Organic synthesis Flashcards
(45 cards)
Which reactions increase chain length?
- KCN with a halogenoalkane to produce a nitrile
- HCN with an aldehyde or ketone to produce a hydroxynitrile
- Friedel-Crafts alkylation to introduce a side chain to a benzene ring
What reactions decrease chain length?
- Soda lime with an acid or its salt to produce an alkane
- Iodoform with a methyl ketone to produce a carboxylic acid salt
What does miscible mean?
Liquids are completely soluble in each other at all concentrations.
How do you separate miscible liquids which do not decompose at or below their boiling temperature?
Distillation can be used to separate the product from the reaction mixture.
What is another use of distillation other than separating miscible liquids?
It is used to separate a volatile liquid from other substances in the mixture that are not volatile.
When is fractional distillation used?
When separating miscible liquids with boiling temperatures closer together.
How do you separate miscible liquids which decompose before or at their boiling temperature?
Distillation is carried out under reduced pressures or steam distillation is used, allowing the compounds to boil at lower temperatures.
How do you separate immiscible liquids?
Steam distillation is used, where steam is passed into the reaction mixture and the volatile compounds pass over with steam and condense in the receiving flask.
When is solvent extraction used?
When a compound has differing solubility in two immiscible solvents. Two different layers of a mixture can be separated using a separating funnel.
How do you separate insoluble solids?
Filtration is used to separate the solid from the liquid present. This can be carried out using a filter paper and a funnel. Once the solid is in the funnel it needs to be washed with an appropriate solvent and dried in the air or a drying oven.
Why is the use of fluted filter paper quicker than normal filter paper?
As the filtrate only needs to travel through one layer of filter paper and the paper only touches the funnel at the folds.
How do you separate soluble solids from solution?
The products are obtained by crystallisation.
What do you need to do if the solution obtained from crystallisation is coloured?
The solution is boiled with decolourising charcoal, and filtered hot to remove the charcoal that contains the absorbed colour.
What are the steps for recrystallisation when the solute is impure?
- Dissolve the solute in a minimum volume of hot solvent
- Filter hot, if necessary, to remove insoluble impurities
- Allow to cool
- Filter
- Wash the solid with a small amount of ice cold solvent
- Dry at a temperature below its melting temperature
What is polymerisation?
The joining together of a large number of monomer molecules.
What types of molecules undergo addition polymerisation?
Alkenes, where the C=C bond is lost.
What is condensation polymerisation?
A large number of monomer molecules joining together with the loss of small molecules.
How can you recognise addition polymerisation?
If the monomer is an alkene
If no small molecules is lost and the polymer is the only product
If the chain only consists of carbon atoms
How can you recognise condensation polymerisation?
If the monomers contain -NH2, -COOH or -OH
If the chain contains an amide or ester linkage
What is PET?
A polyester made from ethane-1,2-diol and benzene-1,4-dicarboxylic acid.
What are the properties of PET?
It is a good insulator so is made into synthetic fibres, but does not easily biodegrade.
What is Nylon 6,6?
A polyamide made from two monomers with six carbon atoms.
What is Kevlar?
A polyamide made from benzene-1,4-dioic acid and benzene-1,4-diamine.
What are the properties of Kevlar?
It is fire retardant and is five times stronger than steel, so it is used in bulletproof vests.
