Chapter 16 - Organic synthesis Flashcards
What 5 elements make up the quick-fit apparatus?
Pear-shaped flask Receiver Screw-tap adaptor Condenser Still head
Why is it advantageous to heat a material under reflux?
If you heat organic reactants, they’ll evaporate before they can react
It also avoids the use of a naked flame
What does it mean to heat a reactant under reflux?
The mixture is heated in a flask with a vertical Liebig condenser, which continuously boils, evaporates and condenses the vapours
What five pieces of kit are needed to heat under reflux?
Pear-shaped flask Condenser Rubber tubing Stand with clamp Heat source
How do you heat a mixture under reflux?
Set up your apparatus
Add the reaction mixture, along with some anti-bumping granules, to the flask
Apply a layer of grease to the joint on the condenser, to ensure the equipment can be dismantled at the end
Connect the rubber tubing to a water outlet
What do anti-bumping granules do?
They allow the contents to boil smoothly
Why is it important never to put a bung in the top of the condenser?
There would be too much pressure building up and the apparatus may explode
In what way should water enter the jacket?
Enter at the bottom and leave at the top
What is distillation used for?
Separating substances with different boiling points
What nine pieces of equipment are needed for distillation?
Pear-shaped flask Condenser Rubber tubing Heat source Stand and clamp Screw-tap adaptor receiver adaptor Still head Thermometer
How do you heat a mixture under reflux?
Set up your apparatus and grease the joints of still head
Connect rubber tubing to a water outlet
Heat your mixture. The chemicals with the lowest boiling points will evaporate and be collected in the flask first
The vapour will move out of the flask and into the condenser, where it will condense and drip into the receiver flask
Why might you need to purify the mixture obtained from distillation or refluxing?
It might contain water
How do you purify a mixture?
1) Add some water to your mixture. The layer that increases in size is the aqueous layer (we don’t want this)
2) Pour the mixture into a separating funnel, ensuring the tap is closed
3) Place a bung in the top and invert to mix the contents
4) Allow the layers to settle
5) Place a flask under the tap, remove the stopper and run out the entire bottom layer into the flask
6) Run off the other layer into another flask
7) Discard the aqueous layer - your organic product is now purified
How would you remove acid impurities?
Add sodium carbonate and shake whilst in the separating funnel
The tap must be slowly opened, whilst holding the stoppered funnel upside down, to release any CO2 formed by the gas
Remove the sodium carbonate layer and repeat the normal method
What is anhydrous calcium chloride used for?
Drying hydrocarbons
What is anhydrous calcium sulfate used for?
General drying
What is anhydrous magnesium sulfate used for?
General drying
How do you dry an organic liquid?
Use a spatula to add some of the drying agent to the liquid and swirl to combine
Place a stopper in the flask to prevent the liquid evaporating and leave for ten minutes
If the solid has clumped together, there is still some water present, so add some more of the drying agent until the solid disperses
Decant the liquid from the solid into another flask
Why might you have to carry out redistillation?
Organic liquids have substances that are very close in boiling point
How do you carry out redistillation?
Carry out the distillation as normal but this time, only collect the product with the boiling point of the compound you are trying to make
How do you get a carboxylic acid?
Heat a primary acid under reflux with acidified potassium dichromate
How do you get an aldehyde?
Distil a primary alcohol with acidified potassium dichromate
How do you get a ketone?
Heat a secondary alcohol under reflux with acidified potassium dichromate
What is produced when you react an alcohol with sodium halide and sulfuric acid?
A haloalkane
What is produced when you react a haloalkane with sodium hydroxide under reflux?
An alcohol
What is produced when you create an alcohol with concentrated sulfuric acid?
An alkene
What is produced when you react an alkene with steam and a H3PO4 catalyst?
An alcohol
What is produced when you react an alkene with hydrogen halide?
A haloalkane
What is produced when you create an alkene with hydrogen and a nickel catalyst?
An alkane
What is produced when you react an alkane with a halogen under UV light?
A haloalkane
What does a synthetic route tell you?
How you get from one compound to another
What must you include when asked how to make a chemical?
Any special procedures and the conditions needed
What is a target molecule?
The compound that a chemist is trying to make by organic synthesis
What are the three steps to describing organic synthesis?
Identify the functional groups in your starting and target molecules
Identify the intermediate linking these two
State the reagents and conditions needed for each step
Which of the compounds we have studied have polar bonds?
Alcohols - C-OH
Haloalkanes - C-X
Aldehydes/ketones - C=O
What reactions will alkanes typically undergo?
Radical substitution
What reactions will alkenes typically undergo?
Electrophilic substitution
What reactions will carboxylic acids typically undergo?
Esterification
What reactions will aldehydes typically undergo?
Oxidation
What reactions will haloalkanes typically undergo?
Nucleophilic substitution
What reactions will alcohols typically undergo?
Nucleophilic substitution, dehydration/elimination
Alcohol - ketone
Reflux secondary alcohol with H2SO4/K2Cr2O7
Alcohol - carboxylic acid
Reflux primary alcohol with H2SO4/K2Cr2O7
Alcohol - aldehyde
Distil primary alcohol with H2SO4/K2Cr2O7
Alcohol - alkene
Conc. H2SO4
Alkene - alcohol
Steam with H3PO4
Alkene - alkane
H2 + Nickel
Alkane - haloalkane
Halogen + UV
Alkene - haloalkane
Hydrogen halide
Alcohol - haloalkane
Sodium halide + H2SO4
Haloalkane - alcohol
NaOH + reflux
