Question

What type of overlap is involved in the formation of C $-$ H bonds in acetylene molecules?

• A. $sp^3 - s$
• B. $sp^2 - s$
• C. $sp - s$
• D. $sp - sp$

Hint:

Alkanes use $sp^3-s$, alkenes use $sp^2-s$, and alkynes use $sp-s$ for $C-H$ bonds.

Answer 1

The Correct Option is C

To determine the type of overlap involved in the formation of C-H bonds in acetylene molecules, we need to understand the hybridization state of carbon atoms in acetylene (C₂H₂).

1. Acetylene, or C₂H₂, has a linear structure where each carbon atom forms two C-H bonds and one triple bond (C≡C) with another carbon atom.
2. The triple bond comprises one sigma (σ) bond and two pi (π) bonds. For a carbon atom to participate in a triple bond in C≡C, it must be in an \(sp\) hybridized state.
3. In the \(sp\) hybridization, one s orbital mixes with one p orbital (p_x), resulting in two sp hybrid orbitals oriented linearly at 180 degrees apart.
4. The remaining two p orbitals (p_y and p_z) are non-hybridized and are involved in forming the two π bonds of the triple bond.
5. Each carbon in acetylene uses an \(sp\) hybrid orbital to form a sigma bond with the hydrogen's 1s orbital.

Therefore, the overlap involved in the formation of C-H bonds in acetylene is between an \(sp\) hybrid orbital of carbon and an s orbital of hydrogen, which is \(sp - s\).

Conclusion: The correct answer is \(sp - s\), which accurately describes the overlap that occurs during the formation of the C-H bond in acetylene.

Other Options:

• \(sp^3 - s\): This is the overlap in molecules like methane where carbon is \(sp^3\) hybridized.
• \(sp^2 - s\): This occurs in molecules like ethylene where carbon is \(sp^2\) hybridized.
• \(sp - sp\): This describes the overlap involved in the sigma bond formation between the two carbon atoms in acetylene, not with hydrogen.