Question

Draw the structural formula of each of the following. a. ethane \(\quad\) c. propane b. hexane \(\quad\) d. heptane

Short answer

The structural formulas for the given hydrocarbons are: a. Ethane: \(H H\) \(| |\) \(C-C\) \(| |\) \(H H\) b. Hexane: \(H H H H H H\) \(| | | | | |\) \(C-C-C-C-C-C\) \(| | | | | |\) \(H H H H H H\) c. Propane: \(H H H\) \(| | |\) \(C-C-C\) \(| | |\) \(H H H\) d. Heptane: \(H H H H H H H\) \(| | | | | | |\) \(C-C-C-C-C-C-C\) \(| | | | | | |\) \(H H H H H H H\)

Step-by-step solution

Determine the number of carbon atoms for each hydrocarbon

Using the name of each hydrocarbon, which comes from the number of carbon atoms present in the compound, we will know the number of carbon and hydrogen atoms for each structure: a. ethane (2 carbon atoms) b. hexane (6 carbon atoms) c. propane (3 carbon atoms) d. heptane (7 carbon atoms)

Draw the carbon skeleton

In this step, we will connect the carbon atoms with single bonds, creating the backbone of each compound. a. ethane: C - C b. hexane: C - C - C - C - C - C c. propane: C - C - C d. heptane: C - C - C - C - C - C - C

Add hydrogen atoms to each carbon

Now add the hydrogen atoms to each carbon atom, ensuring that every carbon has 4 single bonds. a. Ethane: H H | | C-C | | H H b. Hexane: H H H H H H | | | | | | C-C-C-C-C-C | | | | | | H H H H H H c. Propane: H H H | | | C-C-C | | | H H H d. Heptane: H H H H H H H | | | | | | | C-C-C-C-C-C-C | | | | | | | H H H H H H H

Key concepts

The Essence of Organic Chemistry

Organic chemistry is the scientific study of the structure, properties, and reactions of organic compounds, which are based on carbon. The 'organic' part of the name originally referred to compounds derived from living organisms, but now encompasses all carbon-containing compounds, except for carbon oxides, carbonates, and carbides.

In organic chemistry, hydrocarbons are fundamental as they serve as the foundation for the construction of more complex molecules. Hydrocarbons are compounds comprised solely of carbon (C) and hydrogen (H) atoms. They come in various structures and lengths, and their chemical and physical properties differ as a result. An understanding of hydrocarbons is essential since they are not only used in academic settings but are also prevalent in industries ranging from pharmaceuticals to petrochemicals.

An Introduction to Alkanes

Alkanes are the simplest family of hydrocarbons and are a major subject of study within organic chemistry. Structurally, they are characterized by having single bonds between carbon atoms and a general formula of \( C_nH_{2n+2} \). These saturated hydrocarbons are known for their stability, which makes them less reactive than other types of hydrocarbons like alkenes and alkynes.

Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms, ensuring that each carbon atom forms four single bonds. They are also known as paraffins and can be either straight-chain (normal) alkanes or branched-chain (iso) alkanes. Their names are derived from the Greek word for the number of carbon atoms they contain followed by the '-ane' suffix. For example, 'methane' is a one-carbon alkane, 'ethane' has two carbon atoms, and the pattern continues with 'propane', 'butane', and so on. As the number of carbon atoms increases, so does the number of possible isomers, leading to a rich diversity of alkane compounds.

Molecular Representation in Organic Chemistry

Molecular representation is a critical tool in organic chemistry that allows chemists to visualize and communicate the structure of molecules. Structural formulas, as shown in the problem's solution, represent the atoms of a molecule and the bonds between them. There are different types of molecular representations:

• Lewis structures: These show all the atoms in a molecule, the bonds between them, and any lone pairs of electrons.
• Condensed structures: They offer a simplified version by grouping certain atoms together, commonly used for larger molecules.
• Skeletal formulas (also known as bond-line formulas): These are even more streamlined, showing the carbon skeleton of a molecule with lines representing the bonds. Hydrogen atoms are often omitted for simplicity, as they can generally be inferred.

In the context of textbook solutions like the ones provided, these visual tools enable students to better understand the molecular structure of compounds and thus predict their physical and chemical properties. By practicing with structural formulas, students develop an intuitive sense for the nature of organic molecules that is indispensable for their further studies in the field.