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Multiple Choice
Which of the following molecules is chiral?
A
2-butanol
B
ethanol
C
acetone
D
2-propanol
Verified step by step guidance
1
Understand the concept of chirality: A molecule is chiral if it has a non-superimposable mirror image, often due to the presence of an asymmetric carbon atom (a carbon atom bonded to four different groups).
Examine each molecule to identify any asymmetric carbon atoms. Start with 2-butanol: The structure of 2-butanol is CH₃CH(OH)CH₂CH₃. The second carbon atom is bonded to four different groups: a methyl group (CH₃), a hydroxyl group (OH), an ethyl group (CH₂CH₃), and a hydrogen atom (H). This makes it chiral.
Analyze ethanol: The structure of ethanol is CH₃CH₂OH. The carbon atoms are bonded to identical groups (hydrogens and a hydroxyl group), so there is no asymmetric carbon atom, making ethanol achiral.
Consider acetone: The structure of acetone is (CH₃)₂CO. The central carbon atom is bonded to two identical methyl groups (CH₃) and an oxygen atom, lacking an asymmetric carbon, thus acetone is achiral.
Evaluate 2-propanol: The structure of 2-propanol is CH₃CH(OH)CH₃. The central carbon atom is bonded to two identical methyl groups (CH₃), a hydroxyl group (OH), and a hydrogen atom (H), which does not create an asymmetric carbon, making 2-propanol achiral.