Question

Which of the indicated hydrogen is most acidic:

A. (x)
B. (y)
C. (z)
D. (p)

Answer 1

Hint: The acidity of the hydrogen depends on various factors. Few of them are the stability of hydrogen and the electronegativity of the atom it is attached to. The stability of the structure can be due to conjugation or inductive effect. We will consider all the parameters for finding the most acidic hydrogen in the compound.

Complete Step By Step Answer:
The acidity of hydrogen depends on some of the factors. Few of them are like the stability of the compound and the electronegativity of the atom to which hydrogen is attached. From the above structure we can observe that the most electronegative atom to which hydrogen is attached is nitrogen. Therefore we can say that we have to find the more acidic hydrogen between p and z.
Now let us assume that (p) hydrogen is removed and then the stability of compound can be observed as:

Therefore the compound will be stabilized by resonance. On the other if a hydrogen (z) is removed then we have the following structure:

Thus it is not stabilized by resonance and hence we can say that the hydrogen (z) will not be acidic more than that of (p).
Thus we can say that the most stabilized structure is obtained when hydrogen (p) is removed thus it is the most acidic hydrogen.
Hence the correct option is D. (p).

Note:
When hydrogen leaves its position then negative charge is developed on the atom on which it is attached. Thus the electronegative element has a higher tendency to gain negative charge. Thus more electronegative atoms having hydrogen will make it acidic. The negative charge will be more stable on electronegative elements than electropositive elements. More the delocalization of electrons more will be the acidity of hydrogen.