Organic Synthesis Flashcards
what are the basics set of quickfit apparatus
round bottom or pear shaped flask
receiver
screw tap adapter
condenser
still head
how can we heat organic reactions
it is common for reactions to be heated to overcome activation energy and increase rate of reaction.
Heating under reflux common procedure used to prepare an organic liquid without boiling of the solvent reactants or products
what are apparatus needed to heat under relux
round bottom or pear shaped flask
condenser
rubber tubing
stand and clamp
heat source(usually a Bunsen burner, tripod and gauze or a heating mantle)
why is a mantle used
for heating flammable liquids a heating mantle can be used so that there is no naked flame present
provides an added level of safety if any of the apparatus cracks or leak
how to conduct reflux experiment
1)flask clamped by its neck. Before fitting in the condenser you need to add reaction mixture and anti-bumping granules to the flask
2)Finally apply a thin layer of grease to the ground glass joint of the condenser.
3)Place the condenser safely into the flask and gently rotate the condenser back and forth to provide a good seal and ensure that the apparatus comes apart easily at end of experiment
why do you need add antibumping granules to the liquid before flask is heated
so contents boil smoothly. If not used large bubbles will form at the bottom of the liquid and make glassware vibrate and jump easily
During reflux how should the condenser be positioned and clamped
up right
clamped loosely because glass outer jacket is very fragile and easily broken
do we put a topper on the condenser
no you would have a closed system and pressure would build as heated air expands up causing the apparatus to explode.
what is the rubber tubing used for in reflux
connect inlet of the condenser to the tap and outlet to the sink. Water enters condenser from the bottom and leaves from the top to ensure outer jacket is full
What does heating under reflux enable liquid to do
and what does this prevent
to be continually boiled while reaction takes place
prevents volatile components from escaping and the flask from boiling dry.
what is distillation
common method to seperate pure liquids from its impurities
what apparatus needed for distillation
round bottom or pear shaped flask
condenser
rubber tubing
heat source
stand and clamp
screw-cap adapter
receiver adapter
still head
thermometer
how to setup distillation
flask is clamped by its neck and still head connected to the flask. The still head adapter is T shaped and has two ground-glass joints, one to fit the screw-cap adapter and one to fit the condenser.
2)a second clamp placed round the receiver adaptor at the point at which it is attached to the condenser
.Thos removes the need to clamp the condenser as it will be supported efficiently at both ends
3)as with reflux the rubber tubing is used to connect the inlet of the condenser to tap and outlet to sink. Water always enters the condenser at the lowest point.
4)flask used to collect the distillate so that the distillation apparatus is not completely air tight.
why should we grease the joints of the appparatus
so it comes of easily
how to conduct distillation
Once apparatus setup the flaks is heated and mixture in flask will start to boil.The different liquids will have differnt boiling points. The liquid with the most boiling point is the most volatile and will boil first
2)The vapour moves out of the flask up into the other parts of the apparatus leaving behind the less volatile components of the mixture. When the vapours reach the cold condenser they condense and become liquid. This liquid then drips into condenser flask.
how can you tell if you have to purify an organic layer
you will see two liquid layers inside your collection flask
one with organic layer and one with aqueous or water layer
How to identify organic layer
add some water to your mixture . The layer that gets bigger is the aqueous solution
How to purify organic products
1) ensure tap of the separating funnel is closed
2)Pour the mixture of liquids into separating funnel and place a stopper in the top of the funnel and invert to mix the contents
3)Allow the layers to settle
4)Add some water to see which layer increase in volume - this is the aqueous layer
5)Place a conical flask under the separating funnel remove the stopper and open the tap until whole of the lower layer has left the funnel.
6)Place second conical flask under separating funnel to collect the other layer
7)You will now have one conical flask containing organic layer and another containing aqueous layer. label flask
how to remove acid impurities in impure product
adding aqueous sodium carbonate and shaking the mixture in the separating funnel
Any acid present will react with sodium carbonate and releasing carbon dioxide gas. The tap needed to be slowly opened, holding the stoppered separating funnel upside down to release any gas pressure that may build up
Finally the aqueous sodium carbonate layer is removed and the organic layer washed with water before running both layers off into two separate flasks
What is a drying agent
is an anhydrous inorganic salt that readily takes up water to become hydrated.
What are common drying agents
anhydrous chloride CaCl2 use drying hydrocarbons
anhydrous calcium sulfate CaSO4 General drying
anhydrous magnesium sulfate ,MgSO4 use for General drying
Whats the procedure for drying an organic liquid
1)Add the organic liquid to a conical flask
2)Using a spatula, add some of the drying agentto the liquid and gently swirl the contents to mix together
3)Place stopper on the flask to prevent your product from evaporating away. Leave for about 10 minutes
4)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
5)Decant the liquid from the solid into another flask. If the liquid is dry it should be clear
why does redistillation occur
Sometimes organic liquids have boiling points that are relatively close together so your prepared sample may still contain some organic impurities
what occurs in redistillation
distillation apparatus is cleaned and dried and set up again so that second distillation can be carried out. This time only collecting the product with the boiling point of the compound your trying to make. The narrower the boiling range the pure the product. You will now have separated your product from any impurities
What are compounds used for as drying agents
Anhydrous calcium chloride drying hydrocarbon
Anhydrous calcium sulfate
Anhydrous magnesium sulfate
Why does gas not leave in reflux reaction
The vapour from mixture rises up the inner tube of the condenser until it meets the outer jacket containing cold water.the vapour then condenses and drips back into flask
What happens once apparatus set up in distillation
Flask heated and the mixture in the flask will start to boil.The different liquids in the mixture will have different boiling points. The liquid with the lowest boiling point is most volatile and boil first
