PRPM112 LAB: EX 12

• AMINES


  organic compounds composed of an amino group (–NH2 )
• AMINES


  are derivatives of ammonia in which one or more of the hydrogens has been replaced by an alkyl or aryl group
• AMINES


  these group of compounds are classified as primary, secondary or tertiary amines depending on the number of alkyl or aryl group directly bonded to the nitrogen atom
• SYNTHESIS OF AMINES

  • are commonly prepared through reduction reactions of nitro, nitrites and amino compounds
  • first form a carbon-nitrogen bond by reacting a nitrogen nucleophile with a carbon electrophile
  • extraneous nitrogen substituents that may have facilitated this bonding are removed, thereby producing the amine product
• primary amines


  are usually prepared by direct alkylation of ammonia by alkyl halides
• REACTIONS OF AMINES

  1. REACTION WITH CONCENTRATED HCl
  2. REACTION WITH BROMINE WATER
  3. HINSBERG’S TEST
  4. REACTION WITH NITROUS ACID
• REACTION WITH CONC HCl

  aniline

  formation of solid product; formation of smoke
• most amines are Brønsted-Lewis bases,
• REACTION WITH BROMINE WATER

  aniline

  clear colorless solution with white precipitate
• amines may also react with bromine water, producing a decolorized solution with white precipitate
• reaction is the same with phenol, however the product formed results to 2,4,6-tribromophenylamine which appears as white precipitate with a side product of hydrobromic acid which results to decoloration of the solution
• REACTION WITH BROMINE WATER

  the reaction involved is an electrophilic aromatic substitution
• HINSBERG’S TEST

  aniline

  1. formation of precipitate

  N-methyl aniline

  1. formation of precipitate

  N,N-dimethyl aniline

  1. clear colorless solution
• HINSBERG’S TEST


  • function of test: used to differentiate primary, secondary and tertiary amines
  • reagent: benzene sulfonyl chloride
  • positive results: sulfonamides from primary amines are soluble in water and re-precipitating with dilute HCl while those from secondary amines are insoluble in water and dilute HCl
• primary and secondary amines react with benzene sulfonyl chloride to give solid sulfonamide derivatives whereas, tertiary amines do not give any product other than the starting amine; this test is conducted in aqueous base (NaOH, KOH) and the benzene sulfonyl chloride reagent appears as an insoluble oil
• REACTION WITH NITROUS ACID

  aniline

  1. formation of effervescence

  1% glycine

  1. formation of effervescence
• REACTION WITH NITROUS ACID


  • function of test: used to differentiate primary, secondary and tertiary amines
  • reagent: nitrous acid
  • positive results:
  • primary amine – formation of effervescence;
  • secondary amine – yellow, oily layer;
  • tertiary amine – clear colorless solution
• 1. primary amines react with nitrous acid forming nitrogen gas with an alcohol as products;
  2. secondary amines react with nitrous acid producing N-nitrosamine;
  3. tertiary amines react with nitrous acid producing water-soluble ammonium salts
• REACTIONS OF NITRO COMPOUNDS

  1. FERROUS HYDROXIDE TEST
  2. JANOVSKY’S TEST
• NITRO


  • group of organic chemicals usually composed of benzene and its homologues with an attached nitro group (–NO2 )
  • nitrobenzene, picric acid (trinitrophenol) and TNT (trinitrotoluene)
• NITRO


  the nitrogen of this compound has a formal positive charge, which is a strong electrophile
• FERROUS HYDROXIDE TEST

  nitrobenzene

  1. reddish brown precipitate
• FERROUS HYDROXIDE TEST


  function of test: used to identify nitro compounds

  reagent: ferrous ammonium sulfate, sulfuric acid and alcoholic KOH solution

  positive result: reddish brown precipitate
• nitro compounds oxidize ferrous hydroxide forming a reddish-brown precipitate of ferric hydroxide, while the nitro compound is reduced to a primary amine
• FERROUS HYDROXIDE


  reaction involved:

  R–NO2 + 6 Fe(OH)2 + 4 H2O → R–NH2 + 6 Fe(OH)3
• JANOVSKY’S TEST

  • nitrobenzene

  1. light yellow solution

  • picric acid

  1. blood red solution

  • 2,4-dinitrobenzene

  1. bluish-purple solution
• during the late 19th century, Janovsky discovered that when nitro compounds are treated with acetone in an alkaline environment, these compounds will yield colored complexes due to the formation of Meisenheimer complexes
• • mono-nitro substituted benzene will give light yellow solution,
  • di-nitro substituted benzene will give a bluish-purple solution
  • tri-nitro-substituted benzene will give a blood red solutio
• REACTIONS OF AMINO ACIDS AND PEPTIDES

  1. NINHYDRIN TEST
  2. BIURET TEST
• AMINO ACIDS AND PEPTIDES


  • building blocks of macromolecules proteins
  • the structure of an amino acid is composed of a carboxyl group, an amino group, and substituent groups all attached to an α-carbon
• these amino acids form polymers through a nucleophilic attack to the carbonyl carbon of the carboxyl group of one amino acid by the amino group of another amino acid
• this reaction forms an amide bond in between the two linked amino acids; the resulting structure is known as a peptide
• NINHYDRIN TEST


  • 1% glycine

  1. blue solution

  • aniline

  1. golden brown solution
• NINHYDRIN TEST


  • function of test: general test for the presence of amino acids
  • reagent: ninhydrin (yellow solution, is a very strong oxidizing agent)
  • positive result: blue to purple solution
• ninhydrin reacts with the amino acid producing an intermediate product hydrindantin, which further reacts forming Ruhemann’s complex
• Amino acid proline 


  produces a bright yellow color
• asparagine 


  yields a brown-colored product
• BIURET TEST

  • urea

  1. purple or pink solution

  • 1% albumin

  1. purple solution

  • 1% tyrosine

  1. blue solution

  • 1% glycine

  1. blue solution
• BIURET TEST


  • function of test: general test for peptides
  • reagent: cupric sulfate in alkaline solution
  • positive result: purple solution
• biuret (compound produced when urea is heated at 180°C) when treated with dilute cupric sulfate in alkaline condition, a purple-colored product is formed