Question

Which one of the following compounds possesses the most acidic hydrogen?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

-I effect:

1. The substitution has an "I effect," often known as an inductive effect.
2. When the substituent contributes electrons, it produces a +I effect, also known as a positive inductive effect. inductive outcomes.
3. In $\mathrm{C}-\mathrm{F}$ bond, the very electronegative $\mathrm{F}$ atom will pull the $\mathrm{C}-\mathrm{F}$ bond's electrons closer to it.
4. In a region of the molecule where the electron density is higher than elsewhere, an effect is observed around an atom or group that is more electronegative.
5. Alkyl groups, which release (or donate) electrons, are responsible for the -I effect among the less electronegative atoms in the molecule.

The explanation for the correct option:

Option (C):

• Explanation: A hydrogen atom in an acid that dissociates to form a positive ion is known as acidic hydrogen.
• It has a tendency to be released as an ${\mathrm{H}}^{+}$ion.
• Because of the strong $–\mathrm{M}$ impact of the $–\mathrm{CN}$ group, which greatly stabilizes the negative charge.
• It has the most acidic hydrogen among the given compounds. It has the most acidic hydrogen of the given compounds due to the strong$–\mathrm{M}$ effect of the$–\mathrm{CN}$ group, which significantly stabilizes the negative charge.
• Diagram:

The explanation for the incorrect options:

Option (A):

• Explanation: Since the given compound will have less resonance structures, hence it will have stability after loss of ${\mathrm{H}}^{+}$ion.
• The term acidic hydrogen refers to its proclivity to be released as an ion.
• Diagram:

Option (B):

• Explanation: The electron withdrawing effect of this compound doesn't exceed the -M effect of the compound in option (C).
• The stronger the acid, the closer the negative ion is to the ${\mathrm{H}}^{+}$ ion in the molecule.
• Diagram:

Option (D):

• Explanation: The highest percentage of s-character is seen in ethyne, indicating the presence of a more acidic hydrogen atom.
• Since the given compound will have less resonance structures, hence it will have stability after loss of ${\mathrm{H}}^{+}$ion.
• Diagram:

Hence, option (C) is correct.