Question

Number the following compounds in order of increasing pKa value.

Short answer

The pKa is used to indicate the acidic strength.We can define pKa as a negative log of Ka, as Ka is an acid dissociation constant. Lower the value of pKa, stronger is the acid, while on the other hand,if the pKa value is high it indicates that the acid is weak.

Step-by-step solution

Step-by-Step SolutionStep 1: pKa

The pKa is used to indicate the acidic strength.We can define pKa as a negative log of Ka, as Ka is an acid dissociation constant. Lower the value of pKa, stronger is the acid, while on the other hand,if the pKa value is high it indicates that the acid is weak.

Increasing order of pKa values of the compounds

Stronger acid has a lower pKa value. In the above compounds, hydrogen which is present between the two carbonyl groups is the most acidic and has the lowest pKa value. In the second compound, oxygen next to the carbonyl group decreases the acidic strength, and hence, it is less acidic than the first one.

Increasing order of pKa