Q.Secondary nitroalkanes react with nitrous acid to form a

A primary or secondary nitroalkane's alpha-hydrogen is acidic because the strongly electron-withdrawing -NO2 group stabilises the conjugate base (the aci-nitro anion) once that hydrogen is removed -- so much so that nitroalkanes are MORE acidic than aldehydes, ketones, esters or cyanides bearing a comparable alpha-H, and dissolve in aqueous NaOH to form a genuine salt. Acidity FALLS as more alkyl groups are attached to the alpha-carbon, since each alkyl group's electron-donating (+I) effect works against -NO2's electron-withdrawing pull: the measured order is nitromethane (CH3-NO2) > nitroethane (CH3CH2-NO2) > 2-nitropropane ((CH3)2CH-NO2), acidity falling steadily as +I donation …