First, why don't you give a try with your first part of your question to the organic forum. People will be more likely to respond to it there.
For the second part of your question, here's what happens:
2 Cu + O2 --> 2 CuO
The elemental copper powder reacts with the oxygen in the air to form copper (II) oxide. I say copper (II) oxide because copper (I) oxide is red and you describe a black substance. Copper (II) oxide is black.
Now, when heating pennies, ordinarily, you just get the reaction above. However, with the color change you're talking about, you have to first soak the penny in a solution of concentrated NaOH and Zn, to form the sodium zincate complex:
This complex forms on the outside of the penny, and when you heat it, the copper and the zincate complex combine to form brass, which is the shiny silvery/gold color. It's pretty cool, actually.