The most acidic hydrogen atoms are present in:
A.ethane
B.ethene
C.ethyne
D.Benzene
VerifiedHint: We know that the acidic property of a compound can be calculated by the presence of its s-character. Therefore, we must understand that the s-character is the contribution of a sigma type of bond in a process of formation of orbitals called hybridization. Hence, different hybrid orbitals have different percentage of s-character such as: \[sp^3\] have 25% s-character and 75% p-character, \[sp^2\] have 33% s-character and 66% p-character whereas \[sp\] has 50% s-character and 50% p-character. As mentioned above, the more s-character present in a bond, the shorter and stronger is the bond with the most acidic properties. So, a \[sp - sp\] bond is the strongest bond and \[sp^3\] is the weakest bond.
Complete step by step solution:
We can understand that ethyne has the highest percentage of s-character. As the s-character increases, the electronegativity of carbon increases. Hence, carbon attracts strongly bond pair electrons of \[C - H\] bond towards itself, and \[H + \] is quickly set free. Therefore, ethyne acts as an acid. And in the given problem ethyne possesses the most acidic hydrogen atom.
Hybridisation of ${C_2H_2}$
Ethyne is built from hydrogen and carbon atoms. These carbon atoms do not have enough unpaired electrons to form a bond (1 to the hydrogen atom and three to the other carbon atom), so it needs to promote one of the \[2{s^2}\] pair into the empty \[pz\] orbitals during the process.
And, hence option C is the correct answer.
Note: We must understand that the diamond is the hardest substance known on earth due to its tetrahedron structure. In graphite due to the presence of delocalized electrons, it becomes a good conductor of electricity.
