[ikakurnia]

i do synthesis schiff base from nitro fenol with dimethylamine benzaldehyde with one pot procedure, it doesnt work. i used Fe/HCl, and ethanol as solvent. then reflux in 65 celcius for 4.5 hours. Base on GC-MS analysis, the result didnt as expected, not form schiff base. anyone know why?
thank you

[Dan]

Look at the general structure of a Schiff base (Wikipedia etc.).

There is a good reason why dimethylamine will not work...

[clarkstill]

I think the idea is to form the aniline in situ by reduction and use that to form the imine? I'm guessing the dimethylamine is there to generate the benzaldehyde-derived iminium species as a better electrophile for reaction with the aniline?

Ikakurnia: if I were you, I'd pre-make/buy the aniline, just to be sure the reduction step is proceeding as planned, or carry it out as a discrete first step. Be careful though - those sort of electron-rich arenes can be pretty bad for you (e.g. the anisidines).  As for forming the schiff base, I've found just stirring the aldehyde and aniline with MgSO4 in toluene is a decent method.

[Dan]

I think the idea is to form the aniline in situ by reduction and use that to form the imine? I'm guessing the dimethylamine is there to generate the benzaldehyde-derived iminium species as a better electrophile for reaction with the aniline?

Ah yes, I didn't read the OP's post properly - my mistake.

Ikakurnia: if I were you, I'd pre-make/buy the aniline, just to be sure the reduction step is proceeding as planned, or carry it out as a discrete first step.

I agree with this completely. I personally prefer catalytic hydrogenation or Zn/CuSO₄ instead of Fe/HCl. I always found Fe/HCl makes a hell of a mess.

[john13579]

Schiff bases are pH sensitive as well with optimal formation around a pH of 5. HCl will hydrolyze any product . For a one pot synthesis you need to adjust the pH after the reduction or use a milder method.