Question

What is the name of each of the following straight-chain alkanes? (a) \(\mathrm{CH}_{3} \mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (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

The names of the given straight-chain alkanes are: (a) Ethane, (b) Octane, (c) Propane, and (d) Nonane.

Step-by-step solution

Identifying the Alkane (a)

The given alkane is \(\mathrm{CH}_{3} \mathrm{CH}_{3}\). This alkane has 2 carbon atoms. According to the IUPAC nomenclature, an alkane with two carbon atoms is called 'Ethane'.

Identifying the Alkane (b)

The given alkane is \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\). This alkane has 8 carbon atoms. In accordance with the IUPAC nomenclature, an alkane with eight carbon atoms is 'Octane'.

Identifying the Alkane (c)

The given alkane is \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\). This alkane has 3 carbon atoms. When using the IUPAC nomenclature, an alkane with three carbon atoms is known as 'Propane'.

Identifying the Alkane (d)

The given alkane is \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\). This alkane has 9 carbon atoms. Therefore, according to the IUPAC nomenclature, an alkane with nine carbon atoms is called 'Nonane'.

Key concepts

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) nomenclature is a systematic method of naming organic chemical compounds as recommended by the IUPAC. Its goal is to ensure that each chemical compound has a unique and unambiguous name, and its use is standard practice in the scientific community. The nomenclature aids in the precise identification of a substance based on its structural formula without requiring additional information.

For naming straight-chain alkanes, the IUPAC system begins with an identification of the longest continuous carbon chain, which determines the base name of the alkane. The number of carbon atoms in the chain gives rise to the prefix (meth- for one carbon, eth- for two, prop- for three, etc.), while the suffix -ane denotes that the hydrocarbon is an alkane, a type of hydrocarbon with single bonds only. For example, an alkane with three carbon atoms would be named propane according to IUPAC nomenclature.

Organic Chemistry

Organic chemistry is a branch of chemistry that focuses on the study of carbon-containing compounds, their properties, synthesis, and reactions. This field encompasses a wide array of substances, including not only compounds with carbon-carbon bonds but also those with carbon-hydrogen bonds. Alkanes, which are the simplest organic compounds consisting solely of hydrogen and carbon atoms connected by single bonds, fall under this category.

Understanding the structure of organic molecules is crucial in organic chemistry. Structural formulas, such as those provided in the exercise, illustrate the specific connections between the atoms in a molecule. Alkanes, due to their simple structure, are often the starting point for learning about organic molecules and serve as a basis for understanding more complex hydrocarbons.

Straight-Chain Alkanes

Straight-chain alkanes are organic compounds that consist of carbon atoms connected in a continuous, linear chain, with hydrogen atoms filling all other bonding sites on the carbon atoms. They don't have any branches or cyclic structures. The general formula for straight-chain alkanes is C_nH_2n+2, where n is the number of carbon atoms.

One of the features of straight-chain alkanes is the predictable progression in their physical properties (such as boiling point, melting point, and density) with increasing chain length. As the molecular weight increases, so do these physical properties, due to the increase in van der Waals forces between molecules.