4.8 organic synthesis ond analysis

Increases chain length CN

Potassium cyanide with a halogenlalkane

produces a nitrile, which can be hydrolised to produce a carboxylic acid

a nitrilee can be reduced by lithium hydridioaluminate to give an amine

increasing carbon chain- hydrogen cyanide

Addition of a hydrogen cyanide to produce an aldehyde or ketone

followed by the hydrolysis of the hydroxynitrile

In aromatic systems

Friedel crafts/ alkylation reaction is used to introduce a carbon containing side chain to a benzene ring

Decrease in chain length

soda lime

Heating and acid or its salt with soda lime in a decarboxylation reaction

produces an alkane that contains fewer carbon atoms than the starting material

Decreasing carbon chain

triiodomethane/ iodoform

Where a methyl ketone is treated with alkaline iodine

the products are triodomethane and the salt of a carboxylic acid that contains one fewer carbon atom

Flow chart

Separation of miscible liquids

If the product doesn't decompose at or below its boiling temperature and the boiling temperature is not too high then distillation can be used to separate the product from other substances in the reaction mixture

Simple distillation

Can be used if the boiling temperature of the product differs by a reasonable amount from the boiling temperature of the other compound present

can also be used to separate a volatile liquid from other substances in the mixture that's not volatile

Distillation

Eg. 2 chloro 2 methylproane from 2 methylpropan-2-ol and HCl

(CH3)3COH + HCl — (CH3)3CCl + H2O

82 degrees. 51 degrees. 100 degrees

Fractional distillation

Used if the boiling temperature is all closer together

a fraction in column is used which enables a more efficient separation of the products

Miscible

Liquids that are completely soluble in each other at all concentrations

eg. Ethanol and water