Question

The IUPAC name of iso-octane is (A) $2,4,4$-trimethyl pentane (B) $2,2,4$-trimethyl pentane (C) Isopropyl $t$-butyl methane (D) 2,2 -dimethyl-3-ethyl butane

Short answer

The correct IUPAC name for iso-octane is not listed in the given options. However, based on the structure and naming process, the correct IUPAC name should be (E) $2,4,4$-trimethylhexane.

Step-by-step solution

Draw the structure of iso-octane.

First, we need to know the structure of iso-octane. It is a branched hydrocarbon with eight carbon atoms (C8H18) and has the following structure: CH3 | CH3-CH2-CH(CH3)-CH2-CH(CH3)-CH3

Identify the parent chain.

The parent chain is the longest continuous chain of carbon atoms in the molecule. In this case, the parent chain has six carbon atoms as follows: CH3 | CH3-CH(CH3)-CH2-CH(CH3)-CH3 The parent chain forms a hexane molecule.

Number the carbon atoms in the parent chain.

Number the carbons in the parent chain starting from the end closest to the first branch. In this case, we have: 1 -CH3-CH2-CH(3-CH3) -2 -CH(4-CH3)-3 CH3

Identify and number the substituent groups.

The substituents are the carbon groups attached to the parent chain. In this case, there are three methyl groups attached to carbons 2, 4, and 4. We write these as $2,4,4$-trimethyl.

Assemble the IUPAC name.

Combine the substituent groups and parent chain to form the IUPAC name. In this case, the IUPAC name is $2,4,4$-trimethylhexane. Now, let's compare our answer to the provided options: (A) $2,4,4$-trimethylpentane (B) $2,2,4$-trimethylpentane (C) Isopropyl $t$-butylmethane (D) 2,2-dimethyl-3-ethylbutane Comparing the answer $2,4,4$-trimethylhexane to the given options, it can be noticed that option (A) has the closest match, but the parent chain in the option is pentane, whereas in our case it is hexane. Hence, none of the provided options are correct. The correct answer based on our derived IUPAC name should be: (E) $2,4,4$-trimethylhexane

Key concepts

Organic Chemistry

Organic chemistry is the branch of chemistry that focuses on the study of carbon-containing compounds. These compounds may also include elements such as hydrogen, nitrogen, oxygen, and more. This branch of chemistry is fundamental because it touches numerous aspects of science and daily life.
In organic chemistry, the structure, properties, and reactions of organic compounds are explored. This allows scientists to understand how these compounds contribute to different processes and products around us. Carbon's unique ability to form stable bonds with other atoms is what makes organic chemistry so diverse.
Some of the main subfields within organic chemistry include:

• Pharmaceutical Chemistry: Focuses on drug design and production.
• Biochemistry: Discusses the chemistry of living organisms.
• Polymer Chemistry: Deals with large, chain-like molecules called polymers.

Each of these fields uses the core principles of organic chemistry to address specific problems and develop new methods and solutions.

Iso-octane Structure

Iso-octane is a specific arrangement of atoms in a hydrocarbon with the molecular formula C${}_8$H${}_{18}$. Its importance lies in its use as a standard measure in octane rating, which is crucial for understanding fuel quality for engines.
Structurally, iso-octane is a branched hydrocarbon. The unique branching involves two methyl groups attached to the second and fourth carbon atoms of the longest carbon chain. This branching affects the compound's boiling point, melting point, and how it behaves in engines.
The structure of iso-octane is significant because it resists auto-ignition and helps in avoiding engine knocking, an undesirable occurrence in engines. Thus, it is preferred in fuel blends to ensure smooth engine function.
Ultimately, understanding the structure of iso-octane is important in organic chemistry and industrial applications because it exemplifies how slight alterations in structure affect the compound's overall properties.

Nomenclature Rules

Nomenclature in chemistry refers to the systematic naming of chemical compounds based on established rules by IUPAC (International Union of Pure and Applied Chemistry). These rules help in clearly identifying specific compounds without ambiguity.
For naming organic compounds:

• First, identify the longest carbon chain in the structure, which forms the parent name.
• Number the carbon atoms in the chain, starting from the end closest to a branching point.
• Identify and number substituent groups, such as methyl or ethyl, that attach to the main chain.
• Construct the name by combining the position and names of substituents with the parent chain name.

The official IUPAC name should precisely reflect the compound's molecular structure. Therefore, correctly applying these rules is essential for effective communication and understanding in organic chemistry.

Hydrocarbon Naming

Hydrocarbons are compounds made up solely of carbon and hydrogen atoms. They can be classified into different types such as alkanes, alkenes, and alkynes, based on the types of bonds present between carbon atoms. Hydrocarbon naming follows a specific set of guidelines to reflect their structure.
The general steps to name hydrocarbons include:

• Identifying the type of carbon-carbon bonds: single, double, or triple.
• Finding the longest continuous carbon chain, which provides the base name like "hexane," "pentane," etc.
• Noting any variations such as branches or rings, which require additional prefixes and suffixes.

For example, in the hydrocarbon structure for iso-octane, the longest chain is a six-carbon chain, referred to as "hexane," with additional methyl branches. Applying systematic naming rules allows accurate and uniform description across different compounds.
Understanding and using hydrocarbon naming conventions is vital for students and professionals engaged in organic chemistry and related fields.