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Luminol and synthesis (mechanism of the reaction)

  1. May 7, 2008 #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 243/Synthesis.of.Luminol.htm

    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
     
    Last edited: May 7, 2008
  2. jcsd
  3. May 7, 2008 #2
    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
     
    Last edited: May 7, 2008
  4. May 7, 2008 #3

    ~christina~

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    Does the reaction happen with both sides at the same time? (both N's of the hydrazine?)
     
  5. May 7, 2008 #4
    I doubt it,
    though it is possible for some statistically minute quantity of 3-nitrophthalic acid to react exactly as such
     
  6. May 8, 2008 #5

    ~christina~

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    Oh, so would that other nitrogen just hang there then? untill it reacted that is.
     
  7. May 8, 2008 #6
    Most likely :)
     
  8. May 8, 2008 #7

    ~christina~

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    Thank you for your assistance with my question. :smile:
     
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