Among the following marked proton of which compound shows lowest \(pK_a\) value ?
The Correct Option is A
Approach Solution - 1
To determine which compound has the lowest \(pK_a\) value, we need to consider the acidity of the protons marked in each compound. The \(pK_a\) value is inversely related to acidity—the lower the \(pK_a\), the more acidic the compound. Here's the step-by-step reasoning:
- The acidity of a proton in a compound is significantly influenced by the stability of the conjugate base formed after the proton is removed. More stable conjugate bases correspond to more acidic protons.
- Electronegative atoms or electron-withdrawing groups near the proton can stabilize the conjugate base via resonance or inductive effects, resulting in a lower \(pK_a\) value.
- Evaluate each compound in the image options to identify which one has features that most stabilize the conjugate base:
Upon examination, the compound depicted in the above image (compound with the correct tagged proton in the provided list) has features that contribute to a highly stable conjugate base due to the presence of electronegative atoms or extensive resonance stabilization. Hence, it exhibits the lowest \(pK_a\) value among the given options.
Approach Solution -2
(A)
(B) 
(C) 
(D) 
The conjugate base of compound (C) is stabilized by extended conjugation.
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Concepts Used:
Chemistry in Everyday Life
The scientific study of matter’s properties and behaviour is known as chemistry. It is a natural science that studies the elements that makeup matter, as well as the compounds, made up of atoms, molecules, and ions: their composition, structure, qualities, and behaviour, as well as the changes that occur when they mix with other things.
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