Question

Give the hybridization of each atom (except \(\mathrm{H}\) ) in the solvent dimethylsulfoxide. (Unshared electron pairs are not shown.)

Short answer

Answer: The hybridization of each carbon atom in DMSO is sp^3, and the hybridization of the sulfur atom is sp^2.

Step-by-step solution

Find the Steric Number of each Atom

To find the hybridization of each atom, we first need to find the steric number. The steric number is the number of bonding and non-bonding electron pairs surrounding an atom. It is calculated by adding the number of sigma bonds, pi bonds, and lone (non-bonding) electron pairs around the atom. For carbon atoms in DMSO: Each carbon atom has 4 sigma bonds, with 3 bonds to hydrogen atoms and one bond to either a sulfur or oxygen atom. Therefore, the steric number for the carbon atoms is 4. For the sulfur atom in DMSO: The sulfur atom forms 2 sigma bonds (one to the carbon atom and one to the oxygen atom) and has 1 lone electron pair (even though it's not shown in the exercise). The pi bond to the oxygen does not count towards the steric number, only sigma bonds and lone pairs are considered. Therefore, the steric number for the sulfur atom is 3.

Determine the Electron Domains

To determine the hybridization, we need to consider the electron domains around each atom. The electron domains are equal to the steric number. For each carbon atom, there are 4 electron domains, and for the sulfur atom, there are 3 electron domains.

Identify the Hybridization

Using the steric number and electron domains, we can identify the hybridization of each atom in the molecule. For carbon atoms with 4 electron domains: hybridization = sp^3 For the sulfur atom with 3 electron domains: hybridization = sp^2 In conclusion, the hybridization of each carbon atom in the DMSO molecule is sp^3, and the hybridization of the sulfur atom is sp^2.

Key concepts

Understanding Steric Number

In the world of chemistry, the steric number provides essential insight into the shape and reactivity of molecules. At its core, the steric number represents the number of electron clouds, including both bond pairs and lone pairs, around a central atom. To calculate the steric number, you need to add together the number of single bonds (also known as sigma bonds) to the atom, and the number of lone pairs it possesses.

For atoms in organic compounds like dimethylsulfoxide (DMSO), we usually observe steric numbers that range from two to six. This number directly correlates with the atom's hybridization. For instance, a steric number of four suggests an sp^3 hybridization, which we see in the carbon atoms of DMSO as they are connected by four single bonds to other atoms with no lone pairs.

Understanding the steric number is crucial because it allows us to anticipate both the bonding nature and spatial arrangement of atoms within a molecule, paving the way for understanding more complex chemical behavior.

Sigma Bonds and Pi Bonds

Psi

Electron Domains and Their Role

When it comes to electron domains, think of them as individual territories occupied by electrons. They could be either bond domains, where two atoms share electron pairs to form bonds, or lone pairs, where electrons are localized on a single atom.

In every molecule, the distribution of electron domains determines its overall shape, as per the VSEPR theory (Valence Shell Electron Pair Repulsion). Essentially, electron domains want to be as far apart as possible to minimize repulsion. Hence, the number of these domains around a central atom can predict the molecule's geometry.

For example, in the case of DMSO, we identify the electron domains to find the hybridization states of carbon and sulfur atoms. Carbon, with four sigma bonds, has four electron domains leading to a tetrahedral shape introduced by sp^3 hybridization. Sulfur, having two sigma bonds and one lone pair, has three electron domains, signifying a trigonal planar shape indicative of sp^2 hybridization. Recognizing these domains is integral to understanding how molecules will interact and react with one another, which is especially relevant in organic solvents like DMSO that are widely used in chemical processes.