Nitrogen Containing Organic Compound

  • Aliphatic Amines
  • Common Names of Aliphatic Amines

Aliphatic Amines

  • Organic compounds containing nitrogen
  • Nitrogen bonded to sp3 hybridized carbon atom(s)
  • Molecules have a lone pair of electrons on the nitrogen atom

Common Names of Aliphatic Amines

  • Primary amines: named by adding suffix “-amine” to the name of the alkyl group attached to the amino group
  • Secondary amines: named by adding suffix “-amine” to the name of the alkyl group attached to the amino group, followed by the name of the alkyl group attached to the nitrogen atom
  • Tertiary amines: named by adding suffix “-amine” to the name of the alkyl group attached to the nitrogen atom, followed by the names of the two alkyl groups attached to the nitrogen atom

Common Names of Aliphatic Amines (Examples)

  • Primary Amine:
    • CH3CH2NH2 (ethanamine or ethylamine)
  • Secondary Amine:
    • CH3CH2NHCH3 (dimethylamine)

Common Names of Aliphatic Amines (Examples)

  • Tertiary Amine:
    • (CH3)3N (trimethylamine)

Comparison of Boiling Points

  • Boiling points of amines are higher than those of analogous alkanes and ethers due to the presence of hydrogen bonding between amine molecules

Solubility of Amines in Water

  • Low molecular weight amines are soluble in water due to the formation of hydrogen bonds between amine and water molecules
  • As the number of carbon atoms increases, solubility in water decreases

Physical Properties of Amines

  • Amines have a distinct odor (fishy smell)
  • Amines are polar compounds
  • Amines can form hydrogen bonds with water

Chemical Properties of Amines

  • Amines are weak bases and can react with acids to form salts
  • Amines can undergo substitution reactions with alkyl halides to form new amines

Chemical Properties of Amines (Equation)

  • Example of a substitution reaction:
    • CH3CH2NH2 + CH3CH2Br -> CH3CH2N(CH3)2Br + HBr
  1. Aliphatic Amines (Structure)
  • Primary amines have the structure R-NH2, where R represents an alkyl group
  • Secondary amines have the structure R-NH-R’, where R and R’ represent alkyl groups
  • Tertiary amines have the structure R3N, where R represents alkyl groups
  1. Preparation of Amines
  • Nucleophilic substitution of halogenalkanes: R-X + NH3/amine -> R-NH2/amine
  • Reductive amination of carbonyl compounds: RCHO/RRCOR’ + NH2-R’’ -> R-CH2-NH2/R’-NH-R''
  1. Reactions of Amines (1)
  • Reaction with acids: R-NH2 + HX -> R-NH3+X-
  • Formation of diazonium salts: R-NH2 + HNO2 + HCl -> R-N2+Cl- + 2H2O
  1. Reactions of Amines (2)
  • Reaction with nitrous acid: R-NH2 + HNO2 -> R-OH + N2 + H2O (for aromatic amines)
  • Reaction with aldehydes/ketones: R2NH + RCHO/RRCOR’ -> R2N-CH=O/R’ (Schiff base)
  1. Preparation of Diazonium Salts
  • Aromatic amines react with nitrous acid (HNO2) to form diazonium salts
  • Diazonium salts are important intermediates in the synthesis of various organic compounds
  1. Reactions of Diazonium Salts (1)
  • Replacement of -N2+ group by other groups: R-N2+X- + Nu- -> R-Nu + X-
  1. Reactions of Diazonium Salts (2)
  • Coupling reactions: R-N2+X- + Ar-NH2 + H+ -> Ar-N2+X- + R-NH3+ (azo dye formation)
  1. Azo Dyes
  • Azo dyes are synthetic dyes that contain one or more azo (-N=N-) groups
  • They have vibrant colors and are widely used in the textile industry
  1. Importance of Amines
  • Amines are important in biological systems, such as neurotransmitters and amino acids
  • Amines are used in the synthesis of pharmaceuticals, dyes, and pesticides
  1. Summary and Key Points
  • Aliphatic amines have the general structure R-NH2, R-NH-R’, or R3N
  • Amines can be prepared by nucleophilic substitution or reductive amination
  • Chemical reactions of amines include reactions with acids, formation of diazonium salts, and coupling reactions

