Reactivity, stability and energetics

[sigle]

I'm reviewing ochem right now and i feel silly for asking this but I cant make the conceptual leap between these terms.

For example, when describing cyclohexanes the chair conformations where the largest substituent are equitorial is the most favorable/stable conformations and also most reactive when compared to the axial positions.

I was under the assumption that the more reactive something is the less stable. I'm mixing up energetics with favorability and stability. What should I look at when deciding between two compounds reactivity? (Intermediates)
I hope that makes sense.



Thanks!

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[TieuBachHo]

I've skimmed the book over and found no direct conncection between most favorable conformation (equatorial position in this case) to the most reactive position. Maybe you have some sort of an extenuating case that couples with favorable conditions. If you don't mind, you can adduce examples/quotations from your gatherings.

However, I can understand under some conditions, a ring-flip can disguised the perceived judgement. Others may have better explanation than this.

 

[RogueUnicorn]

the more stable compound will always be less reactive when discussing the same reactions. remember, though that KINETICS and THERMODYNAMICS are entirely separate concepts - a less favorable reaction can easily be faster than a more favored reaction. i imagine this could be a source of your confusion.

 

[boaz]

the more stable compound will always be less reactive when discussing the same reactions. remember, though that KINETICS and THERMODYNAMICS are entirely separate concepts - a less favorable reaction can easily be faster than a more favored reaction. i imagine this could be a source of your confusion.

I think the source of confusion is that the word "stability" is used in discussion of kinetics as well as thermodynamics. It is important to remember that whereas in thermodynamics discussions of "stability" always refer to the products/reactants, in kinetics the term always refers to the transition state. The more stable (lower energy) the transition state, the faster the reaction.