1 / 54

22.15 Nitrosation of Alkylamines

22.15 Nitrosation of Alkylamines. +. H. –. ••. ••. ••. ••. ••. ••. O. O. N. O. N. O. H. • •. • •. • •. ••. ••. +. H. H. H. +. ••. ••. ••. ••. +. O. N. O. O. N. O. • •. • •. • •. • •. • •. +. H. H. Nitrite Ion, Nitrous Acid, and Nitrosyl Cation. ••.

akasma
Download Presentation

22.15 Nitrosation of Alkylamines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 22.15Nitrosation of Alkylamines

  2. + H – •• •• •• •• •• •• O O N O N O H •• •• •• •• •• + H H H + •• •• •• •• + O N O O N O •• •• •• •• •• + H H Nitrite Ion, Nitrous Acid, and Nitrosyl Cation

  3. •• •• N O •• + Nitrosyl Cation and Nitrosation

  4. + •• •• N N O •• •• •• N N O •• •• + Nitrosyl Cation and Nitrosation +

  5. + •• •• •• •• N N N O N O •• •• •• + H + H •• •• + N N O •• •• + H Nitrosation of Secondary Alkylamines • nitrosation of secondary amines gives an N-nitroso amine

  6. •• •• •• N O (CH3)2NH (CH3)2N •• Example NaNO2, HCl •• H2O (88-90%)

  7. N-nitrosodimethylamine(leather tanning) N O (CH3)2N N N N N N O O N-nitrosopyrrolidine(nitrite-cured bacon) N-nitrosonornicotine(tobacco smoke) Some N-Nitroso Amines

  8. R R H + •• •• •• •• N N N O N O •• •• •• + H H + H R H •• •• N N O •• •• + H Nitrosation of Primary Alkylamines • analogous to nitrosation of secondary amines to this point +

  9. R + H •• •• •• •• + N N N O N O •• •• •• H H R R H + H •• •• •• N N N O N O •• •• •• •• + H H + H Nitrosation of Primary Alkylamines R • this species reacts further H

  10. H + + O N N R •• •• •• H R H •• N N O •• •• + H Nitrosation of Primary Alkylamines • nitrosation of a primary alkylamine gives an alkyl diazonium ion • process is called diazotization

  11. + + N N N R R N •• •• •• Alkyl Diazonium Ions • alkyl diazonium ions readily lose N2 to give carbocations +

  12. + HONO N N NH2 – N2 OH H2O + (80%) + (3%) (2%) Example: Nitrosation of 1,1-Dimethylpropylamine

  13. R R R R + •• •• N N N O •• •• R R Nitrosation of Tertiary Alkylamines • There is no useful chemistry associated with the nitrosation of tertiary alkylamines.

  14. 22.16Nitrosation of Arylamines

  15. N(CH2CH3)2 N(CH2CH3)2 1. NaNO2, HCl, H2O, 8°C 2. HO– N O (95%) Nitrosation of Tertiary Arylamines • reaction that occurs is electrophilic aromatic substitution

  16. N O NHCH3 NCH3 (87-93%) Nitrosation of N-Alkylarylamines • similar to secondary alkylamines; • gives N-nitroso amines NaNO2, HCl,H2O, 10°C

  17. + fast + + R N2 RN N + slow + + N ArN Ar N2 Nitrosation of Primary Arylamines • gives aryl diazonium ions • aryl diazonium ions are much more stable thanalkyl diazonium ions • most aryl diazonium ions are stable under the conditions of their formation (0-10°C)

  18. NH2 (CH3)2CH NaNO2, H2SO4 H2O, 0-5°C + N (CH3)2CH N Example: HSO4–

  19. H Ar NO2 Ar NH2 Ar + N N Ar Synthetic Origin of Aryl Diazonium Salts

  20. 22.17Synthetic TransformationsofAryl Diazonium Salts

  21. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  22. + N N Ar OH Ar Preparation of Phenols H2O, heat

  23. NH2 (CH3)2CH OH (CH3)2CH Example 1. NaNO2, H2SO4 H2O, 0-5°C 2. H2O, heat (73%)

  24. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  25. + N N Ar I Ar Preparation of Aryl Iodides • reaction of an aryl diazonium salt with potassium iodide KI

  26. NH2 Br Example I 1. NaNO2, HCl H2O, 0-5°C Br 2. KI, room temp. (72-83%)

  27. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  28. F Ar + N N Ar Preparation of Aryl Fluorides • heat the tetrafluoroborate salt of a diazonium ion; • process is called the Schiemann reaction

  29. NH2 F CCH2CH3 CCH2CH3 O O Example 1. NaNO2, HCl, H2O, 0-5°C 2. HBF4 3. heat (68%)

  30. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  31. Cl Br Ar Ar + N N Ar Preparation of Aryl Chlorides and Bromides • aryl chlorides and aryl bromides are prepared by heating a diazonium salt with copper(I) chloride or bromide • substitutions of diazonium salts that use copper(I) halides are called Sandmeyerreactions

  32. Example NH2 Cl 1. NaNO2, HCl, H2O, 0-5°C 2. CuCl, heat NO2 NO2 (68-71%)

  33. NH2 Cl Example 1. NaNO2, HBr, H2O, 0-10°C Br Cl 2. CuBr, heat (89-95%)

  34. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  35. CN Ar + N N Ar Preparation of Aryl Nitriles • aryl nitriles are prepared by heating a diazonium salt with copper(I) cyanide • this is another type of Sandmeyer reaction

  36. NH2 CH3 Example 1. NaNO2, HCl, H2O, 0°C CN CH3 2. CuCN, heat (64-70%)

  37. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  38. + N N Ar H Ar Transformations of Aryl Diazonium Salts • hypophosphorous acid (H3PO2) reduces diazonium salts; ethanol does the same thing • this is called reductive deamination

  39. NH2 CH3 CH3 Example NaNO2, H2SO4, H3PO2 (70-75%)

  40. Value of Diazonium Salts • 1) allows introduction of substituents such as OH, F, I, and CN on the ring • 2) allows preparation of otherwise difficultly accessible substitution patterns

  41. NH2 NH2 NaNO2, H2SO4,H2O, CH3CH2OH Br Br Br2 H2O Br Br Br (100%) Br (74-77%) Example

  42. 22.18Azo Coupling

  43. + + H N N N N Ar' Ar Ar Ar' an azo compound Ar' must bear a strongly electron-releasing group such as OH, OR, or NR2. Azo Coupling • Diazonium salts are weak electrophiles. • React with strongly activated aromatic compounds by electrophilic aromatic substitution.

  44. OH + N C6H5N OH N NC6H5 Example + Cl–

  45. Section 22.19Spectroscopic Analysis of Amines

  46. H H N N R R H H symmetric antisymmetric Infrared Spectroscopy • the N—H stretching band appears in the range3000-3500 cm-1 • primary amines give two peaks in this region, onefor a symmetrical stretching vibration, the other foran antisymmetrical stretch

  47. RNH2 R2NH Infrared Spectroscopy • primary amines give two N—H stretching peaks, secondary amines give one

  48. H3C H3C CH2NH2 CH2OH  3.9 ppm  4.7 ppm N O C is more shielded than C H H 1H NMR • compare chemical shifts in:

  49.  26.9 ppm  48.0 ppm 13C NMR • Carbons bonded to N are more shielded than those bonded to O. CH3NH2 CH3OH

  50. + NH2 NH3 UV-VIS An amino group on a benzene ring shifts maxto longer wavelength. Protonation of N causesUV spectrum to resemble that of benzene. max204 nm256 nm max230 nm280 nm max203 nm254 nm

More Related