[Tubulin]

So I've got a course in molecular modelling and need to finish up a report for a computer exercise. A part of the exercise involved optimizing a chair and boat structure of cyclohexane and calculating their molecular energies. All this was done with Tinker and WebMo. I got all the energies with no problem, but the theory question is: "Explain how the difference in strain energy relates to the difference in enthalpy, which is measured to 5.5 kcal/mol. Point out the relationship between enthalpy and strain energy, and to what extent the difference in strain and/or steric energy between the conformations may be used to estimate the difference in enthalpy."

If I am correct the strain energy is equal to the energies of the bonded interactions (bend, stretch, angle etc.) but not the non-bonded interactions, while the steric energies are equal to the strain energy + non-bonded energies like vdW and electrostatic (which I guess are negligible since it is a hydrocarbon). Using my reasoning above, I've calculated that the difference in strain energy is: 4.7836 kcal/mol, while the difference in steric energy is: 5.7595 kcal/mol

As I mentioned above, I've assumed the electrostatic interactions are negligible, and those where not included i the Molecular Energies values made by Tinker.

My thought is that the difference in enthalpy does not include the electrostatic interactions or van der Waals interactions, and therefore the change in strain energy should in theory be equal to the change in enthalpy. But I'm really unsure about it, and the rest of the question.

Thanks in advance for any answers.

[curiouscat]

When you compare individual molecules it shouldn't account for any intermolecular interactions.