SolutionsNitronate and related anions
Exercise 1
Write the product of the Henry reaction between nitromethane and benzaldehyde, and the products of its dehydration and of its reduction with H2/Pd.
Henry: 2-nitro-1-phenylethanol, PhCH(OH)CH2NO2. Dehydration: (E)-β-nitrostyrene, PhCH=CHNO2. Reduction: 2-amino-1-phenylethanol, PhCH(OH)CH2NH2 (a β-amino alcohol, the skeleton of many adrenergic drugs).
Exercise 2
Why is a nitroalkane much more acidic than a ketone? On which atom does the charge of the nitronate mainly reside?
The nitro group is a very strong electron-withdrawing group, both inductively (the nitrogen bears a positive charge) and by resonance: the negative charge is delocalized over the two oxygens. The charge resides mainly on the oxygens (C=N+(O−)2 form), which is why nitronates are easily protonated on oxygen (aci form).