[AlbertoA]

I have this problem, the reaction is between 1,4-dimethyl cyclohexene with H2SO4 and H2O, so, it's an Electophilic addition, the H2O can attack from both sides, giving two products, one with the OH in axial position and the other with an ecuatorial OH

the A value for OH is less than the CH3, so, the cyclohexane with the Axial OH will be more stable than the cyclohexane with the equatorial OH.

This is the problem, the answer says that the axial OH will form hydrogen bond with the 1,3 Hydrogens (Whiskey Tango Foxtrot???) so, the cyclohexane with the Axial ch3 and equatorial OH is more stable

the answer seems wrong, any idea?

[Vidya]

formation of hydrogen bonds will increase the stability

[BluePill]

That is contradicting.

[orgopete]

That is a good question, but the answer does not depend on the A-values. That is, if you were to compare the preferred conformations of 1-methylcyclohexanol, then it would be as predicted, axial OH. However, that is not the question in this case.

The question asks for you to predict the product ratio of a reaction. The product would have two equatorial substitutents in the preferred conformation. That gives two choices, either the OH or the CH3 is axial. However, this is a reaction. The question is, "Will the preferred conformation (axial OH) lead to the most stable product?" Because the product is a tertiary alcohol in sulfuric acid, I argue the reaction can equilibrate to the most stable product. Therefore, I can imagine two factors involved. First, the group at equilibrium is not necessarily an ROH, but rather an ROH2(+). Secondly, the rate of elimination of water from axial and equatorial should also be considered. If the elimination of an axial water is much faster than equatorial, then the equilibrium would result in the equatorial alcohol. That is my preferred rationale.

[AlbertoA]

That is a good question, but the answer does not depend on the A-values. That is, if you were to compare the preferred conformations of 1-methylcyclohexanol, then it would be as predicted, axial OH. However, that is not the question in this case.

The question asks for you to predict the product ratio of a reaction. The product would have two equatorial substitutents in the preferred conformation. That gives two choices, either the OH or the CH3 is axial. However, this is a reaction. The question is, "Will the preferred conformation (axial OH) lead to the most stable product?" Because the product is a tertiary alcohol in sulfuric acid, I argue the reaction can equilibrate to the most stable product. Therefore, I can imagine two factors involved. First, the group at equilibrium is not necessarily an ROH, but rather an ROH2(+). Secondly, the rate of elimination of water from axial and equatorial should also be considered. If the elimination of an axial water is much faster than equatorial, then the equilibrium would result in the equatorial alcohol. That is my preferred rationale.

equilibrium between what?
elimination of water... doesn't it produce an alkene?
don't you mean elimination of H+?

[orgopete]

If you take t-butanol, you can dehydrate to form isobutene with sulfuric acid. You can take isobutene, sulfuric acid and water to make t-butanol. There is an equilibrium between the alcohol, alkene, and the tertiary carbocation intermediate. Water favors alcohol formation. Removal favors alkene.

I think the carbocation should be the intermediate, no? Water could add to it from either side. Elimination of water (to form the carbocation) can have different rates if it is axial than equatorial.

You needn't invoke an E2 elimination, therefore the first step would be formation of the carbocation, an E1/SN1 step. If a proton is lost to reform the cyclohexene, it should still participate in the forward reaction, namely protonation and then addition of water. Also, under strongly acidic conditions, deprotonation will be suppressed. While some E1 mechanism can (and probably does) operate in this reaction, the conditions are such that it would be difficult to identify this process unless some labeling were incorporated into the experiment.