Amines and their Derivatives | Organic Chemistry 3
Naming the Amines
Amines = derivatives of ammonia NH3, in which one, two or three of the H have been replaced by alkyl or aryl groups.
The -ane ending of the corresponding alkane is replace by -anamine. Same rules as alcohols.
For secondary and tertiary amines:
- largest alkyl group = main chain
- other alkyl groups = substituents named by using the letter N-
Amine function has the lowest order of precedence of all functional groups (except alkene and alkyne).
We use prefixe amino- when the amine is a substituent.
Properties of Amines
Alkanamine is tetrahedral
Properties similar to alcohols and ethers.
- serve as nucleophile
- participate in hydrogen bonding (high boiling point + soluble in water)
- be both basic and acidic
Oxygen is more electronegative than Nitrogen
⇒ Amines are less acidic than alcohols
⇒ Amines are more basic and nucleophilic than alcohols and ethers
⇒ Amines have weaker hydrogen bonding than alcohols
NMR: 1H broad signal and variable δ (1.0-2.5 ppm)
IR: N-H stretching ⇒ broad band ~ 3250-3500 cm-1
Preparation of Amines
Amines by alkylation:
Step 1: Nucleophilic Substitution
Step 2: Deprotonation
And then, subsequent alkylation.
Amines from azides:
Amines by reductive amination:
Step 1: Condensation
Step 2: Reduction
Amines from carboxylic amides:
Amines from nitriles:
Mannich reaction can be considered a variation of the aldol condensation:
Step 1: Iminium ion formation
Step 2: Carbon-carbon bond formation
Step 3: Deprotonation