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Ch.23 - Organic and Biological Chemistry
Chapter 23, Problem 41

What is the difference in the chemical formula between a straight-chain alkane and a cycloalkane, each with the same number of carbon atoms?

Verified step by step guidance
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Step 1: Understand the general formula for straight-chain alkanes, which is C_nH_{2n+2}. This formula represents alkanes that are saturated hydrocarbons with single bonds between carbon atoms in a linear arrangement.
Step 2: Recognize the general formula for cycloalkanes, which is C_nH_{2n}. Cycloalkanes are also saturated hydrocarbons, but they form a closed ring structure, which affects the number of hydrogen atoms.
Step 3: Compare the two formulas: For a straight-chain alkane with n carbon atoms, the formula is C_nH_{2n+2}, while for a cycloalkane with the same number of carbon atoms, the formula is C_nH_{2n}.
Step 4: Identify the difference in hydrogen atoms: The straight-chain alkane has 2 more hydrogen atoms than the cycloalkane for the same number of carbon atoms.
Step 5: Conclude that the difference in the chemical formula between a straight-chain alkane and a cycloalkane with the same number of carbon atoms is the presence of 2 additional hydrogen atoms in the straight-chain alkane.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Alkanes

Alkanes are saturated hydrocarbons consisting only of carbon (C) and hydrogen (H) atoms, with single bonds between carbon atoms. Their general formula is CnH2n+2, where 'n' represents the number of carbon atoms. This structure allows for a maximum number of hydrogen atoms, making alkanes relatively stable and unreactive compared to other hydrocarbons.
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Cycloalkanes

Cycloalkanes are also saturated hydrocarbons but are characterized by a ring structure formed by carbon atoms. Their general formula is CnH2n, which indicates that they have two fewer hydrogen atoms than their straight-chain counterparts due to the formation of the ring. This difference in structure affects their physical and chemical properties, such as boiling points and reactivity.
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Structural Isomers

Structural isomers are compounds that have the same molecular formula but differ in the arrangement of atoms. In the case of alkanes and cycloalkanes, both can have the same number of carbon atoms, yet their distinct structures lead to different chemical formulas and properties. Understanding structural isomerism is crucial for distinguishing between these two classes of hydrocarbons.
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