The carbon-carbon triple bond of an alkyne is composed of:
a. three sigma (o) bonds
b. three pi (10) bonds
c. two sigma (0) bonds and one pi (re) bond
d. one sigma (0) bond and two pi () bonds
e. none of these; write in the correct answer
The correct answer and explanation is :
Correct Answer:
d. one sigma (σ) bond and two pi (π) bonds
Explanation:
Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond (C≡C). This triple bond consists of one sigma (σ) bond and two pi (π) bonds. To understand why, let’s analyze the bonding in alkynes step by step:
- Hybridization of Carbon Atoms in Alkynes
Each carbon involved in a triple bond undergoes sp hybridization. This means:
- The carbon atom uses one s orbital and one p orbital to form two sp hybrid orbitals.
- These sp orbitals form two sigma bonds (one with the other carbon in the triple bond and one with another atom like hydrogen or carbon).
- The remaining two p orbitals (that are not hybridized) remain as pure p orbitals.
- Formation of the Carbon-Carbon Triple Bond
- One sigma (σ) bond forms by the head-on overlap of the two sp orbitals from each carbon.
- Two pi (π) bonds form by the sideways overlap of the two unhybridized p orbitals on each carbon.
- Bonding Summary in Alkynes
- 1 sigma (σ) bond: Strongest, formed by head-on overlap.
- 2 pi (π) bonds: Weaker, formed by sideways overlap.
- Why is This Important?
- The presence of two pi bonds makes the triple bond shorter and stronger than a double or single bond.
- Alkynes show linear geometry (180° bond angles) due to sp hybridization.
- These properties contribute to the high reactivity of alkynes, making them important in organic synthesis.
Here is an illustration of the bonding in an alkyne:
Image Representation of Alkyne Bonding:
Here is the scientific diagram showing the bonding structure of an alkyne. It illustrates the sigma (σ) and pi (π) bonds, sp hybridization, and the linear geometry of the alkyne (ethyne/acetylene, C₂H₂).