Question

The IUPAC name of neopentane is: (a) 2,2 - dimethylpropane (b) 2-mehylpropane (c) 2,2 - dimethylbutane (d) 2 - methylbytane

Short answer

The IUPAC name of neopentane is 2,2-dimethylpropane.

Step-by-step solution

Identify the Longest Carbon Chain

Examine the structure of neopentane, which is a carbon compound. Neopentane has a total of five carbon atoms bonded together, but these are arranged in such a way that the longest continuous chain you can form is three carbon atoms. There are two remaining carbon atoms, each of which is a "methyl" group, attached to the central carbon of the three-carbon chain.

Locate and Number the Substituents

Since there are two methyl groups attached to the central carbon atom of the three-carbon chain, the central carbon is numbered as position 2. Therefore, these are 2,2-dimethyl groups because both methyl groups are located on the second carbon atom of the main chain.

Formulate the IUPAC Name

Combine the information from Steps 1 and 2 to construct the IUPAC name. The longest carbon chain is a propane chain, and the substituents are both dimethyl groups located on the second carbon. Thus, the correct IUPAC name for neopentane is 2,2-dimethylpropane.

Key concepts

Understanding Organic Chemistry

Organic chemistry is a fundamental branch of chemistry that focuses on the study of carbon-containing compounds. Carbon atoms have the unique ability to form stable covalent bonds with a wide variety of elements, and even with other carbon atoms, making it the backbone of many molecules. This leads to the vast diversity of organic compounds, ranging from simple molecules like methane, to complex structures like proteins and DNA.

A core aspect of organic chemistry is the ability of carbon to form chains of varying lengths and complexities. These chains can have branches, rings, or even be interconnected like a network. Understanding the structure and naming of these compounds is crucial for recognizing their chemical behavior and reactivity. The International Union of Pure and Applied Chemistry (IUPAC) provides a standardized nomenclature to consistently name these diverse structures.

What is Neopentane?

Neopentane, also known as 2,2-dimethylpropane, is a hydrocarbon and an example of an alkane. It belongs to a class of organic compounds that are entirely composed of carbon and hydrogen atoms, linked together in a specific configuration.

Neopentane is an isomer of pentane, meaning it has the same molecular formula \( C_5H_{12} \) as pentane, but a different structural arrangement. In neopentane, four of the carbon atoms are arranged around a central carbon in a "cross"-like shape. The term "neo" indicates a certain level of branching in the structure. This highly branched structure is what gives neopentane its unique properties, such as its lower boiling point compared to other isomers like pentane.

The Process of Carbon Chain Identification

Identifying the longest continuous carbon chain in an organic compound is a crucial step in IUPAC nomenclature. This process lays the foundation for correctly naming the compound.

To determine the longest carbon chain:

• Examine how the carbon atoms are connected in the molecule.
• Locate the maximum number of carbon atoms that form a continuous sequence.
• Ignore any branching groups that deviate from the main sequence during this count.

The main chain dictates the base name of the compound. In the case of neopentane, the longest chain is composed of three carbon atoms, which is known as a "propane" chain in IUPAC terminology. This identification is essential to proceed with other steps, like naming substituents.

Understanding Substituents Naming

Once the main carbon chain is identified, the next step in the IUPAC naming process involves naming the substituents. Substituents are groups of atoms attached to the main chain of the compound. Proper naming and numbering of these groups ensure a consistent and universally understood chemical name.

Substituents are named based on their structure and position:

• Identify the substituent group, like -CH₃ (a methyl group).
• Determine the carbon atom of the main chain to which the substituent is attached. This spot gives the substituent its positional number.
• If there are multiple identical substituents, prefixes like "di-", "tri-" are used, along with their positions, to indicate this in the name.

In neopentane, two methyl groups are located at the same position on the central carbon atom of the longest chain, resulting in the substituent name "2,2-dimethyl". Combining this with the chain name yields the full IUPAC name: 2,2-dimethylpropane.