Problem 34 - A Complete Resource Book in Chemistry for JEE Main

Question

The hybridization of carbon atoms in \(\mathrm{C}-\mathrm{C}\) single bond of \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{CH}=\mathrm{CH}_{2}\) is (a) sp \(^{3}-\mathrm{sp}^{3}\) (b) \(\mathrm{sp}^{2}-\mathrm{sp}^{3}\) (c) \(\mathrm{sp}^{2}-\mathrm{sp}\) (d) \(\mathrm{sp}^{3}-\mathrm{sp}\)

Step-by-Step Solution

Answer

The hybridization of carbon atoms in the single bond is closest to option (c) \( \text{sp}^2 - \text{sp} \).

Step 1: Identify Bonds and Their Types

The molecule given is \( \text{HC} \equiv \text{C}-\text{CH}=\text{CH}_2 \). Look for the \( \text{C}-\text{C} \) single bond in the molecule. This bond occurs between the second and third carbon atoms in \( \equiv \text{C}-\text{CH} \).

Step 2: Determine Hybridization of Each Carbon Atom

The first carbon (\( \text{C} \equiv \)) is part of a triple bond, indicating sp hybridization. The second carbon between the triple bond and the single bond will adopt sp hybridization as it is involved in a bond with two areas of electron density (one triple bond, one single bond). The third carbon atom with \( \text{-CH}= \) is part of a double bond but only involves a single bond with the second carbon, making it sp hybridized as well.

Step 3: Analyze Overall Hybridization for Single Bonds

Since the carbon atoms participating in the single bond are both sp hybridized, the hybridization along the \( \text{C}-\text{C} \) single bond is \( \text{sp-sp} \). However, note that the answer choices provided do not include this option. Instead, evaluate based on the given answers that the sp hybridization matches \( \text{sp}^2-\text{sp} \) as closely as possible, acknowledging that the second bond not involved in the single bond configuration is the \( \text{sp}^2 \) from \( \text{CH}=\text{CH}_2 \).

Step 4: Select the Best Answer from Options

Based on the highest similarity to the given options and understanding step 3's hybridization characteristics, option (c) \( \text{sp}^2 - \text{sp} \) aligns best with the provided answer possibilities, considering double bond presence and sp states.

Key Concepts

Carbon Atoms

The essence of organic chemistry primarily revolves around carbon atoms. These versatile atoms form the backbone of countless molecules, supporting not just simple structures, but also incredibly complex organic compounds. A carbon atom contains four valence electrons, making it adept at forming covalent bonds. Due to this capability, carbon is central to forming chains, rings, and frameworks seen in organic chemistry.

In the context of hybridization, carbon atoms can mix different orbitals to form new hybridized orbitals. This process allows carbon to maintain strong, stable bonds. The common types of hybridization seen in carbon include sp, sp², and sp³. The type determines the molecular geometry and bonding nature of the carbon atom.

Each carbon in a molecule influences the number of sigma (σ) and pi (π) bonds it can form, which in turn affects the molecule's shape and reactivity. Understanding how carbon hybridizes in different situations enhances our ability to predict molecular behavior.

C-C Single Bond

The connection between two carbon atoms via a single bond is fundamental in molecular structures. This type of bond is also referred to as a sigma (σ) bond, characterized by direct overlap of orbitals between the two carbon atoms. It's the result of head-on overlapping of sp hybridized orbitals or other types depending on the geometry of the involved carbons.

In any organic molecule, the C-C single bond provides stability and allows for free rotation around the bond axis. This rotational freedom permits greater flexibility in the molecular geometry, affecting properties like boiling point and solubility.

• In single bonds like these, electrons are shared more evenly, and the bond is quite strong.
• This bond type forms the backbone of alkanes and is an integral part of complex molecules such as polymers.

Understanding the nature of a C-C single bond is crucial as it influences the overall behavior of organic compounds in reactions and interactions.

sp Hybridization

sp hybridization is an important concept in understanding molecule structure and reactivity. This type of hybridization occurs when one s orbital and one p orbital mix, yielding two equivalent sp hybrid orbitals. Typically, carbon atoms involved in forming triple bonds or engaged in linear structures exhibit sp hybridization.

In the molecule given in the exercise, both the carbon atoms that form the C-C single bond are sp hybridized. This form of hybridization is characterized by:

• Linear geometry as the hybridized orbitals arrange themselves at 180-degree angles.
• Capability of forming one sigma and two pi bonds, highly useful in molecules with triple bonds like alkynes.

The concept of sp hybridization also plays a role in understanding the potential for reactivity in organic molecules. Analyzing how these hybrid orbitals interact with other atoms through shared electron pairs can reveal much about the compound's structure-function relationship.