Question

State the name for each of the following alkanes: (a) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) (c) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) (d) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\)

Short answer

(a) Propane, (b) Pentane, (c) Heptane, (d) Nonane.

Step-by-step solution

Identify the Alkane (a)

For (a) \( \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \), count the total number of carbon atoms in the chain. There are 3 carbon atoms. In alkanes, a chain with three carbon atoms is called **propane**. So, the name of the alkane is propane.

Identify the Alkane (b)

For (b) \( \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \), count the number of carbon atoms. There are 5 carbon atoms in this chain. An alkane with five carbons is known as **pentane**.

Identify the Alkane (c)

For (c) \( \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \), count the carbon atoms in the continuous chain. There are 7 carbon atoms, and alkanes with 7 carbons are named **heptane**.

Identify the Alkane (d)

For (d) \( \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \), count all the carbon atoms in the chain. This molecule has 9 carbon atoms, which corresponds to the alkane **nonane**.

Key concepts

Organic Chemistry

Organic Chemistry is a fascinating branch of chemistry that deals with the study of carbon compounds. Carbon is unique because it can form stable bonds with many elements, including itself. This characteristic makes it incredibly versatile, leading to a vast variety of organic molecules. These compounds are essential in both nature and industry. In nature, organic compounds are crucial for life processes. They make up the molecules found in living organisms, such as proteins, carbohydrates, and fats. In industry, organic chemistry helps create products like plastics, pharmaceuticals, and fuels. One of the foundational concepts in Organic Chemistry is the structure and behavior of hydrocarbons, which include alkanes. Understanding these basic molecules is essential for delving deeper into the more complex structures and reactions in Organic Chemistry.

Naming Alkanes

Naming alkanes is an important part of Organic Chemistry. Alkanes are a type of hydrocarbon, meaning they consist solely of hydrogen and carbon atoms. The naming of these compounds follows a specific set of rules outlined by the IUPAC, ensuring consistency across the globe. To name an alkane:

• First, identify the longest continuous carbon chain. This determines the base name of the alkane and uses a prefix depending on the number of carbon atoms: "meth-" (1 C), "eth-" (2 C), "prop-" (3 C), "but-" (4 C), "pent-" (5 C), "hex-" (6 C), "hept-" (7 C), "oct-" (8 C), "non-" (9 C), "dec-" (10 C), and so on.
• The name ends with "-ane" to signify that the compound is an alkane, which are all saturated hydrocarbons.

For example, as seen in the exercise, a molecule with three carbon atoms is known as "propane." Similarly, a chain consisting of five carbon atoms is named "pentane." Mastering this enables the identification and classification of different hydrocarbons, which is vital for both education and practical application.

Hydrocarbons

Hydrocarbons are the simplest organic compounds, composed entirely of carbon and hydrogen atoms. They are categorized based on the type of carbon-carbon bonds present in their structure. The main classes include alkanes, alkenes, and alkynes. Alkanes are saturated hydrocarbons, meaning all carbon-carbon bonds are single. This saturation gives them stability and less reactivity compared to other types of hydrocarbons. They are also sometimes called paraffins and are commonly found in many everyday products. Some common examples and uses of hydrocarbons include:

• "Methane" (CH₄) which is the primary component of natural gas.
• "Ethane" (C₂H₆) which is used as a petrochemical feedstock.
• "Propane" (C₃H₈) which is widely used as fuel.

Understanding hydrocarbons is essential as they form the backbone of organic chemistry and are integral to many chemical reactions and industrial applications.