Question

The bond between carbon atom (1) and carbon atom (2) in compound \(\mathrm{N} \equiv \mathrm{C}-\mathrm{CH}=\mathrm{CH}_{2}\) involves the hybridization (a) \(\mathrm{sp}^{2}\) and \(\mathrm{sp}^{2}\) (b) \(\mathrm{sp}^{3}\) and sp (c) sp and sp \(^{2}\) (d) sp and sp

Short answer

The bond hybridization is (c) sp and sp^{2}.

Step-by-step solution

Identify Carbon Hybridization in Acetylene-like Bond

Looking at the bond, \(\mathrm{N}\equiv\mathrm{C}-\), the bond between carbon atom (1) and carbon atom (2) is identical to a typical acetylene group (\(\equiv\)). Carbons involved in triple bonds typically use \(sp\) hybridization due to the need for two \(p\) orbitals to form two pi bonds and one \(sp\) hybrid orbital to form a sigma bond.

Examine the Second Carbon's Additional Bond

Carbon atom (2) is involved in a double bond with a hydrogen (\(\mathrm{CH}=\mathrm{CH}_{2}\)). To accommodate a pi bond and two sigma bonds, this carbon must use \(sp^{2}\) hybridization, supporting the three bonds (one double bond and one single bond) with three \(sp^{2}\) hybrid orbitals and one unhybridized \(p\) orbital.

Confirm the Hybridization Pair

Based on the hybridization details, carbon atom (1) uses \(sp\) hybridization for the triple bond, whereas carbon atom (2) uses \(sp^{2}\) hybridization for its role in the \(C=C\) double bond. Thus, the hybridization pair for the bond between these two carbon atoms is \(sp\) and \(sp^{2}\).

Key concepts

Acetylene group bond structure

Acetylene, one of the simplest alkyne compounds, has a unique bond structure within its group. It features a carbon-carbon triple bond, characterized by the linear geometry of the atoms involved. This configuration occurs as each carbon atom in the acetylene group is connected by one sigma bond and two pi bonds. To achieve this bonding, each carbon in acetylene undergoes sp hybridization.

In more detail, sp hybridization occurs when one s orbital combines with one p orbital, forming two hybrid orbitals oriented 180 degrees apart. This allows for the formation of the linear structure typical of triple bonds. The remaining two p orbitals in each carbon remain unhybridized and are perpendicular to each other. They overlap side-by-side to form the two pi bonds, completing the triple bond structure.

Such bonding leads to a rigid and linear acetylene group, which is essential for maintaining the stability and reactivity unique to alkynes. The strength and rigidity derived from the triple bond have significant implications for the compound's properties, such as its high energetic characteristics.

Carbon-carbon triple bonds

Carbon-carbon triple bonds are a defining feature of alkynes and are made up of one sigma bond and two pi bonds. The strength of a carbon-carbon triple bond is significant due to the combination of all three bond types, making it one of the strongest bonds in organic chemistry.

The sigma bond in a triple bond is created through the overlap of sp hybrid orbitals from each carbon atom. This overlap occurs along the line connecting the carbon atoms, providing the bond's main axis of symmetry and strength.

Meanwhile, each of the two pi bonds forms from the side-to-side overlap of unhybridized p orbitals present on each carbon. These p orbitals are oriented perpendicularly to each other, and to the sigma bond, adding to the bond's overall stability and complexity.

These characteristics of carbon-carbon triple bonds confer a high degree of rigidity and a linear structure to molecules containing them. This configuration can influence not just physical properties, but also the reactivity of compounds in which these bonds are present, contributing to their usefulness in synthetic chemistry.

Sigma and pi bonds

In organic chemistry, understanding sigma and pi bonds is crucial for deciphering molecular structures and behaviors. Sigma (σ) bonds are the primary bonds between atoms. They form through the end-to-end overlap of atomic orbitals, such as sp hybrid orbitals. Sigma bonds are characterized by their strong bond strength and axial symmetry along the line connecting the nuclei. This orientation allows for free rotation of the bonded atoms around the bond axis, though this property is restricted in multiple bonded systems like double or triple bonds.

On the other hand, pi (π) bonds form due to the side-to-side overlap of unhybridized p orbitals above and below the plane of the atoms involved. Pi bonds add additional linkages between atoms beyond the initial sigma bond. They contribute to the structure's rigidity and fix the orientation of the atoms, preventing rotation around the axis of the pi bond.

In a triple bonded system, like the one found in the acetylene group, each pi bond supplements the strength and restrictiveness of the main sigma bond. Together, they provide a framework that defines the molecule's structural geometry and chemical behavior, offering a pathway to understand the reactivity and application of complex organic molecules.