Question

Draw a three-dimensional representation of the oxygen-bearing carbon atom in ethanol, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\), using the standard convention of solid, wedged, and dashed lines.

Short answer

The carbon is sp3 hybridized, using solid, wedged, and dashed lines for tetrahedral geometry.

Step-by-step solution

Identify the functional group

In ethanol, \( ext{CH}_{3} ext{CH}_{2} ext{OH}\), the functional group is alcohol (OH). The oxygen-bearing carbon atom is bonded to both the OH group and the ethyl group (CH2).

Determine the hybridization

The carbon in question is sp3 hybridized because it forms single bonds with four atoms: two hydrogens, one carbon, and one oxygen.

Visualize the geometry

The sp3 hybridization indicates a tetrahedral geometry, where bond angles are approximately 109.5 degrees. This implies that the bonds are directed towards the corners of a tetrahedron.

Assign bond representations

For the three-dimensional representation: Use a solid line for the bond in the plane of the page, a wedged line for a bond coming out of the page, and a dashed line for a bond going behind the page.

Draw the structure

Place the oxygen-bearing carbon in the center. Represent the carbon-hydrogen bond (in the plane) with a solid line. Use a wedged line for the bond connecting to the OH group, which appears to come out towards the viewer. Use a dashed line for the bond to another hydrogen, going away from the viewer. The bond to the ethyl group remains in the plane with a solid line.

Key concepts

Functional Group Identification

In chemistry, identifying the functional group of a compound is one of the primary steps to understanding its properties and reactivity. A functional group is a specific group of atoms within a molecule that is responsible for a characteristic of that compound. In ethanol,

• The functional group is the hydroxyl group (-OH), which characterizes alcohols.
• The -OH group in ethanol is bonded to a carbon atom, giving rise to its classification as an alcohol.

Recognizing that ethanol contains an -OH group helps us understand its potential interactions, such as hydrogen bonding with water molecules, making it soluble in water. This functional group largely influences the chemical behavior and reactivity of ethanol. By identifying it, students can predict how it might behave in different chemical reactions.

sp3 Hybridization

Hybridization is a vital concept that allows us to understand how atomic orbitals mix to form new, hybrid orbitals. These hybrid orbitals dictate the geometry and bonding properties of molecules. In ethanol, the oxygen-bearing carbon atom demonstrates **sp3 hybridization**. Here’s why:

• When a carbon atom forms single bonds (sigma bonds) with four other atoms, it utilizes one s-orbital and three p-orbitals. These orbitals combine to form four equivalent sp3 hybrid orbitals.
• The oxygen-bearing carbon in ethanol binds to two hydrogen atoms, one oxygen atom, and one carbon atom from the ethyl group, all through single bonds.

This understanding is crucial because it helps predict the molecule's three-dimensional shape and potential for bond rotation and reaction with other compounds.

Tetrahedral Geometry

The three-dimensional structure of a molecule is often defined by its geometrical shapes. In ethanol, the sp3 hybridization of the oxygen-bearing carbon leads to a **tetrahedral geometry**:

• The bonds are oriented towards the corners of a tetrahedron, which means the bond angles are approximately 109.5 degrees.
• This configuration maximizes the distance between the bonded electron pairs, minimizing repulsion according to VSEPR theory (Valence Shell Electron Pair Repulsion theory).

Understanding tetrahedral geometry is essential for visualizing molecular shapes, estimating relative distances between atoms, and interpreting stereochemical properties. This geometrical arrangement is fundamental to organic chemistry, affecting physical and chemical properties of molecules like ethanol.