Problem 132 - Introductory Chemistry Atoms First

Question

An organic compound has the formula \(\mathrm{C}_{6} \mathrm{H}_{6}\) and it possesses three \(\mathrm{C}=\mathrm{C}\) double bonds. Draw it.

Step-by-Step Solution

Answer

The organic compound with the formula \(\mathrm{C}_6\mathrm{H}_6\) and three carbon-carbon double bonds is benzene. Its structure can be drawn as: \( \begin{array}{c} \mathrm{H} \phantom{-} \\ | \phantom{-} \\ \mathrm{C}=\mathrm{C} - \mathrm{C} = \mathrm{C} - \mathrm{C} = \mathrm{C} \\[-9pt] | \phantom{-} \\ \mathrm{H} \phantom{-} \end{array} \)

Step 1: Draw a chain of six carbons

Start by drawing a straight chain of six carbon atoms bonded to each other in a line. \( \mathrm{C} - \mathrm{C} - \mathrm{C} - \mathrm{C} - \mathrm{C} - \mathrm{C} \)

Step 2: Add the three carbon-carbon double bonds

To add the three carbon-carbon double bonds, we will convert three of the existing single bonds between adjacent carbons into double bonds. Adding double bonds in an alternating fashion allows for all carbon atoms to participate in double bonding. \( \mathrm{C} = \mathrm{C} - \mathrm{C} = \mathrm{C} - \mathrm{C} = \mathrm{C} \)

Step 3: Attach the hydrogen atoms

To complete the structure of the organic compound, we need to attach the six hydrogen atoms. Each carbon atom should have a total of four bonds (sum of single and double bonds). Here's the final structure: \( \begin{array}{c} \mathrm{H} \phantom{-} \\ | \phantom{-} \\ \mathrm{C}=\mathrm{C} - \mathrm{C} = \mathrm{C} - \mathrm{C} = \mathrm{C} \\[-9pt] | \phantom{-} \\ \mathrm{H} \phantom{-} \end{array} \) Our final result is the structure of benzene, which is an organic compound with the empirical formula \(\mathrm{C}_{6}\mathrm{H}_{6}\) and three carbon-carbon double bonds.

Key Concepts

Organic Chemistry

Organic chemistry is a branch of chemistry focused on the study of organic compounds, which are primarily made of carbon atoms. Carbon's ability to bond with itself and many other elements makes it exceptionally versatile and the backbone of organic chemistry. This versatility results in a vast variety of organic compounds, ranging from simple hydrocarbons to complex biological molecules.
Key features of organic chemistry include:

• The study of carbon-containing molecules and their properties.
• Understanding how atoms are arranged or bonded within a molecule.
• Exploring reactions, synthesis, and behavior of organic compounds.

Benzene, the compound discussed in the exercise, is a fundamental structure in organic chemistry because of its unique stability and specific molecular arrangement. It is a starting point for many chemical reactions, making it an essential concept in this field.

Molecular Structure

Molecular structure refers to the three-dimensional arrangement of atoms within a molecule. It determines the molecule's properties, such as reactivity, polarity, phase of matter, color, magnetism, and biological activity.
In molecules like benzene, the molecular structure is unique because of its hexagonal ring shape, with alternating double bonds that allow electrons to be delocalized across the molecule. This delocalization provides extra stability to the molecular structure, a phenomenon known as aromaticity.
Important aspects of molecular structures:

• The spatial arrangement of atoms.
• The types of bonds between atoms, like single, double, or triple bonds.
• The concept of resonance, especially in stable structures like benzene.

Understanding these structural facets allows chemists to predict how benzene and other similar aromatic compounds will behave in chemical reactions.

Carbon-Carbon Double Bonds

Carbon-carbon double bonds form one of the fundamental building blocks in organic chemistry. They consist of two carbon atoms sharing two pairs of electrons, resulting in a shorter and stronger bond compared to a single bond. This impacts the compound's reactivity and geometry.
In benzene, three carbon-carbon double bonds form in an alternating pattern within its ring structure. These double bonds contribute to benzene's unique chemical stability and resonance, allowing electrons to be shared across all the carbons in the ring rather than being localized between just two carbon atoms.
Key points about carbon-carbon double bonds:

• Double bonds introduce rigidity and restrict the rotation around the bond axis.
• They are involved in reactions like addition and polymerization due to their electron-rich nature.
• In benzene, the double bonds contribute to the delocalized electron cloud, which is characteristic of aromatic compounds.

Recognizing the role of these bonds in benzene is crucial for understanding how the molecule interacts chemically.

Empirical Formula

An empirical formula represents the simplest whole-number ratio of the elements in a compound. Unlike a molecular formula that shows the exact number of each type of atom, the empirical formula provides a reduced snapshot of the compound's elemental composition.
For benzene, the empirical formula is the same as its molecular formula: \(\mathrm{C}_{6}\mathrm{H}_{6}\). This means the ratio of carbon to hydrogen atoms in benzene is 1:1 among the six carbon and six hydrogen atoms.
Important details about empirical formulas:

• They provide a simplified version of the molecule's composition.
• They are useful for identifying unknown compounds and comparing relative compositions.
• In compounds like benzene, empirical and molecular formulas are the same because the molecule's structure does not simplify further.

Understanding the empirical formula is essential for students to grasp the basic make-up of a compound and its most reduced form.