Question

Give the name of each of the following straight-chain alkanes. a. \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) b. \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) c. \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) d. \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\)

Short answer

a. Octane b. Decane c. Hexane d. Butane

Step-by-step solution

Count the Carbon Atoms - a

Count the carbon atoms in the first molecule: \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\). There are 8 carbon atoms.

Determine the Name - a

The prefix for 8 carbon atoms is "oct-". So, the name of this alkane is octane. b.

Count the Carbon Atoms - b

Count the carbon atoms in the second molecule: \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\). There are 10 carbon atoms.

Determine the Name - b

The prefix for 10 carbon atoms is "dec-". So, the name of this alkane is decane. c.

Count the Carbon Atoms - c

Count the carbon atoms in the third molecule: \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\). There are 6 carbon atoms.

Determine the Name - c

The prefix for 6 carbon atoms is "hex-". So, the name of this alkane is hexane. d.

Count the Carbon Atoms - d

Count the carbon atoms in the fourth molecule: \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\). There are 4 carbon atoms.

Determine the Name - d

The prefix for 4 carbon atoms is "but-". So, the name of this alkane is butane.

Key concepts

Organic Chemistry

Organic chemistry is a fascinating field focusing on the study of carbon-containing compounds, including alkanes. Carbon is unique due to its ability to form stable bonds with other elements and itself. This leads to a diverse range of organic compounds. In organic chemistry, the simplest hydrocarbons are called alkanes, characterized by their single covalent bonds and defined by the general formula \(C_nH_{2n+2}\). This means for every \(n\) carbon atoms, there are \(2n+2\) hydrogen atoms.

Alkanes are the simplest type of hydrocarbon, where each carbon atom is bonded to four other atoms. They have a straightforward structure, making them a good starting point for beginners in organic chemistry. Their simplicity underscores their significance as the fundamental building blocks of more complex organic structures. By studying alkanes and their properties, students gain a grasp of basic organic principles. This knowledge is essential for understanding more complex organic reactions and structures.

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) provides a systematic way to name chemical compounds, ensuring clarity and uniformity across the scientific community. When it comes to naming alkanes, the IUPAC nomenclature is both essential and straightforward. It involves counting the number of carbon atoms present in the longest continuous chain of the molecule.

• The name typically starts with a prefix corresponding to the number of carbon atoms. For instance: 'meth-' for 1, 'eth-' for 2, 'prop-' for 3, 'but-' for 4, and so on.
• The suffix '-ane' is added to denote the presence of only single bonds between carbon atoms, indicating it's an alkane.

For example, for a straight-chain alkane with four carbons (\(C_4H_{10}\)), the name is 'butane.' By learning the IUPAC system, chemistry students can accurately name any alkane no matter how long the carbon chain. This method enhances communication and helps avoid confusion in the expansive field of organic chemistry.

Straight-Chain Hydrocarbons

Straight-chain hydrocarbons, specifically alkanes, are hydrocarbons with a continuous unbranched chain of carbon atoms. They are the simplest form of alkane, making them perfect for introductory discussions around organic chemistry. These chains are structured in linear sequences, without any branches or loops, contributing to their label as 'straight-chain.'

The linear arrangement of straight-chain alkanes contributes to their physical properties, such as boiling and melting points. As the number of carbon atoms in the chain increases, so generally does the boiling and melting point. This happens because larger molecules have greater surface areas, leading to stronger intermolecular forces that require more energy to break.

• For instance, methane (\(CH_4\)), with one carbon, is a gas at room temperature, while decane (\(C_{10}H_{22}\)), with ten carbons, is a liquid.

Understanding straight-chain hydrocarbons gives students a foundational grasp of alkane properties, which can be expanded upon when studying more complex, branched, or cyclic hydrocarbons in organic chemistry.