Random - 29-3-2011 at 04:50
I want to attempt hoffman degradation of benzamide to aniline on small scale, can I use just bleach or I need to add sodium hydroxide to bleach? Maybe
I can substitut sodium hydroxide with carbonate or bicarbonate?
bbartlog - 29-3-2011 at 08:05
Bleach often has some NaOH in it already to keep it safely basic (or I suppose it might be there as a result of decomposition of the bleach; I
actually don't know; but it's in there).
Anyway, even without looking up pkA values for various amide substrates, I would say that sodium carbonate (let alone bicarbonate... that's barely
even basic...) is not going to be able to deprotonate your amide in order to get the reaction to proceed.
I also notice that bromine is normally used instead of chlorine. The wikipedia page on the Hofmann degradation / rearrangement (http://en.wikipedia.org/wiki/Hofmann_degradation) has two references that are review papers of the reaction; I think you should get your hands on
those and see what they tell you about possible variations in the reaction.
Random - 29-3-2011 at 10:01
Well, I don't have bromine or even currently NaOH, do you think there will be enough NaOH in bleach to complete hoffman degradation? Some NaOH is
generated in the first step of hoffman degradation as it chlorinates the amide. But there is 2nd step which also uses NaOH to hydrolyze the
isocyanate. If there won't be enough NaOH, I could poison myself with isocyanate which will stay there in the solution.