MM2 Energy

[irisc23]

What does the MM2 energy measure, and what is this energy relative to? I thought that the MM2 energy was supposed to be potential energy relative to the most stable structure (i.e. the most stable structure should have 0 kJ/mol), as we were told in lecture; however, when I ran the MM2 for chair cyclohexane (the most stable form of cyclohexane) the energy was not 0. Why is that, and how is this energy actually measured? Thank you very much.

[ch1995]

http://ww2.chemistry.gatech.edu/class/2 ... comp02.pdf
^Looking at this, I think the MM2 energy includes energy for bond stretching, angle bending, etc. Since the angle for chair conformation is 110.9* (pg 112 of organic chem txtbook) instead of the optimal 109.5, maybe this angle bending (among other factors) causes the MM2 value not to be 0?

[irisc23]

So... is the energy relative to hexane then? Or is it relative to formation (i.e. the potential energy difference between the reactants in standard state and the molecule)? The methyl halides all had 0 potential energy (in accordance to the fact that bond angles were not stretched), but some of the functional groups also had nonzero values, and they definitely did not have bond angle stretching.