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

Question

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

Quizplus · Accepted Answer

The acidic hydrogen is the one that is most likely to dissociate in water and leave behind a negative charge. In compound I, the hydrogen is attached to a carbon atom that is not next to an electronegative atom, so it is not very acidic. In compound II, the hydrogen is attached to a carbon atom that is next to the carbonyl group, which makes it more acidic. In compound III, the hydrogen is attached to a carbon atom that is next to a nitrogen atom, which makes it more acidic than I but less acidic than II. In compound IV, the hydrogen is attached to a carbon atom that is next to two electronegative oxygen atoms, which makes it the most acidic. In compound V, the hydrogen is attached to a carbon atom that is next to a sulfur atom, which makes it less acidic than III but more acidic than I. Therefore, the correct ranking is II > IV > III > V > I, which is option D.

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