The first thing to note is that what drives off volatile compounds is threefold: agitation (as in boiling), heat (as in boiling) and time. It's the combination of these that does the most damage.
Pasteurization doesn't require boiling. The elements of pasteurization are heat and time (and, incidentally viscosity, which is an important consideration for milk pasteurization). You can pasteurize for less time with more heat, or pasteurize with less heat in more time. The actual balance has been nicely laid out for us by milk producers who had a little problem with tuberculosis and raw milk about 100 years ago. For milk, the standard is 145°F (62.8°C) for 30 minutes, or 161°F (71.7°C) for 15 seconds. Mead wort, being much less viscous than milk, requires either less heat or less time or a little less of both.
What I'm proposing follows. (FYI, you can substitute a US gallon for 4 litres, roughly. I mention that in order that it's easily useful for both US and UK members.)
1. The day before brewing, boil 12 litres of water, cool, then pour into three 4-litre (or US gallon) jugs. Refrigerate overnight.
2. On brew day, boil 8 litres of water, with whatever yeast nutrients, acids, tannins etc that you planned for your mead. Boil for 5 minutes and remove from heat.
3. Add 12 pounds of honey, stir well without aerating much, return the lid to the pot, and cover the pot with some towels to insulate. The resulting liquid should be around 155°F. How do I know that? 8 litres at 1 kg/litre weighs 8 * 2.2 = 17.6 lbs. The 12 pounds of honey are at around 72°F, room temperature. And finally:
4. Leave this covered and insulated for 15 minutes to pasteurize, then force cool.
5. While it's cooling, pour 8 litres of the refrigerated boiled water into you fermenter (reserve the last 4 litres for topping up). When the honey wort has cooled to around 100 to 110°F, pour it into the fermenter over the cold water. Stir. (Note: pouring into the fermenter should provide enough aeration. If you're a bit nervous about that, put a tiny drop of olive oil into a thimble of vodka, dissolve, then into the boil. Why? Sterols. That's another story.)
6. Top up with the reserved water, as required and stir a bit more.
What's just happened here? You've pasteurized your honey wort for a short time (not long enough to drive off volatiles at that temperature) and with a temperature much lower than boiling (not hot enough to drive off volatiles in that short time).
And you didn't need any chemicals, which, being bad for microbes, aren't great for you either. That's how we do it chez Laripu.
Now go and sin no more.