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Question: Rank the following compounds in order of DECREASING acidity. –Free Chegg Question Answer

Rank the following compounds in order of DECREASING acidity.

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The order of decreasing acidity would be:

A > D > B > C

i.e, diketone > diester > ketone > ester

In the given compounds it is the alpha-hydrogen which contributes to the acidity. What is important here is the pka of the (alpha) hydrogens which are adjacent to the respective functional groups. Now, pka = -log (ka) where ka is the acid dissociation constant. Greater the pka, lower will be the ka and hence lower will be the acidity.

The approximate pka’s of the alpha hydrogens are as follows:

– ketone = 20

– ester = 25

– diketone = 9

– diester = 13

Hence, we have : A > D > B > C



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