Amines

10.1-2 Amines

  • Amines are organic compounds derived from ammonia (NH3) by replacing one or more hydrogen atoms with alkyl or aryl groups.

    • Primary Amines (1°): Amines where one hydrogen atom of ammonia is replaced (R-NH2).

    • Secondary Amines (2°): Amines where two hydrogen atoms of ammonia are replaced (R2-NH).

    • Tertiary Amines (3°): Amines where three hydrogen atoms of ammonia are replaced (R3-N).

    • The classification of amines (primary, secondary, tertiary) is based on the number of carbon-containing groups bonded to the nitrogen atom.

10.1-2 Amines (continued)

  • Naming of Amines:

    • Simple amines are named as alkylamines, considering the number of alkyl groups present:

    • Diaryl or Trialkylamines: Amines with two or three alkyl groups respectively.

    • Examples:

    • Hexylamine: C6H13-NH2

    • Isobutylamine: C4H11-NH2

    • Methylpropylamine: C4H11-NH

    • Dimethylpropylamine: C5H13-N

10.3-5 Main Properties of Amines

  • Acid/Base Equilibrium in Water:

    • Amines act as weak bases in aqueous solution.

    • They contain a lone pair of electrons which can be utilized to accept a proton (H+), resulting in the formation of ammonium ions (RNH3+).

10.3-5 Main Properties of Amines (continued)

  • Protonation of Amines:

    • Upon protonation, amines exhibit significantly enhanced solubility in water due to the ionization effect.

10.6 Synthesis of ArNH2

  • Method for Synthesis:

    • Reduction of nitro groups on phenyl rings can yield aromatic amines (ArNH2).

10.7 Common Nucleophiles

  • Definition of a Nucleophile:

    • A nucleophile is a molecule or ion possessing a relatively high-energy electron pair (typically from lone pairs or π-electrons).

10.7 Amines as Nucleophiles

  • Reactivity of Amines:

    • Amines can act as nucleophiles in chemical reactions.

    • The reactions involving amines can be complex due to competing side reactions.

    • Importance of understanding amines as better nucleophiles compared to RNH2 (the reasons for this comparison should be elaborated upon in future studies).

Strategy to Avoid Over-Alkylation

  • To mitigate over-alkylation in reactions involving amines, the following strategy is suggested:

    • Use large excess of the amine (e.g., CH3NH2 or NH3) when reacting with alkyl halides (e.g., Br, CI) to limit the number of substitutions occurring on the nitrogen.

    • Avoid the production of unwanted quaternary ammonium salts (e.g., NHCH3).