Identify the More Stable Stereoisomer

Which stereoisomer is more stable in the pair cis-1-isopropyl-2-methylcyclohexane?

a) Isomer 1; Steric hindrance is minimized.

b) Isomer 1; Dipole-dipole interactions are maximized.

c) Isomer 2; Steric hindrance is minimized.

d) Isomer 2; Dipole-dipole interactions are maximized.

Answer

The more stable stereoisomer is the trans isomer of 1-isopropyl-2-methylcyclohexane due to minimized steric hindrance when the bulky groups are on opposite sides.

Explanation: To identify the more stable stereoisomer between cis-1-isopropyl-2-methylcyclohexane isomers, we must consider the factors affecting stability. Steric hindrance plays a significant role in the stability of cycloalkanes due to the constrained cyclic structure.

For this particular molecule, the trans isomer would be more stable because in the cis isomer the two bulky groups (isopropyl and methyl) are on the same side of the cyclohexane ring causing increased steric hindrance. In contrast, in the trans isomer, these groups are on opposite sides, which reduces the steric strain on the molecule. Therefore, the correct answer is c) Isomer 2; Steric hindrance is minimized.

Dipole-dipole interactions are not a determining factor in this case because both isopropyl and methyl groups are nonpolar. Hence, we do not consider option b) or option d) as part of our reasoning.