Problem 90
Question
The number and type of bonds between two carbon atoms in \(\mathrm{CaC}_{2}\) are (a) one sigma and one \(\pi\) bond (b) one sigma and two \(\pi\) bonds (c) one sigma and one and a half \(\pi\) bonds (d) one sigma bond
Step-by-Step Solution
Verified Answer
Option (b) one sigma and two \(\pi\) bonds.
1Step 1: Understanding Calcium Carbide
Calcium carbide, CaC2, consists of calcium ions and acetylide ions \(C_2^{2-}\). We need to understand the bonding in the acetylide ion to determine the bonds between two carbon atoms.
2Step 2: Acetylide Ion Structure
The \(C_2^{2-}\) ion involves two carbon atoms that share electrons. The electron configuration can be represented by a triple bond model: a sigma bond and two pi bonds. This triple bond accounts for sharing six electrons, with a strong bond between the two carbons.
3Step 3: Identifying Bonds
In the \(C_2^{2-}\) ion, one sigma bond (\(\sigma\)) forms along the line connecting the two carbon nuclei. In addition, two pi bonds (\(\pi\)) form due to the sideways overlap of p-orbitals, creating a triple bond.
Key Concepts
Carbon-carbon triple bondAcetylide ionSigma and pi bonds in chemistry
Carbon-carbon triple bond
In chemistry, a carbon-carbon triple bond is a strong type of covalent bond where two carbon atoms are connected by three shared pairs of electrons. This bond is characteristic of certain types of molecules, including acetylene and derivatives such as the acetylide ion found in calcium carbide. The triple bond is comprised of one sigma bond and two pi bonds, making it significantly stronger and shorter than a single or a double bond.
The sigma bond in a triple bond is formed by the end-to-end overlap of sp hybrid orbitals from each carbon atom. This forms a direct line of connection between the two nuclei. The pi bonds, on the other hand, are formed by the side-by-side overlap of unhybridized p orbitals.
This unique combination of sigma and pi bonds gives the carbon-carbon triple bond its strength and linear structure. The linearity results from the symmetrical arrangement of the electrons around the carbon atoms, leading to a bond angle of 180 degrees.
The sigma bond in a triple bond is formed by the end-to-end overlap of sp hybrid orbitals from each carbon atom. This forms a direct line of connection between the two nuclei. The pi bonds, on the other hand, are formed by the side-by-side overlap of unhybridized p orbitals.
This unique combination of sigma and pi bonds gives the carbon-carbon triple bond its strength and linear structure. The linearity results from the symmetrical arrangement of the electrons around the carbon atoms, leading to a bond angle of 180 degrees.
Acetylide ion
The acetylide ion, represented as \( C_2^{2-} \), is a negatively charged ion that consists of two carbon atoms sharing electrons through a carbon-carbon triple bond. This ion is part of calcium carbide, \( \text{CaC}_2 \). The negative charge of the acetylide ion results from the extra electrons added to the carbon atoms, allowing it to form a complete octet.
The acetylide ion is highly reactive, especially with metals to form metal acetylides. This reactivity is due to the presence of the carbon-carbon triple bond, which is a region of high electron density. The high electron density makes acetylides excellent nucleophiles, meaning they tend to donate electrons to electrophiles in chemical reactions.
Understanding the structure and reactivity of the acetylide ion helps us appreciate its role in synthesis processes and its involvement in various industrial applications, notably in the production of acetylene gas.
The acetylide ion is highly reactive, especially with metals to form metal acetylides. This reactivity is due to the presence of the carbon-carbon triple bond, which is a region of high electron density. The high electron density makes acetylides excellent nucleophiles, meaning they tend to donate electrons to electrophiles in chemical reactions.
Understanding the structure and reactivity of the acetylide ion helps us appreciate its role in synthesis processes and its involvement in various industrial applications, notably in the production of acetylene gas.
Sigma and pi bonds in chemistry
Sigma and pi bonds are fundamental concepts in chemistry, describing various ways electrons can be shared between atoms. These bonds are not only key to understanding molecular structure but also determine the strength and reactivity of the bonds.
A sigma bond (\(\sigma\)) is the strongest type of covalent bond where two atomic orbitals overlap along a line between the nuclei of two atoms. These bonds allow for free rotation about the bonding axis and are typically formed by the overlap of s and p orbitals. In a carbon-carbon triple bond, one of the bonds is a sigma bond.
Pi bonds (\(\pi\)), on the other hand, are formed by the side-to-side overlap of adjacent p orbitals. Unlike sigma bonds, pi bonds do not allow for rotation due to being aligned perpendicular to the bonding atoms' central axis. Pi bonds add rigidity to molecular structure and, in a carbon-carbon triple bond, they contribute to the bond's overall strength by providing additional electron overlap. These pi interactions are essential in defining the chemical properties and reactivity patterns of molecules.
Understanding sigma and pi bonds is essential for grasping how molecules form, interact, and participate in chemical reactions.
A sigma bond (\(\sigma\)) is the strongest type of covalent bond where two atomic orbitals overlap along a line between the nuclei of two atoms. These bonds allow for free rotation about the bonding axis and are typically formed by the overlap of s and p orbitals. In a carbon-carbon triple bond, one of the bonds is a sigma bond.
Pi bonds (\(\pi\)), on the other hand, are formed by the side-to-side overlap of adjacent p orbitals. Unlike sigma bonds, pi bonds do not allow for rotation due to being aligned perpendicular to the bonding atoms' central axis. Pi bonds add rigidity to molecular structure and, in a carbon-carbon triple bond, they contribute to the bond's overall strength by providing additional electron overlap. These pi interactions are essential in defining the chemical properties and reactivity patterns of molecules.
Understanding sigma and pi bonds is essential for grasping how molecules form, interact, and participate in chemical reactions.
Other exercises in this chapter
Problem 87
An organic compound \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}\) is found to be optically active. Which of the following is correct structure of the given compo
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The number of optical isomers formed by hydrogenation of the compound, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CHCH}_{3}\) are (a) 0 (b) 1 (c) 2 (
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Which of the following has the least hindered rotation about carbon-carbon bond? (a) ethane (b) ethylene (c) acetylene (d) hexachloroethane
View solution Problem 93
The \(\mathrm{Cl}-\mathrm{C}-\mathrm{Cl}\) angle in \(1,1,2,2\)-tetrachloroethene and tetrachloromethane will be about (a) \(120^{\circ}\) and \(109.5^{\circ}\)
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