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Nitrogen compounds

Nitrogen compounds. (Chapter 37). CH 3. NO 2. NO 2. NO 2. Nitrogen containing compound. T.N.T. Proteins Enzymes Drugs. R-N-H R ’. R + R-N-R ” Br - R ’. R-N-R ” R ’. NH 2. Amines. Aliphatic 1 o amine 2 o amine 3 o amine 4 o ammonium cpds Aromatic.

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Nitrogen compounds

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  1. Nitrogen compounds (Chapter 37)

  2. CH3 NO2 NO2 NO2 Nitrogen containing compound • T.N.T. • Proteins • Enzymes • Drugs

  3. R-N-H R’ R + R-N-R” Br- R’ R-N-R” R’ NH2 Amines • Aliphatic • 1o amine • 2o amine • 3o amine • 4o ammonium cpds • Aromatic R-NH2

  4. IUPAC names • CH3NH2 Methanamine • (CH3)2NH N-methylmethanamine • (CH3)3N N,N-dimethylmethanamine • C6H5NH2 Phenylamine (aniline)

  5. Formation of amines • Alkylation of NH3 RX + NH3 R-NH2 + R2-NH + R3N + R4N+X- (NH3 in large excess, 1o amine as main product) • 1o Amine from Amides and Nitriles R-CN  RCH2NH2 (H2/Ni or LiAlH4) RCONH2 RCH2NH2(LiAlH4 /ether than H+)

  6. Formation of Amines • C6H5-NO2 C6H5-NH2 Reducing agent: H2/Ni or HCl,Fe (or Zn, Sn, SnCl2) then OH-

  7. Basicity of Amines

  8. R R H + O H H H N: N H OH- H H Basicity of Amines Order of basicity: 2o > 1o > 3o > NH3 > C6H5NH2 Why?

  9. R + H N H H Explanation • Solvation of protonated amine in water by hydrogen bonding (more H, better solvation) • NH3>1o>2o>3o H2O H2O H2O

  10. R R N: R + R R H N R Explanation • Effect of the inductive electron push of the R groups • Increase the basicity • Stabilize the alkylammonium ion • 3o>2o>1o>NH3

  11. .. NH2 ..- + NH2 Explanation • Lone pair e- partly incorporated into benzene ring • Less ready for protonation

  12. NaOH NH2 + HCl NH3+ Cl- NH2 + H2O + NaCl Reactions • Salt Formation ?

  13. O O R-NH2 + CH3CCl  CH3CNHR + HCl O O R-NH2 + C6H5CCl  C6H5CNHR + HCl High m.p. Used in identification Reactions • Amide Formation

  14. RNH2 + NaNO2 + HCl  [RN+N]Cl- Aliphatic Diazonium salt (unstable) ROH H2O -H+ R+ + N2 C=C (evolution of N2 serves as a test for 1o amine) X- R-X Reaction with Nitrous acid • HNO2 prepared by NaNO2 + HCl • 1o aliphatic amines

  15. N+N Cl- NH2 + NaNO2 + HCl  Reaction with Nitrous acid • 1o aromatic amine (stable at temp.<5oC, greater stability by dispersing charge into the benzene ring)

  16. .. .. .. O N+ N+ O O N H2O+ N O HO N O .. .. + N O Ar Ar NH2 NH2 Mechanism -H2O H+ -H+ + H+ .. .. + Ar NH N O Ar N N OH Ar N N OH2 .. -H2O + + Ar N N: Ar N N:

  17. + N: N Stability of Ar-N+N

  18. Benzenediazonium salt • C6H5-N2+ Cl- • C-N bond heavily polarized away from benzene ring • C atom accept Nu: (against the norm of aromatic chemistry) • Has considerable synthetic value

  19. CuCl ArCl CuBr ArBr CuCN Ar-N2+ + N2 ArCN I- ArI H2O ArOH Benzenediazonium salt • Can be replaced by a variety of function groups • High yield • No multiple substitution

  20. .. OH O- N=N+: 1 + NaOH (Napthalen-2-ol) Ice cold 1 N+= N- HO Coupling reaction Orange II, Azo dye (1876) Also serve as a test for 1o aromatic amine

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