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Luminol and synthesis (mechanism of the reaction)

  • #1
~christina~
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[SOLVED] Luminol and synthesis (mechanism of the reaction)

In lab I synthesized luminol and I'm trying to figure out the mechanism of the reaction.

3-nitrophthalic acid + hydrazine => 5-nitrophthalhydrazide + Na2SO4=> Luminol

http://spot.pcc.edu/~gbackes/ORGANIC/CH%20243/Synthesis.of.Luminol.htm [Broken]

I know that the reaction is a condensation reaction in the first step but I am not sure how the reaction happens. (do the 2 sides of the molecule attack the hydrazine and then water falls off or does something else happen?)

I looked up the reaction online but the mechanism is not shown. The just say "condensation reaction" and I do notice that the water is missing and the 2 molecules end up joined but as to

who attacks who and then how does the water leave??

Thanks
 
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Answers and Replies

  • #2
759
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Roughly put,
1) Lone pair on hydrazine attacks carboxylic carbon
2) Proton transfers from hydrazine to carboxylic -OH
3) Condensation: one water molecule (i.e., protonated hydroxyl) removed (& formation of amide bond)
4) Repeat steps 1-3 for the other carboxylic acid group, with the remaining -NH2 group on hydrazine
 
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  • #3
~christina~
Gold Member
715
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Roughly put,
1) Lone pair on hydrazine attacks carboxylic carbon
2) Proton transfers from hydrazine to carboxylic -OH
3) Condensation: one water molecule (i.e., protonated hydroxyl) removed (& formation of amide bond)
4) Repeat steps 1-3 for the other carboxylic acid group, with the remaining -NH2 group on hydrazine
Does the reaction happen with both sides at the same time? (both N's of the hydrazine?)
 
  • #4
759
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I doubt it,
though it is possible for some statistically minute quantity of 3-nitrophthalic acid to react exactly as such
 
  • #5
~christina~
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I doubt it,
though it is possible for some statistically minute quantity of 3-nitrophthalic acid to react exactly as such
Oh, so would that other nitrogen just hang there then? untill it reacted that is.
 
  • #6
759
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Most likely :)
 
  • #7
~christina~
Gold Member
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Most likely :)
Thank you for your assistance with my question. :smile:
 

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