Rank the bold-faced hydrogens for the following compounds from most acidic to least acidic.
A)IV II III V I
B)II IV I V III
C)IV I III II V
D)I IV II V III
E)I IV II III V

Question

Rank the bold-faced hydrogens for the following compounds from most acidic to least acidic. 
A)IV > II > III > V > I 
B)II > IV > I > V > III 
C)IV > I > III > II > V 
D)I > IV > II > V > III 
E)I > IV > II > III > V

Quizplus · Accepted Answer

The acidity of a hydrogen is determined by the stability of the resulting anion upon deprotonation. The more stable the anion, the more acidic the hydrogen. In compound I, the resulting anion is stabilized by resonance with the adjacent carbonyl group. In compound IV, the resulting anion is stabilized by resonance with the adjacent benzene ring. In compound II, the resulting anion is stabilized by resonance with the adjacent carbonyl group and by inductive effects from the adjacent fluorine atoms. In compound III, the resulting anion is stabilized by resonance with the adjacent carbonyl group, but is destabilized by the adjacent electron-withdrawing nitro group. In compound V, the resulting anion is not significantly stabilized by any nearby functional group. Therefore, the order of acidity is I > IV > II > III > V, and the best choice is E.

Rank the Bold-Faced Hydrogens for the Following Compounds from Most