Which of the following cycloalkanes would you expect to produce the least heat upon combustion when measured per CH₂? Explain your answer.

Verified step by step guidance

1. Understand the concept: The heat of combustion is a measure of the energy released when a compound is burned completely in oxygen. For cycloalkanes, the amount of heat released is influenced by the ring strain. Cycloalkanes with less ring strain are more stable and release less heat upon combustion.
2. Recall the relationship between ring strain and stability: Smaller rings (e.g., cyclopropane and cyclobutane) have higher ring strain due to angle strain and torsional strain. Larger rings (e.g., cyclohexane) tend to have less ring strain because they can adopt conformations that minimize these strains.
3. Compare the cycloalkanes: Evaluate the ring strain for each cycloalkane in the list. Cyclohexane, for example, adopts a chair conformation that minimizes strain, making it more stable. Cyclopropane and cyclobutane, on the other hand, have significant angle strain and torsional strain, making them less stable.
4. Relate stability to heat of combustion: The more stable the cycloalkane, the less energy is released during combustion. Therefore, the cycloalkane with the least ring strain will produce the least heat upon combustion.
5. Conclude based on the analysis: Identify the cycloalkane with the least ring strain (likely cyclohexane) and explain why it produces the least heat upon combustion compared to the others in the list.

Key Concepts

Cycloalkanes

Cycloalkanes are saturated hydrocarbons that contain carbon atoms arranged in a ring structure. They are characterized by the general formula CnH2n, where 'n' is the number of carbon atoms. The stability and reactivity of cycloalkanes can vary based on their size and the presence of substituents, which influences their combustion properties.

Combustion Reaction

A combustion reaction is a chemical process in which a substance reacts rapidly with oxygen, producing heat and light. In organic chemistry, the combustion of hydrocarbons typically results in carbon dioxide and water as products. The amount of heat released during combustion, known as the heat of combustion, depends on the structure of the molecule and the number of carbon and hydrogen atoms present.

Heat of Combustion

The heat of combustion is the energy released when a substance undergoes complete combustion with oxygen. It is usually expressed in kilojoules per mole (kJ/mol). For cycloalkanes, the heat of combustion can vary based on factors such as ring strain and molecular stability; cycloalkanes with more strain or fewer hydrogen atoms typically release less heat upon combustion.