- decant the iquid from the solid into another flask if liquid is dry it should be clear
How pure is the product with a narrower boiling range
the purer the product
What is the functional group for an alkene
C=C
What is the functional group for an alcohol
-OH
