16 - Organic synthesis

Question 1

quick fit apparatus contains

Answer 1

• round bottom flask
• receiver
• scre tap adaptor
• condenser
• still head

Question 2

how to identify the organic layer when purifying organic products

Answer 2

• 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

Question 3

how to purify organic products

Answer 3

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

Question 4

how to purify organic products that may contain acidic impurities

Answer 4

• 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

Question 5

Drying organic product

Answer 5

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,

Question 6

what is a drying agent

Answer 6

an anhydrous inorganic salt that readily takes up water to become hydrated

anhydrous calcium chloride
anhydrous calcium sulphate

Question 7

Solvent Extraction

Answer 7

• a purification technique used when both a compound and its impurities are soluble in water but have different solubilities in an organic solvent.

1. Add the impure compound to a separating funnel. An aqueous solution of the impure compound gets added a separating funnel.
2. Add some organic solvent. Shake well. The product will dissolve in the organic compound and the impurities will be left dissolved in the water.
3. 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.
4. 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.

Question 8

Gravity Filtration

Answer 8

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.

Question 9

Filtration Under Reduced Pressure

Answer 9

• 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.

Question 10

Recrystallisation

Answer 10

Recrystallisation is used to purify solid organic products.

1. Add hot solvent. Add just enough solvent to produce a saturated solution of the impure compound.
2. Filter the hot solution. Remove insoluble impurities by using gravity filtration.
3. Let the solution cool. As the solution cools down, the solubility of the compound decreases.
4. 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.
5. Remove the crystals. The crystals are removed by using filtration under reduced pressure and then rinsed with cold solvent. Finally they are let dry.

Question 11

Refluxing

Answer 11

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

Question 12

synthesis of a haloalkane

Answer 12

preparation
seoaration
distilation

Question 14

alkene -> alkane

Answer 14

H2
Ni catalyst

Question 15

alkene -> haloalkane

Answer 15

hydrogen halide

Question 16

alkane to haloalkane

Answer 16

halogen
UV

Question 17

haloalkane -> alcohol

Answer 17

NaOH
reflux

Question 18

alcohol -> haloalkane

Answer 18

NaX
H2SO4

Question 19

alkene-> alcohol

Answer 19

conc H2SO4

Question 20

alkene -> alcohol

Answer 20

H2O(g)/H3PO4
catalyst

Question 21

primary alcohol to COOH

Answer 21

reflux
- K2Cr2O7/H2SO4

Question 22

primary alcohol -> aldehyde

Answer 22

distil
K2Cr2O7/H2SO4

Question 23

secondary alcohol -> ketone

Answer 23

reflux
K2Cr2O7/H2SO4