When compared to the keto form, the enol form of which of the following compounds is most stable?
1
II
III
IV
V
Which compound's? $\mathrm{H}$ is the least acidic?
nitroethane
propanenitrile
propanal
N,N-dimethylacetamide
acetone
Rank the compounds from strongest acids to weakest. To rank items as equivalent, overlap them.