Problem 101 - General Chemistry: Principles and Modern Applications

Question

The compound isoheptane is best represented by the formula (a) \(\mathrm{C}_{7} \mathrm{H}_{14} ;\) (b) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{5} \mathrm{CH}_{3}\) (c) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}\left(\mathrm{CH}_{2}\right)_{3} \mathrm{CH}_{3} ;(\mathrm{d}) \mathrm{C}_{6} \mathrm{H}_{11} \mathrm{CH}_{3}\).

Step-by-Step Solution

Answer

The compound isoheptane is best represented by the formula (c) \((CH_{3})_{2}CH(CH_{2})_{3}CH_{3}\)

Step 1: Identify the Right Amount of Carbon and Hydrogen Atoms

In this step, examine each formula and check the number of Carbon and Hydrogen atoms. Isoheptane has 7 Carbon atoms and 16 Hydrogen atoms.

Step 2: Match the Formula with Right Amount of Carbon and Hydrogen Atoms

On comparing the atoms count with the options: (a) \(C_{7}H_{14}\) has 7 Carbon and 14 Hydrogen atoms, (b) \(CH_{3}(CH_{2})_{5}CH_{3}\) has 7 Carbon and 16 Hydrogen atoms, (c) \((CH_{3})_{2}CH(CH_{2})_{3}CH_{3}\) also has 7 Carbon and 16 Hydrogen atoms, and (d) \(C_{6}H_{11}CH_{3}\) has 7 Carbon and 14 Hydrogen atoms. Out of these, options (b) and (c) matches with the atom count of Isoheptane.

Step 3: Match the Iso- Prefix in the Compound’s Name

The prefix iso- in organic chemistry implies that the molecule contains a secondary Carbon atom, which is a Carbon atom connected to two other Carbon atoms. Looking at options (b) and (c), only (c) \((CH_{3})_{2}CH(CH_{2})_{3}CH_{3}\) has a secondary Carbon atom. So, the best representative for isoheptane is (c).

Key Concepts

Organic chemistry

Organic chemistry is the branch of chemistry that studies the structure, properties, composition, reactions, and synthesis of carbon-containing compounds. These compounds include not only hydrocarbons but also a vast range of molecules that consist of additional elements such as hydrogen, oxygen, nitrogen, sulfur, and halogens.
Organic chemistry is essential because all life on Earth is carbon-based, and understanding these molecules helps us comprehend biological processes and develop new materials, pharmaceuticals, and technologies.
In organic chemistry, compounds are often represented by chemical formulas that indicate the number and type of atoms involved. This representation simplifies the study of the complex structures and reactions. Fundamental to this field is understanding the behavior and interaction of different organic molecules, such as isoheptane, characterized by specific arrangements of their atoms. By mastering organic chemistry, students can unravel the mysteries of how different organic substances are formed and how they interact in various environments.

Hydrocarbons

Hydrocarbons are a large class of organic compounds consisting entirely of hydrogen and carbon. They form the basic framework for organic chemistry, and their study can provide important insights into the structure and behavior of more complex substances.
Hydrocarbons can be divided into several categories:

• Alkanes: Saturated hydrocarbons with only single bonds between carbon atoms, like isoheptane.
• Alkenes: Unsaturated hydrocarbons with one or more double bonds.
• Alkynes: Unsaturated hydrocarbons with one or more triple bonds.
• Aromatic hydrocarbons: Contain rings of bonded carbon atoms, such as benzene.

An alkane like isoheptane exhibits various structural isomers due to the different ways carbon atoms can connect, providing multiple possibilities for the same molecular formula. Understanding hydrocarbons is crucial because they make up fossil fuels, play a key role in energy production, and are foundational to understanding organic chemistry.

Chemical formulas

Chemical formulas are a concise way of expressing the components of a compound using symbols for the elements and numerical subscripts that show the ratio of each element.
For isoheptane, there are different ways to express its chemical formula:

• Molecular formula: Shows the total number of each type of atom, like \(C_7H_{16}\) for isoheptane.
• Structural formula: Depicts how atoms are arranged and connected, which for isoheptane can be expressed as \((CH_3)_2CH(CH_2)_3CH_3\).
• Condensed formula: Simplifies the structural formula, making it easier to write and understand.

A clear understanding of chemical formulas enables students to visually comprehend molecular structures and predict the behavior of the substance. This understanding is key in chemistry to determine reactivity, physical properties, and synthesis methods.

Isomers

Isomers are compounds that have the same molecular formula but different arrangements of atoms in space. This distinction can lead to varying physical and chemical properties within the same molecular formula family.
There are several types of isomers:

• Structural isomers: Differ in the connectivity of their atoms. Isoheptane is a structural isomer of heptane, where the atoms connect differently.
• Stereoisomers: Atoms are connected in the same order, but different spatial orientations.
• Geometric isomers: A type of stereoisomer caused by the restricted rotation around a bond, usually a double bond.

Understanding isomers is important not only for identifying different chemical behavior but also for applications in pharmaceuticals, whereby different isomers can have vastly different biological effects. In the case of isoheptane, the arrangement imparts specific physical properties that differentiate it from other isomers with the same molecular formula.