I recently saw a request for solids that auto-ignite between 80C and 160C. I can't find any, and none have yet been suggested.
Which leads me to the theoretical question: Is it possible for there to be gaps in auto-ignition temperature ranges that cannot be filled by any chemical?
More specifically: Supposed we're interested in auto-ignition of a chemical in a standard atmosphere (where the temperature is varied between storage and ignition).
First question: Is it true that any chemical that can auto-ignite in a given atmosphere at some temperature will not be shelf-stable when stored in that atmosphere at any temperature? Or are there self-sustaining exothermic reactions that will not occur at all below a threshold (auto-ignition) temperature, and therefore would be indefinitely "shelf-stable"?
Second question: If shelf-stable auto-ignition is possible (or even typical), then are there any theoretical assertions that can be made about the possibility of auto-ignition temperature gaps? E.g., if I know there is a chemical that auto-ignites at 20C, should it theoretically be possible to chemically dampen the reaction so as to raise the auto-ignition temperature arbitrarily? Or is this just a "that's the way it is" property? I.e., chemicals have the reactivity they have, and there's no reason to believe that you could pick an arbitrary temperature and find a compound that auto-ignites at that temperature?