Which of the following is the enantiomer of $2_1-\mathrm{chloropropane}$?

• A. $1_1-\mathrm{chloropropane}$, which is achiral
• B. $2_1-\mathrm{bromopropane}$
• C. The same molecule, $2_1-\mathrm{chloropropane}$, with identical configuration
• D. The mirror image of $2_1-\mathrm{chloropropane}$ with opposite configuration at the chiral center

Answer: (D)

Verified step by step guidance

1. Identify the chiral center in 2-1-chloropropane. This is the carbon atom bonded to the chlorine atom, which must have four different substituents to be chiral.
2. Understand that enantiomers are non-superimposable mirror images of each other, differing in the configuration (R or S) at the chiral center.
3. Recognize that 1-1-chloropropane is achiral because the carbon bonded to chlorine does not have four different groups, so it cannot be an enantiomer of 2-1-chloropropane.
4. Note that changing the halogen from chlorine to bromine (2-1-bromopropane) changes the substituent, so it is not an enantiomer but a different compound.
5. Conclude that the enantiomer of 2-1-chloropropane is its mirror image with the opposite configuration at the chiral center, meaning the stereochemistry (R or S) is inverted.