16 - Organic synthesis Flashcards
quick fit apparatus contains
- round bottom flask
- receiver
- scre tap adaptor
- condenser
- still head
how to identify the organic layer when purifying organic products
- there are two layers, the aqueous/water layer and the organic layer
- adding water to the mixture
- the layer that gets bigger is the aqueous layer
how to purify organic products
use a separating funnel
1- ensure tap of the funnel is closed
2- poor the mixture in the funnel, place a stopper at the top, and invert to mix the contents
3 - allow the layers to settle
4 - at water to identify the aqueous layer
5 - place a conical flask under the funnel, remove the stopper and open the tap until the whole of the lower layer has left
6 - place a second conical flask under to collect the other layer
how to purify organic products that may contain acidic impurities
- impure product may contain acid
- remove this by adding sodium carbonate and shaking the mixture in the separating funnel
- any acid reacts with it releasing CO2 gas
- the tap needs to be slowly opened and hold the funnel upside down to release the gas
Drying organic product
1 - add organic liquid to conical flask
2 - using a spatula add some of the drying agent to the liquid and gently swirl the contents to mix together
3 - place a stopper on the flask to prevent product from evaporating, leave for ten mins
4 - if the solid is stuck in a clump, there is still water there, add more of the drying agent until its a fine powder
5 - decant the liquid from the solid into another flask,
what is a drying agent
an anhydrous inorganic salt that readily takes up water to become hydrated
anhydrous calcium chloride
anhydrous calcium sulphate
Solvent Extraction
- a purification technique used when both a compound and its impurities are soluble in water but have different solubilities in an organic solvent.
- Add the impure compound to a separating funnel. An aqueous solution of the impure compound gets added a separating funnel.
- Add some organic solvent. Shake well. The product will dissolve in the organic compound and the impurities will be left dissolved in the water.
- Two layers form. The organic solvent and water are immiscible so two layers will form in the separating funnel: the top layer containing the product dissolved in the organic solvent, and the bottom layer containing the impurities dissolved in water.
- Let the layers run off separately. Each layer is run off into different containers. As the impurities are on the bottom layer, they will get run off first.
Gravity Filtration
Gravity filtration is used to keep the filtrate.
A piece of flutter filter paper is placed on a funnel, which then gets fitted into a conical flask.
The mixture is poured gently into the filter paper. The solid will remain on top whilst the liquid is able to pass through and collect into the flask.
Filtration Under Reduced Pressure
- filterer paper
- buchner funnel
- buchner flask
- vacuum pump
The vacuum gets turned on and the mixture is poured into the Büchner funnel.
As a result of the reduced pressure inside the flask, the liquid gets sucked out of the mixture and down the funnel into the flask. The solid is left behind on the filter paper.
Recrystallisation
Recrystallisation is used to purify solid organic products.
- Add hot solvent. Add just enough solvent to produce a saturated solution of the impure compound.
- Filter the hot solution. Remove insoluble impurities by using gravity filtration.
- Let the solution cool. As the solution cools down, the solubility of the compound decreases.
- Crystals form. As the solubility of the compound decreases, crystals start to form. As the concentration of impurities is much lower, they take longer to from crystals and hence will remain in solution.
- Remove the crystals. The crystals are removed by using filtration under reduced pressure and then rinsed with cold solvent. Finally they are let dry.
Refluxing
The rate of reaction of organic reactions tends to be slow unless the reaction mixture gets heated up.
However, organic compounds also tend to be highly flammable and have low boiling points, which means that if heated with an open flame, they are likely to evaporate or burn before a reaction can take place.
Instead, the reacting mixture in organic reaction is heated under reflux.
The flask containing the reaction mixture is connected to a vertical Liebig condenser. As a result, any reactants that boil off will immediately condense and fall back into the flask so that the reaction can continue
synthesis of a haloalkane
preparation
seoaration
distilation
alkene -> alkane
H2
Ni catalyst
alkene -> haloalkane
hydrogen halide
