Synthesis Flashcards
(8 cards)
Example Question: Suggest a 2 stage synthesis for the preparation of propan-1-al from 1-chloropropane including any reagents and conditions required.
1-chloropropane —NaOH(aq) reflux—> Propane-1-ol —acidified dichromate distillation—> Propane-1-al
Haloalkane ————————————-> 1’ alcohol ——————————————————> aldehyde
use the map but need to learn the map
focus on what changes
What is the name of the apparatus needed to carry out organic preparation and what are the names of the pieces?
Quickfit Apparatus:
- Pear-shaped flask
- Still head
- Liebig condenser
- Screw-tap adaptor
- Receiver Adaptor
Why is heating under reflux used and what source of heat is used and why?
Heating under reflux used to heat mixture without boiling off the solvent, enables liquid to be continually boiled whilst reaction takes place, preventing the reaction vessel from boiling dry.
A bunsen can be used to heat if its non-flammable otherwise beaker of water is used if flammable.
Why is distillation used?
Distillation used to separate pure product from a mixture after it has been heated under reflux. Separating technique based on the boiling point of components (liquid with lowest bp distillation 1st)
How do you separate and purify organic liquids?
Observe 2 layers inside collection flask (1 organic and 1 aqueous layer which contains water). They can be separated using a separating funnel.
To separate first allow the 2 layers to settle (1 will be more dense than the other, more dense will go to the bottom water has density 1gcm3). Then add water to know which is the aq layer as it would grow.
To remove water from the organic product add a drying agent of anhydrous magnesium sulphate.
Redistill (quote bp in question in answer*)
Exam question: Student obtains mixture containing organic layer (1.27gcm-3) and aq layer (1gcm-3). Draw labelled diagram to show how safely set up apparats for preperation. And outline method to obtain a pure sample of 1-bromobutane from reaction mixture.
Apparatus set up for reflux: pear shaped flask, Heat source, Condenser (water in at bottom + out at top)
Purification: use separating funnel to separate organic and aq layer(collect lower organic layer as density greater than aq layer). Add drying agent of an anhydrous salt (anhydrous MgSO4), redistillation (collect fraction distilling at 102’C
How would using 1-chloropropane, rather than 1-bromopropane affect the overall atom economy of this reaction?
It would increase the atom economy as Cl has a smaller relative atomic mass than Br.
Suggest how a thermometer used in distillation would allow to check the purity of product?
Its used to check that the temp is kept at the bp of the product.
