Which of the following compounds is a $\mathrm{cycloalkene}$?

• A. $\mathrm{cyclobutane}$
• B. $\mathrm{cyclohexane}$
• C. $\mathrm{cyclopentene}$
• D. $\mathrm{cyclopropane}$

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the definition of a cycloalkene. A cycloalkene is a cyclic hydrocarbon that contains at least one carbon-carbon double bond (C=C) within the ring structure.
2. Step 2: Examine each compound's name to identify whether it contains a double bond. For example, names ending with '-ene' indicate the presence of a double bond, while '-ane' indicates only single bonds.
3. Step 3: Analyze the given compounds: 'cyclobutane' and 'cyclohexane' both end with '-ane', meaning they are saturated rings with only single bonds; 'cyclopentene' ends with '-ene', indicating a double bond; 'cyclopropane' also ends with '-ane', so it has only single bonds.
4. Step 4: Confirm that 'cyclopentene' is a five-membered ring with one double bond, fitting the definition of a cycloalkene.
5. Step 5: Conclude that among the options, 'cyclopentene' is the cycloalkene because it contains a carbon-carbon double bond in a cyclic structure.