Question

what is the general formula for straight-chain hydrocarbons with n carbon atoms and m (multiple) double bonds?

Answer 1

the formula:

$C_{a} H_{2a+2-2x}$

where

a - number of the carbon atoms

x - number of double bonds

We take as a example the hydrocarbon with 4 carbon atoms

x = 1 → $C_{4} H_{2*4+2-2*1}$ → $C_{4} H_{8}$

x = 2 → $C_{4} H_{2*4+2-2*2}$ → $C_{4} H_{6}$

x = 3 → $C_{4} H_{2*4+2-2*3}$ → $C_{4} H_{4}$