Question

What is the chemical structure for Smoke ?

Answer 1

If you're talking about smoke from a wood fire:
The constituents of (things that make up) wood is mostly comprised (made up) of the compund:
\[C_{10} H_{15} O_7\]
This means it is 10 parts Carbon, 15 parts Hydrogen, and 7 parts Oxygen
Adding heat produces the equation:
\[6C_{10} H_{15} O_7 \rightarrow C_{50} H_{10}+10CH_2 O\]
(Note that this is not balanced: I've omitted (left out) some boring by-products)
Which means that, in the presence of heat, wood produces char and a certain gassy substance. This gassy substance then promptlyl undergoes the reaction with the oxygen (gas) in the air:
\[CH_2 O+O_2\rightarrow H_2 O + CO_2 + CO + C + N_2\]
Which is what we see. So in answer to your question, smoke is comprised of water carbon dioxide, carbon monoxide, carbon (solid, particles) and nitrogen gas

Answer 2

What about the Smoke coming from those Cars ?