Chapter 16 Flashcards
Draw a diagram for the process of “ heating under reflux “
…
Why is “ heating under reflux “ used ?
It is a technique used for volatile/flammable reactants/products over a prolonged period of time
Explain the process of “ heating under reflux “
Uses a vertical condenser
This prevents loss of reactants/products as gaseous vapours
Any vapour formed is condensed back to a liquid and returned to the pear shaped flask
Ant bumping granules are required to prevent the mixture from boiling and bumping out of the flask
Draw a diagram for the process of “ distillation “
…
Why is “distillation” used ?
This technique relies on the fact that in a mixture of miscible liquids, each component can be separated due to its unique boiling point
Explain the process of “ distillation “
Bulb of thermometer must be positioned in line with condensor to ensure an accurate reading of the boiling point of each liquid as it is collected
Water supply must be connected and have a continuous water flow around the condensor so water remains cool in order for mixture to be distilled
What apparatus is used to separate immiscible liquids ?
Separating funnel
Describe preparation and purification of an organic liquid including the use of a separating funnel to remove an organic layer from an aqueous layer
1) Pour mixture into separating funnel and some distilled water
2) Add stopper and invert flask to mix the mixture
3) Equalise the pressure by opening the stopper as required
4) Continue shaking until there is no whistle sound
5) To collect water in lower layer, open the stopper and place a beaker under the spout
6) Use another beaker to collect desired organic layer
7) Shake liquid with drying agent
Name 3 drying agents
Magnesium sulphate
Calcium sulphate
Sodium sulphate
all anhydrous
How do you use drying agents ?
Add selected drying agent to organic product
If drying agent forms clumps add some more until they are moving freely - it binds to any water to become hydrated
Use gravity filtration to collect dry product
Filtrate = product
What does re-distillation mean and when is it used ?
It is when a liquid is purified by using multiple distillations
If the product and impurities have similar bp’s a second distillation may be required to obtain a pure product. The narrower the boiling range the purer the product.
Summary to Steps to Prepare an Organic Liquid
1) Heat reaction mixture under reflux ( reaction takes place )
2) Removing aq layer using separating funnel
3) Na2CO3 used to remove acid impurities
4) Removing water using Drying Agent
5) Redistil - pure product
What is the target molecule ?
the compound that the chemist is attempting to make
What is two stage synthesis ?
Identify the functional groups and target molecules
Identify the intermediate that links the starting and target molecules
State the reagents and conditions for each step
Alkane to Haloalkanes : reagents and conditions
Halogen / UV
Alkene to Alkane : reagents and conditions
H2, Ni catalyst
Alkene to Haloalkane : reagents and conditions
Hydrogen Halide
Haloalkane to Alcohol : reagents and conditions
NaOH ( aq )
Heat under reflux
Alcohol to Haloalkane : reagents and conditions
Sodium Halide
H2SO4
Alkene to alcohol : reagents and conditions
H2O (g) / H3PO4 catalyst
Alcohol to alkene : reagents and conditions
Conc H2SO4, heat under reflux
Primary alcohol to aldehyde
distil, acidified dichromate, H2SO4
Primary alcohol to carboxylic acid
heat under reflux, acidified dichromate, H2SO4
Secondary alcohol to ketone
heat under reflux, acidified dichromate, H2SO4
How do alkanes typically react ?
free radical substiution
How do alkenes typically react ?
electrophillic addition
How do alcohols typically react ?
nucleophillic substituition
Dehydration / elimination
How do haloalkanes typically react ?
Nucleophillic substitution
How do ketones / aldehydes typically react ?
Aldehydes will oxidise
How do carboxylic acids typically react ?
Esterification
