General Chemistry 2 Assignment - Preparation of amine (Group 13 and 18)

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General Chemistry 2 Assignment - Preparation of amine (Group 13 and 18)

  1. 1. 1
  2. 2. • organic compounds that contain one or more nitro functional groups: -NO2 (O-N=O) • The O-N=O bond angle is very nearly tetrahedral • There are 2 type of nitro compound: 2 Nitro compound Aromatic Aliphatic zwitter ionic polar structures A positively charged nitrogen and two equivalent negatively charged oxygens
  3. 3. 3 Preparation of amine involves nitration of the ring and subsequent reduction of the nitro group to an amino group –NH2. In aromatic and aliphatic nitro compounds, nitro group undergoes similar reactions. However depending on the attachment of functional groups (aryl or alkyl ), the reactivity may be different.
  4. 4. The various reduction stages of the nitro group are given below: 4 The reaction involve removal of water
  5. 5. • In general, reduction is easily achieved either by catalytic hydrogenation (H2 + catalyst), with reducing metals in acid(Zinc or tin or iron or metal salt such as SnCl2 in dilute mineral acid can also be used) • For example: 5
  6. 6. • As amines can classified to be primary , secondary and tertiary. Most primary amines can be obtained by reduction of nitro compound • The final product depends on the nature of the reducing agent as well as the pH of the medium. 6 CH3CH2NH2 + 2H2O 1。Amine CH3CH2NH2 + 2H2O 1。Amine Catalytic reduction Ni or Pt/3H2 (Given by both aromatic and aliphatic nitro compound) Reduction in acidic medium(6H) Zn/HCl . Fe/HCl.Sn/HCl Zn/NH4Cl(neutral medium) Reducing agent CH3CH2NHOH+H2O N-ethyl hydroxylamine CH3CH2NO2
  7. 7. Aliphatic nitro compounds can be reduced to aliphatic amines using several different : 1) Catalytic hydrogenation using platinum (IV) oxide (PtO2) or Raney nickel 2) Iron metal in refluxing acetic acid 3) Samarium diiodide 7 Aromatic nitro compounds can be reduced to aromatic amines using several different : 1) Zinc Dust and AmmoniumCatalytic 2) Catalytic ydrogenation using platinum (IV) oxide (PtO2) or Raney nickel
  8. 8. Catalytic reduction 8 •The nitro group is easily reduced by catalytic hydrogenation using Pd/C catalyst in ethanol.
  9. 9. Reduction by metal in acidic solutions 9 • Metals (Fe, Sn and Zn) and HCl are sued for reducing a nitro group (-NO2) to an amino group (-NH2).
  10. 10. Reduction with lithium aluminium hydride ,LiAlH 10 • Aliphatic nitro compounds are reduced to p-amines with LiAlH4. Methylnitrobenzene Methylphenylamine
  11. 11. If the reduction involve the nitro compound which have di- and polynitro groups ,hydrogen sulfide in aqueous or alcoholic ammonia is use for selective reduction of one nitro group. Treating 2,4-dinitrotoluene with hydrogen sulfide and ammonia result in reduction of the 4-nitro group. 11 In the reduction of di- or polynitro aromatic compounds by gaseous H2S over a solid catalyst,additions of CO gas promotes the formation of amino group from all nitro groups in the molecule
  12. 12. 12 •The reduction of nitro compound is highly exothermic reaction. The heat is given out when the nitro group is reduce and amino group being form.
  13. 13. 13 In the laboratory, reacting a nitro-aromatic with a mixture of tin and conc. hydrochloric acid by heating under reflux will reduce it to a primary aromatic amine (-NH2 directly attached to benzene ring). In industry , metal like iron powder and acid are used or a direct reduction in the gas phase with hydrogen or transition metal catalyst. C6H5NO2 + 6[H] ==> C6H5NH2 + 2H2O Redox Reaction: 2C6H5NO2(aq) + 14H+ (aq) + 3Sn(s) ==> 2C6H5NH3 + (aq) + 3Sn4+ (aq) + 4H2O(l)
  14. 14. 14
  15. 15. In nitrile reduction, a nitrile is reduced to an amine or with a suitable chemical reagent. Reagents for the conversion to amines are lithium aluminium hydride( LiAlH4), Raney nickel( Nickel catalyst), hydrogen or diborane (B2H6).
  16. 16. This organic reaction is one of several nitrogen- hydrogen bond forming reactions. Reactions are sensitive to acidic or alkaline conditions, which can cause hydrolysis of -CN group.
  17. 17. The reduction of nitriles using LiAlH4 Lithium tetrahydridoaluminate, LiAlH4 is more commonly employed for the reduction of nitriles on the laboratory scale. Similarly, LiAlH4 reduces amides to amines.
  18. 18. There are four hydrogens ("tetrahydido") around the aluminium in a negative ion. The "(III)" shows the oxidation state of the aluminium, and is often left out because aluminium only ever shows the +3 oxidation state in its compounds. The structure of LiAlH4 is:
  19. 19. In the negative ion, one of the bonds is a co-ordinate covalent bond using the lone pair on a hydride ion (H-) to form a bond with an empty orbital on the aluminium. The nitrile reacts with the lithium tetrahydridoaluminate in solution in ethoxyethane followed by treatment of the product of that reaction with a dilute acid.
  20. 20. [H] means "hydrogen from a reducing agent".
  21. 21. The reduction of nitriles using hydrogen and a metal catalyst The carbon-nitrogen triple bond in a nitrile can also be reduced by reaction with hydrogen gas in the presence of a variety of metal catalysts. Commonly quoted catalysts are palladium, platinum or nickel. The reaction will take place at a raised temperature and pressure.
  22. 22. It is impossible to give exact details because it will vary from catalyst to catalyst. For example, ethanenitrile can be reduced to ethylamine by reaction with hydrogen in the presence of a palladium catalyst. Overall, the carbon-nitrogen triple bond is reduced to give a primary amine. Primary amines contain the -NH2 group.
  23. 23. Reduction Of Primary Amides Presenter : See Teck Jia Wong Wei Leong
  24. 24. Amide Reduction  Amides are a group of organic compounds derived from ammonia (NH3).  Amide reduction in chemistry is the organic reduction of amides.  Amides, RCONR'2, can be reduced to the amine, RCH2NR'2 by conversion of the C=O to -CH2-
  25. 25.  Reagents are lithium aluminium hydride and catalytic hydrogenation.  Requires high temperature and pressure.
  26. 26.  The main reaction product is an amine.  The nature of the amine obtained depends on the substituent present on the original amide.
  27. 27. Definition The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one fewer carbon atom.
  28. 28. Mechanism The reaction of bromine with sodium hydroxide forms sodium hypobromite, which transforms the primary amide into an intermediate isocyanate. The intermediate isocyanate is hydrolyzed to a primary amine giving off carbon dioxide
  29. 29. 1) Removal of proton from amide N
  30. 30. 2) Formation of N-Bromo amide
  31. 31. 3) Removal of another proton from amide N
  32. 32. 4) Rearrangement through Migration of aryl group
  33. 33. 5) Hydrolysis of isocyanate intermediate
  34. 34. 6) The formation of amine R―NH2 Amine
  35. 35.  Aliphatic & Aromatic amides are converted into aliphatic & aromatic amines respectively.  In the preparations of Anthranilic Acid from Pthlamide.  Nicotinic acid is converted into 3-Amino pyridine.  The Symmetrical structure of α-phenyl propanamide does not change after hofmann reaction.

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