Luminol and synthesis (mechanism of the reaction)

[~christina~]

[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

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

 

[bomba923]

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

 

[~christina~]

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?)

 

[bomba923]

I doubt it,
though it is possible for some statistically minute quantity of 3-nitrophthalic acid to react exactly as such

 

[~christina~]

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? until it reacted that is.

 

[bomba923]

Most likely :)

 

[~christina~]

Most likely :)

Thank you for your assistance with my question.