In this reaction in a Khan academy video, cyclohexanone reacts with Brady's reagent to form hydrazone product.
My question is why doea Brady's reagent + cyclohexanone not also form an enamine product where the central, secondary amine group attacks the carbonyl?
My two guesses would be sterics and/or electron withdrawing effects of the ring, but is there another reason? Would this product exist, but minimally?
Perhaps the nitrogen next to the aromatic ring could attack the carbonyl group. However:
The bulky phenyl group is closer to the reaction site, and thus causes more steric interference, than would be the case with the primary nitrogen attack.
The nitrogen next to the phenyl ring conjugates its electron pair to the ring just as in a typical aromatic amine, so it is electronically deactivated as a nucleophile. This is especially the case when the ring has strongly electron-withdrawing ligands at other position.
Arylhydrazines are thus much more reactive nucleophiles at the nitrogen that is farther from the aromatic ring.
