Organic I - reactions with nitrogen nucleophiles

What is the overall reaction with a nitrogen nucleophile?

• Occurs by addition followed by elimination

• Reaction can be acid catalysed (gives C=O protonation) but depends on the nucleophile - optimum pH for each reaction is dependent on R group identity

• Forms an intermediate iminium ion

• Can remove water to favour product formation

What is the overall hydrolysis reaction with nitrogen nucleophiles?

Uses a H+ catalyst and excess water - eg dilute acid

How can nitrogen-containing compounds form imines?

• Uses an amine and carbonyl

• H+ catalyst is used for aromatic amines

• Most stable if aldehyde/ketone has an aromatic substituent that is stabilised through conjugation (Schiff bases) - delocalisation of electrons lowers energy and increases stability (further stabilised if an aromatic amine is used)

How can imines be hydrolysed?

• Most easily hydrolysed if the R group is an alkyl or H

• Aldehydes and NH3 will hydrolyse very easily

How can nitrogen nucleophiles form oximes?

• Nitrogen nucleophile contains an OH group (hydroxyl amine)

• Reaction is very pH sensitive - acidic conditions deactivate the nucleophile

• Reaction is carried out under neutral or basic conditions

What is the oxime functional group?

R2—C=N-OH

How can hydrazones be formed from nitrogen nucleophiles?

• React the carbonyl with H2N-NH2

• Forms a hydrazone and water

• Highly crystalline compound with sharp melting points - used to characterise aldehydes and ketones

What is the hydrazone functional group?

R2—C=N-NH2

What does reacting a carbonyl with a secondary amine form?

Enamines