#1). No chemical process can account for the distribution of energy that we see coming from the sun. I mean the portions of the total that are radio waves, heat waves, light waves, x-rays, and gamma rays.
#2). A pile of the most energetic known chemicals, with the mass and volume of the sun, in the process of reactions and emitting energy, would have been burned out, all over and done with, long ago.
I read somewhere many years ago that a pile of coal the size of the sun could burn for 160 years. Even if it were ten million times as long as that, it would still be way short of the 4.6 billion years that the Earth has existed.
