Traite la pentane-2,4-dione par le bromure

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Discussion Overview

The discussion revolves around the treatment of pentane-2,4-dione with isopropyl bromide in a slightly basic anhydrous acetone medium, focusing on the identification of the major isomer (B) obtained from this reaction based on its proton NMR characteristics.

Discussion Character

  • Technical explanation
  • Experimental/applied

Main Points Raised

  • One participant describes the reaction conditions and the yields of the isomers A and B, providing specific NMR data for compound B.
  • Another participant confirms the details of the reaction and the characterization of compound B, seeking to clarify the information presented.
  • A later reply suggests that the methylene group between the two carbonyl groups is fairly acidic and proposes starting with the deprotonated form of pentane-2,4-dione to explore potential products.

Areas of Agreement / Disagreement

Participants generally agree on the reaction conditions and the characterization of compound B, but the identification of B remains unresolved, with differing approaches suggested for further exploration.

Contextual Notes

There may be limitations related to the assumptions about the acidity of the methylene group and the implications for product formation, which are not fully explored in the discussion.

sara901
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on traite la pentane-2,4-dione par le bromure d'isopropyle en milieu faiblement basique dans l'acetone anhydre comme solvant .on obtient deux composés isoméres A et B,avec des rendements respectifs de 28% et de 72%.
Le composé B est caractérisé en R.M.N du proton par :
-un doublet à 1,28ppmd'intensité 6.
-deux singulets d'intensité 3 pour chacun et sortant à 2,02et2,20ppm.
-un heptuplet d'intensité 1 à 4,40ppm.
-un singulet d'intensité 1 à 5,42ppm.
identifier B.
 
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I believe you meant to say...
Treating pentane-2,4-dione with isopropyl bromide in slightly basic anhydrous acetone, two isomers (A and B) are obtained in yields of 28% and 72%. The compound B (the major isomer) is characterized by proton NMR. Examination of the proton NMR spectrum shows a doublet at 1.28ppm (integration gives 6H), a singlet at 2.02 ppm (integration gives 3H), a singlet at 2.20 ppm (integration gives 3H), a heptuplet at 4.40 ppm (integration gives 1H) and a singlet at 5.42ppm (integration gives 1H). What is B?

N'est-ce pas?
 


yes,ecxactly.
 


It will help you to know that the methylene group bewteen the two carbonyl groups is fairly acidic and can be deprotonated. Start with the deprotonated pentane dione and see what products are likely.