Reactions · Henry 1895
Henry reaction (nitroaldol addition)
Overview
RCH₂NO₂ + R'CHO → R'CH(OH)CH(NO₂)R
Base-catalysed addition of a nitroalkane to an aldehyde or ketone to give a β-nitro alcohol. Key C-C bond-forming step in the Knoevenagel-Henry route to β-nitrostyrenes (e.g. P2NP).
Conditions: Glacial acetic acid (or 80 % aq. AcOH for milder conditions); primary amine catalyst (n-butylamine, 5-20 mol%). Run at 20-25 deg C in the dark for the slow variant, or at reflux (~118 deg C glacial) for the faster Knoevenagel variant. Workup: pour onto cold water, filter the yellow nitroalkene, recrystallise from MeOH or EtOH.
- Expected yield
- 60–75 %
- Expected duration
- 5-14 days at RT in the dark; 3-6 h at reflux (Knoevenagel variant)