Originally Posted by scottland
Personally, I don't feel that you are 'destroying' volatile compounds with high temperatures. So once the wort is no longer boiling, I believe most of those compounds are staying in the wort. Cooling to 180*, should in theory only slow extraction.
The flash points for at least two of the major essential hop oils (myrcene & humulene) are 90F and 103F, respectively. So you are absolutely losing volatile compounds with high wort temperatures.
Isomerization of alpha acids (humulone, adhumulone, cohumulone, etc.) is still occuring above 180F, so there will be bitterness/flavor development, but the major drivers of aroma and to a lesser extent, certain aspects of hop flavor are lost. This is why a warm/cold hop stand may be beneficial, just as there is really no 1:1 substitue in the boil/hopstand for dry-hopping.