Which of the following statements best describes a meso compound?

• A. It is a chiral compound with no plane of symmetry and at least one $\mathrm{stereocenter}$.
• B. It is a racemic mixture of two $\mathrm{enantiomers}$ in equal proportions.
• C. It is an achiral compound that contains two or more $\mathrm{stereocenters}$ and has an internal plane of symmetry.
• D. It is a compound with no $\mathrm{stereocenters}$ and is always optically active.

Answer: (C)

Verified step by step guidance

1. Understand the definition of a meso compound: it is a molecule that contains two or more stereocenters but is overall achiral due to an internal plane of symmetry.
2. Recall that chirality arises when a molecule lacks an internal plane of symmetry and has non-superimposable mirror images (enantiomers).
3. Recognize that a meso compound, despite having stereocenters, is achiral because the internal symmetry causes the molecule to be superimposable on its mirror image.
4. Differentiate meso compounds from racemic mixtures, which are 1:1 mixtures of enantiomers and not single molecules with internal symmetry.
5. Note that compounds with no stereocenters cannot be meso compounds, and meso compounds are not optically active due to their achirality.