16.1 Organic Synthesis Flashcards
List the basic components of Quickfit apparatus
Round - bottomed or pear - shaped flask Receiver Screw - tap adaptor Condenser Still head
Why is reflux used?
Increases rate of reaction without boiling off the solvent, reactant or products
What apparatus do you need to heat under reflux?
Round - bottomed or pear - shaped flask Condenser Rubber tubing Stand and clamp Heat source ( usually Bunsen burner, tripod and gauze / heating mantle )
When should you use a Bunsen burner?
When reaction mixture temperature needs to be greater than 100°C
When reaction mixture contains non - flammable substances
When should you use a heating mantle?
When the reaction mixture temperature needs to be greater than 100°C
When the reaction mixture contains flammable sources
When should you use a water bath?
When reaction mixture temperature needs to be less than 100°C
When reaction mixture contains non - flammable substances
What are the stages of organic synthesis? Give examples
Synthesis ( reflux, anti-bumping granules, condsers,)
Extraction ( distillation, separatory funnel, aqueous layer test)
Purification ( sodium carbonate, drying agent, re-distillation )
When and why would you use anti-bumping granules?
Added to reaction mixture before reflux
Helps reaction mixture boil smoothly, as large bubbles cannot form and violent vibrations within glassware are reduced
When and how would you use a condenser?
Can be used during reflux / distillation
Warm vapours from reaction mixture rise out of flask.
Warm vapours enter condenser where it cools and condenses back into the flask.
Why are condensers useful?
They make it possible to continuously boil a reaction mixture without losing any reactant or product
When is it dangerous to use a condenser?
When the clamp is tightly clamped to the condenser
Or the top of the condenser is stoppered
When would you need to use distillation?
When the reaction mixture is in liquid form and :
the chemical reaction does not go unto completion
Or
by products are made concurrently
Why would you need to use distillation?
To separate unreacted substances and by products from desired product
How does distillation work?
Substance with lowest boiling point Evaporates / separates first Enters condenser Cools and condenses back into a liquid Dropping out of receiver and into a flask
When and why would you use a separators funnel?
Used when 2 visibly - distinct layers of liquids form your distillate
Used to separate the organic layer from the aqueous layer
( organic layer contains organic product, the aqueous layer is water and other water - soluble substances )
How do you use a separatory funnel ?
See that top of separatory funnel is closed and stoppered
Pour distillate into separatory funnel
Let distillate settle
Place conical flask under separatory funnel
Remove stopper and open tap on separatory funnel
Drain the bottom layer into the conical flask
Allow the top layer to remain in the separatory funnel
When and how do you do an aqueous layer tests?
Do if 2 layers appear after using a separatory funnel
Add distilled water to distillate
This means that the layer that increases in width/volume is the aqueous layer
When would you need to purify the distillate?
When the organic layer contains impurities such as :
Traces of acid
Traces of water
Organic substances ( by-products or unreacted )
What happens you purify a distillate to get rid of traces of acid?
Adding sodium carbonate to distillate removes traces of acid
This is done before extracting organic layer via separatory funnel
Acid is neutralised into a salt and water
Water produced migrates to aqueous layer
Salt produced migrates into aqueous layer
How would you purify a distillate to get rid of traces of acid?
Decant distillate into serparatory funnel
Add sodium carbonate solution to separatory funnel
Stopper separatory funnel
Invert separatory funnel
Open stopcock of the serparatory funnel
Shake the contents within with the serparatory funnel
How can you purify a distillate to remove traces of water? Give examples
Add drying agent to organic layer
Drying agent = anhydrous inorganic salt that readily takes up water
For example :
Calcium Sulfate
Calcium Chloride ( for drying hydrocarbons )
Magnesium Sulfate
When and how would you purify a distillate to remove traces of water?
Do it after extracting organic later via separatory funnel
Method:
Add drying agent to organic layer ( in conical flask)
Gently swirl contents together
Stopper the flask to prevent vaporisation
Let stand for 10min
Decant organic layer into another flask
How can you tell the organic layer is dried when purifying to remove water?
When the drying agent has dispersed into solution as a fine powder / not clumps
And the organic layer is perfectly transparent
How can you purify the distillate to remove organic impurities?
Re-distill organic layer at temperature closest to desired product’s boiling point.
The closer the observed temperature of boiling of desired product is to referenced point of the desired product the purer the distillate was.
What are some safety precautions you should take?
Apply a thin layer of grease to the ground - glass joint on the condenser to ensure it comes apart easily at the end
Clamp condenser loosely as it is fragile and easily broken
What equipment do you need for distillation?
Round bottomed or pear shaped flask Condenser Rubber tubing Heat source Stand and clamp Screw-cap adaptor Receiver adaptor Still head Thermometer
