[ScorchedEarth87]

For a question from my practice midterm I'm suppose to draw the meso and R,R configurations of 2,2,3,4,5,5 of hexamethylhexane. Which I didn't have a problem with, but my professor then asks which would give off more heat when burning 1 mole of the compound, the R,R, or meso?

I know if they're in an achiral environment they would have the same properities...but I'm pretty sure oxygen isn't achiral. So can someone please help me, I'm really stuck here. Thanks.

[movies]

If the two compounds in question were enantiomers then their properties in an achiral environment would be identical, but these two compounds are diastereomers and in principle have different properties.  Draw out some of the possible rotamers of these two compounds and pick which conformation will have the lowest energy for each compound.  You'll find that in one case the lowest energy rotamer will have fewer steric interactions than the lowest energy rotamer of the other diastereomer.

[ScorchedEarth87]

thank you