What are the 4 different types of chemical reactions?

Answer 1

I'll venture a guess...SN1, SN2, E1, E2, since it is an organic chemistry question. There are "four chemical mechanisms".

The General Chemistry answer for "classes of different reactions" is Addition, Decomposition, Single-replacement, and Double-replacement. These are the "kinds" of reactions out there. Red-ox, or combustion can be classified into one of those above.