Nitrogen compounds

Question 1

Define isoelectric point.

Answer 1

The pH value at which there is no overall charge on a particular amino acid in its aqueous solution.

Question 2

Define electrophoresis.

Answer 2

The separation of ions placed in an electric field between a positive and a negative electrode.

Question 3

State the relative basicities of phenylamine, benzylamine and ammonia in aqueous solution. Explain your answer.

Answer 3

Benzylamine > ammonia > phenylamine

Basicity is linked to lone pair on N being able to accept H+.

In benzylamine, alkyl group causes positive inductive effect and increases electron density on N.

In phenylamine, lone pair of N delocalised into pi bonding system.

Question 4

Suggest why Br2 (aq) reacts with C6H5NH2 but not C6H6.

Answer 4

Lone pair of electrons delocalised into the pi bonding system increasing its electron density, which polarise the electrophile better.

Question 5

Explain why benzamide, C6CONH2 is a much weaker base than ammonia.

Answer 5

Lone pair of N is delocalised into C=O group.