Which of the following chemical formulas represents an asymmetrical ($\mathrm{chiral}$) molecule?

• A. $C_2{H}_4$ (ethylene)
• B. $C_2{H}_6$ (ethane)
• C. ${\mathrm{CH}}_3\mathrm{CHBrClF}$ (2-bromo-2-chloro-2-fluoropropane)
• D. ${\mathrm{CH}}_4$ (methane)

Answer: (C)

Verified step by step guidance

1. Understand that a chiral molecule is one that is not superimposable on its mirror image, often due to the presence of a carbon atom bonded to four different substituents (a stereogenic center).
2. Examine each given molecular formula and identify if there is a carbon atom bonded to four different groups, which is necessary for chirality.
3. For ethylene (C\2H\4) and ethane (C\2H\6), note that their carbons are bonded to identical groups (hydrogens or carbons), so they lack a stereogenic center and are achiral.
4. For methane (CH\4), the single carbon is bonded to four identical hydrogens, so it is also achiral.
5. For 2-bromo-2-chloro-2-fluoropropane (CH\3CHBrClF), focus on the carbon bonded to Br, Cl, F, and CH\3 groups; since these four substituents are all different, this carbon is a stereogenic center, making the molecule chiral.