An organic compound that burns with a sooty flame is most likely an unsaturated compound. Here's why:

* Sooty Flame: A sooty flame indicates incomplete combustion. This means there's not enough oxygen to fully oxidize the fuel (the organic compound).

* Unsaturated Compounds: Unsaturated compounds have carbon-carbon double or triple bonds. These bonds contain a higher concentration of electrons, making them more reactive and prone to incomplete combustion.

* Saturated Compounds: Saturated compounds have only single bonds between carbon atoms. They are less reactive and burn more cleanly, producing less soot.

Examples:

* Unsaturated: Ethylene (C₂H₄), acetylene (C₂H₂) - These compounds burn with a sooty flame due to the presence of double and triple bonds.

* Saturated: Methane (CH₄), ethane (C₂H₆) - These compounds burn with a cleaner flame due to the presence of only single bonds.

Note: While a sooty flame is a strong indicator of an unsaturated compound, it's not always conclusive. Other factors, like the amount of oxygen available, can also influence the flame's appearance.