hjhearle - 13-11-2012 at 12:16
Tried making up a solution of Brady's reagent as part of derivative formation with cinnamaldehyde today.... trouble is it looked like lumpy bright red
poster paint. Horrible gloop! 
Sure this isn't right! It didn't exactly
precipitate how I expected...
Is there any specific ratio in which to add the conc. suplhuric acid, methanol and 2,4-dnp?
Magpie - 13-11-2012 at 13:26
See Vogel, p. 1061, in the forum library.
Although not specifically identified as Brady's reagent, it says:
"Suspend 2.0 of 2:4 dinitrophenylhydrazine in 100mL of methanol; add cautiously and slowly 4.0 mL of con sulfuric acid. The mixture becomes
warm and the solid usually dissolves completely. Filter if necessary."
I presume that's 2.0g of 2,4 DNPH.
unionised - 13-11-2012 at 14:16
Some DNPH derivatives are rather insoluble and don't form nice crystals when synthesised.
The aromatic aldehyde derivatives are (generally) orange or red so there's a good chance you have the right stuff.
Of course, it's possible that you have just got DNPH back, but if the red stuff formed as a ppt then some sort of reaction presumably took place.
(btw I have spent quite a lot of time playing with DNPH derivatives- I might remember to look for a picture sometime.
hjhearle - 13-11-2012 at 14:31
thanks for this, yeah would be good to see some photos make sure i'm doin the right thing 
cheers
chemrox - 13-11-2012 at 23:59
Maybe you went too fast .. do you have enough to try again? Post a photo or two..
hjhearle - 27-11-2012 at 05:28
Yeah I expect so.... didn't notice the "add cautiously" bit the first time.... oops Could have turned nasty....
The solution did grow fairly warm and there was a ppt (take it that means precipitate?- I'm fairly new to this!) but it wasn't exactly clearly
defined.
Unfortunately, whilst I have some of the "ingredients" left, I don't have the time to try again, having just left school to work for my local
council... and I'd just been granted access to a local university laboratory too!
Sorry guys, looks like this is the end of the line for me! however, it is still a piece of private interest.
Other thing is, does anyone know the definitive melting point of a (2E)-3-Phenylacrylaldehyde-2,4-dinitrophenylhydrazone? Records for various sources
are not concurrent...
hjhearle - 27-11-2012 at 05:29
Just realised that could have been abbreviated to cinnamaldehyde-2,4-DNP. A bit shorter! lol