Home
Class 12
CHEMISTRY
Amines are less reactive in substitution...

Amines are less reactive in substitution reactions. Their reactivity is much lesser than alcohols and alkylflourides towards substitution. Protonation of the amino group makes it a better leaving group, but not nearly as good a leaving group as a protonated alcohol. Protonated amino groups cannot be displaced by `OH^(-)` because it would react immediately with the acidic hydrogen which would convert it in to a poor nucleophile.
The leaving group in quartenary ammonium ion has about the same leaving tendency as a protonated amino group but does not have acidic hydrogen. The reaction of a quartenary ammonium ion with hydroxide ion is known as Hoffmann elimination reaction. The leaving group is tertiary amine. Since a tertiary amine is only a moderately good leaving group, the reaction requires heat. The carbon to which the tertiary amine is attached is designated as `alpha` carbon.
When the hydroxide ion starts to remove a `beta` H from a quartenary ammonium ion, the leaving group does not immediately start to leave because a tertiary amine is not a good leaving group. As a result, a partial negative charge builds up on the carbon from which the proton is removed.
Which of the following statements is correct?

Promotional Banner

Topper's Solved these Questions

  • ALDEHYDES AND KETONES

    AAKASH SERIES|Exercise Problem|36 Videos
  • ALDEHYDES AND KETONES

    AAKASH SERIES|Exercise Exercise-3.1.1|5 Videos
  • ALDEHYDES AND KETONES

    AAKASH SERIES|Exercise Conversions (Structure of products, Starting materials or reagents)|17 Videos
  • ALCOHOLS, PHENOLS AND ETHERS

    AAKASH SERIES|Exercise ETHERS (OBJECTIVE EXERCISE-4)|50 Videos
  • ALKYL AND ARYL HALIDES

    AAKASH SERIES|Exercise OBJECTIVE EXERCISE - 4 (ASSERTION (A) & REASON (R) TYPE QUESTIONS)|19 Videos

Similar Questions

Explore conceptually related problems

Amines are less reactive in substitution reactions. Their reactivity is much lesser than alcohols and alkylflourides towards substitution. Protonation of the amino group makes it a better leaving group, but not nearly as good a leaving group as a protonated alcohol. Protonated amino groups cannot be displaced by OH^(-) because it would react immediately with the acidic hydrogen which would convert it in to a poor nucleophile. The leaving group in quartenary ammonium ion has about the same leaving tendency as a protonated amino group but does not have acidic hydrogen. The reaction of a quartenary ammonium ion with hydroxide ion is known as Hoffmann elimination reaction. The leaving group is tertiary amine. Since a tertiary amine is only a moderately good leaving group, the reaction requires heat. The carbon to which the tertiary amine is attached is designated as alpha carbon. When the hydroxide ion starts to remove a beta H from a quartenary ammonium ion, the leaving group does not immediately start to leave because a tertiary amine is not a good leaving group. As a result, a partial negative charge builds up on the carbon from which the proton is removed. Which of the following statements are true regarding Hoffmann elimination ?

Amines are less reactive in substitution reactions. Their reactivity is much lesser than alcohols and alkylflourides towards substitution. Protonation of the amino group makes it a better leaving group, but not nearly as good a leaving group as a protonated alcohol. Protonated amino groups cannot be displaced by OH^(-) because it would react immediately with the acidic hydrogen which would convert it in to a poor nucleophile. The leaving group in quartenary ammonium ion has about the same leaving tendency as a protonated amino group but does not have acidic hydrogen. The reaction of a quartenary ammonium ion with hydroxide ion is known as Hoffmann elimination reaction. The leaving group is tertiary amine. Since a tertiary amine is only a moderately good leaving group, the reaction requires heat. The carbon to which the tertiary amine is attached is designated as alpha carbon. When the hydroxide ion starts to remove a beta H from a quartenary ammonium ion, the leaving group does not immediately start to leave because a tertiary amine is not a good leaving group. As a result, a partial negative charge builds up on the carbon from which the proton is removed. The compounds 'C' in question number 31 on heating with moist silver oxide gives

In L-Phenyl alanine the amino group lies at

In benzyl amine amino group is a

Primary amino group is absent in

Primary amino group is absent in

Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides due to

AAKASH SERIES-ALDEHYDES AND KETONES-Conversions (Name Reaction and reagents :)
  1. Explain Clemenson's reduction and Wolf Kishmer reduction reactions.

    Text Solution

    |

  2. The reagent used in the Wolff-Kishner reduction is

    Text Solution

    |

  3. Which of the following is an example of aldol condensation react...

    Text Solution

    |

  4. Describe the Cross aldol condensation .

    Text Solution

    |

  5. Cannizzaro reaction involves

    Text Solution

    |

  6. Silver mirror test with Tollen's reagent is given by

    Text Solution

    |

  7. Which of the followig reagents are used to distinguish aldehydes from ...

    Text Solution

    |

  8. Benedict's solution is not reduced by

    Text Solution

    |

  9. The reagents which don't react with glucose are I) Schiff's reagent II...

    Text Solution

    |

  10. Sodium hypochlorite is used in

    Text Solution

    |

  11. Explain the Aldol term. Give an example of the reaction .

    Text Solution

    |

  12. Which of the following represent an acetal/ ketal

    Text Solution

    |

  13. Explain the Hemiacetal term. Give an example of the reaction .

    Text Solution

    |

  14. Amines are less reactive in substitution reactions. Their reactivity i...

    Text Solution

    |

  15. Schiff's bases are formed when aniline reacts with

    Text Solution

    |

  16. Cyanohydrin formation constant will be highest for ?

    Text Solution

    |

  17. Explain the Oxime term. Give an example of the reaction .

    Text Solution

    |

  18. Which of the following reagents can form a hydrazone with alkanone?

    Text Solution

    |

  19. Draw the structures of the 2,4-dinitrophenylhydrazone of benzaldehyde ...

    Text Solution

    |

  20. Explain the Semicarbazone term. Give an example of the reaction .

    Text Solution

    |