Which of the following molecules possesses a plane of symmetry?

• A. $2-\mathrm{butanol}$
• B. $2,3-\mathrm{dibromobutane}$
• C. $\mathrm{cyclohexane} \mathrm{in} \mathrm{chair} \mathrm{conformation}$
• D. $2-\mathrm{methylpentane}$

Answer: (B)

Verified step by step guidance

1. Understand the concept of a plane of symmetry: A molecule has a plane of symmetry if it can be divided into two mirror-image halves. This means that one half of the molecule is a mirror reflection of the other half.
2. Analyze 2-butanol: Draw the structure of 2-butanol and try to identify if there is any plane that divides the molecule into two symmetrical halves. Consider the arrangement of the hydroxyl group and the carbon chain.
3. Examine 2,3-dibromobutane: Draw the structure of 2,3-dibromobutane. Look for a plane that can divide the molecule into two equal halves. Pay attention to the positions of the bromine atoms and the carbon backbone.
4. Consider cyclohexane in chair conformation: Draw the chair conformation of cyclohexane. Determine if there is a plane of symmetry by considering the positions of the hydrogen atoms and the overall shape of the chair conformation.
5. Evaluate 2-methylpentane: Draw the structure of 2-methylpentane. Check for any plane that can divide the molecule into two symmetrical halves, considering the branching of the carbon chain.