Problem 127 - A Complete Resource Book in Chemistry for JEE Main

Question

Select the incorrect statement about Buckyball or Buckminister fullerene? (a) It is an allotrope of carbon. (b) It is referred as C-60 and C-70. (c) In it carbon atoms are sp \(^{3}\) hybridised. (d) It is inert like diamond.

Step-by-Step Solution

Answer

Statement (c) is incorrect: Carbon atoms in buckyballs are sp \(^2\) hybridized, not sp \(^3\).

Step 1: Identify the Definition

A buckyball is a type of fullerene and is a spherical arrangement of carbon atoms. Fullerenes are an allotrope of carbon, much like diamond and graphite. Therefore, statement (a) is correct.

Step 2: Understand the Structure

Buckyballs are most commonly referred to as C-60 (containing 60 carbon atoms) and less commonly as C-70 (containing 70 carbon atoms). So, statement (b) is also correct.

Step 3: Examine Hybridization

In buckyballs, the carbon atoms are actually sp \(^2\) hybridized, not sp \(^3\) as in statement (c). This incorrect hybridization statement makes (c) potentially the wrong choice.

Step 4: Analyze Chemical Properties

Buckyballs are not inert like diamond. They are more reactive due to their structure, which creates strain and makes them more likely to participate in chemical reactions. Thus, statement (d) is also incorrect.

Key Concepts

Carbon Allotropes

Carbon is a versatile element and exists in different forms, known as allotropes. Each carbon allotrope has unique physical and chemical properties connected to how carbon atoms are bonded.
Examples of carbon allotropes include:

• Diamond: In this allotrope, each carbon atom is tetrahedrally coordinated to four other carbons through sp³ hybridization, forming a rigid three-dimensional lattice that contributes to its hardness.
• Graphite: Here, carbon atoms are arranged in flat, two-dimensional sheets with layers held together by van der Waals forces. The atoms within a layer are bonded through sp² hybridization, allowing electrons to move freely and giving graphite its electrical conductivity.
• Fullerenes: This is a family of carbon allotropes consisting of carbon atoms linked in closed hollow structures. Buckminsterfullerene, or C₆₀, is a prominent example, resembling a soccer ball with hexagon and pentagon patterns.

Fullerenes, also called buckyballs, are distinct due to their unique closed-cage structure, differing significantly from the more common linear or planar configurations found in other carbon allotropes.

Hybridization in Buckminsterfullerene

Hybridization involves the mixing of atomic orbitals to form hybrid orbitals that are suitable for bonding. In the case of Buckminsterfullerene, the key is understanding the type of hybridization that occurs among its carbon atoms.
The carbon atoms in Buckminsterfullerene adopt an sp² hybridization. This means:

• Each carbon atom uses one s orbital and two p orbitals to form three sp² hybrid orbitals.
• The remaining p orbital overlaps with neighboring p orbitals to form \(\) bonds, creating the distinctive double bonds found within the structure.

As a result, the structure of C₆₀ contains both single and double bonds, similar to those seen in aromatic compounds. This sp² hybridization contributes to its stability, while also providing flexibility for the molecule to undergo various chemical reactions. Unlike sp³ hybridization found in diamonds, sp² hybridization offers planar connections, linking every carbon atom to three others.

Chemical Reactivity of Fullerenes

Fullerenes, including the well-known C₆₀ Buckminsterfullerene, possess unique chemical reactivity. Despite being a carbon allotrope like the inert diamond, fullerenes are much more reactive.
Several aspects contribute to this increased reactivity:

• Curved Structure: Unlike the flat sheets of graphite or the rigid structure of diamond, the spherical shape of fullerenes introduces strain in the carbon-carbon bonds. This strain can promote openness to chemical reactions, allowing fullerenes to undergo various transformations.
• Unsaturated Bonds: The sp² hybridization creates \(\) bonds that are more reactive compared to the  bonds in sp³ hybridized carbon.
• Electron Mobility: The overlap of p orbitals allows fullerenes to participate in electron-transfer reactions, making them suitable candidates for both biological and materials science applications.

Because of these properties, fullerenes can readily engage in addition reactions, where other atoms or groups attach to the carbon framework, expanding their utility in fields like drug delivery, electronics, and nanotechnology.