I'm having trouble understanding:
O.Chem chpt. 2
Problem 8
The solution states that the answer is B because the methyl groups will not be competing for the space of the hydrogens, however, I thought B would be incorrect since the methyl groups are so close to each other, it would cause steric strain
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Good question! While the methyl groups are relatively close to each other, we won't have too much steric strain here. If you create a Newman projection down the bond between the two methyl groups, you'll see that they are actually gauche staggered. While this creates a bit of strain, it's still pretty small.
If you look at the other answer choices, C has a LOT of strain. The boat form of cyclohexane is quite unstable because of a large amount of nonbonded strain between the substituents on the carbons at the "points" of the boat. For A, while there is not much torsional strain, there is a lot of nonbonded strain with the other axial components of the cyclohexane.
In general, when you're looking at cyclohexane, equatorial is ALWAYS preferable. Since B gives us two methyl groups in the equatorial position, it's gotta be the most stable.
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Good question! While the methyl groups are relatively close to each other, we won't have too much steric strain here. If you create a Newman projection down the bond between the two methyl groups, you'll see that they are actually gauche staggered. While this creates a bit of strain, it's still pretty small.
If you look at the other answer choices, C has a LOT of strain. The boat form of cyclohexane is quite unstable because of a large amount of nonbonded strain between the substituents on the carbons at the "points" of the boat. For A, while there is not much torsional strain, there is a lot of nonbonded strain with the other axial components of the cyclohexane.
In general, when you're looking at cyclohexane, equatorial is ALWAYS preferable. Since B gives us two methyl groups in the equatorial position, it's gotta be the most stable.
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