Common Names of Aliphatic Amines (Examples)

  • Primary Amine:

    • CH3CH2NH2 (ethanamine or ethylamine)
    • CH3CH2CH2NH2 (propanamine or propylamine)
    • CH3(CH2)3NH2 (butanamine or butylamine)

  • Secondary Amine:

    • CH3CH2NHCH3 (dimethylamine)
    • CH3CH2CH2NHCH3 (diethylamine)
    • CH3(CH2)3NHCH3 (dipropylamine)

  • Tertiary Amine:

    • (CH3)3N (trimethylamine)
    • (CH3)2CHNHCH3 (dimethylbutylamine)
    • (CH3)(CH2)3N(CH3)2 (ethylpropylamine)

Comparison of Boiling Points

  • Boiling points of amines are higher than those of analogous alkanes and ethers due to the presence of hydrogen bonding between amine molecules
  • The boiling points generally increase with the increase in molecular weight of the amine

Solubility of Amines in Water

  • Low molecular weight amines are soluble in water due to the formation of hydrogen bonds between amine and water molecules
  • As the number of carbon atoms increases, solubility in water decreases
  • Amines with long hydrocarbon chains are insoluble in water but soluble in organic solvents

Physical Properties of Amines

  • Amines have a distinct odor (fishy smell)
  • Amines are polar compounds due to the presence of electronegative nitrogen atom
  • Amines can form hydrogen bonds with water and other polar substances

Chemical Properties of Amines

  • Amines are weak bases and can react with acids to form salts
  • The reaction between an amine and an acid is called acid-base neutralization
  • Amines can undergo substitution reactions with alkyl halides to form new amines or quaternary ammonium salts

Chemical Properties of Amines (Equation)

  • Acid-base neutralization reaction:

    • R-NH2 + HCl -> R-NH3+Cl-
    • R-NH2 + HNO3 -> R-NH3+NO3-

  • Reaction with alkyl halides:

    • R-NH2 + CH3CH2Br -> R-NHCH2CH3 + HBr
    • R-NH2 + (CH3)3CCl -> R-N(CH3)3+Cl-

Preparation of Amines

  • Nucleophilic substitution of halogenalkanes:
    • R-X + NH3/amine -> R-NH2/amine
    • Example: CH3CH2Br + NH3 -> CH3CH2NH2 + HBr
  • Reductive amination of carbonyl compounds:
    • RCHO/RRCOR’ + NH2-R’’ -> R-CH2-NH2/R’-NH-R''
    • Example: CH3CHO + NH2CH3 -> CH3CH2NH2 + H2O

Reactions of Amines (1)

  • Reaction with acids:
    • R-NH2 + HX -> R-NH3+X-
    • Example: C2H5NH2 + HCl -> C2H5NH3+Cl-
  • Formation of diazonium salts:
    • R-NH2 + HNO2 + HCl -> R-N2+Cl- + 2H2O
    • Example: C6H5NH2 + HNO2 + HCl -> C6H5N2+Cl- + 2H2O

Reactions of Amines (2)

  • Reaction with nitrous acid:
    • R-NH2 + HNO2 -> R-OH + N2 + H2O (for aromatic amines)
    • Example: C6H5NH2 + HNO2 -> C6H5OH + N2 + H2O
  • Reaction with aldehydes/ketones:
    • R2NH + RCHO/RRCOR’ -> R2N-CH=O/R’ (Schiff base)
    • Example: (CH3)2NH + CH3CHO -> (CH3)2N-CH=O

Importance of Amines

  • Amines are important in biological systems, such as neurotransmitters and amino acids
  • Amines are used in the synthesis of pharmaceuticals, dyes, and pesticides
  • Amines play a crucial role in the development of synthetic materials and polymers