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All organic matter seems to be inflammable when dried up. Petroleum, Alcohol, Wood, and Coal burns readily. Can I call it a general rule? Are there known exceptions? What makes them the exceptions?

Aniruddha Sarkar
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    Freons don't burn. – Ivan Neretin Mar 06 '20 at 05:58
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    @IvanNeretin - Freons aren't really "organic." – MaxW Mar 06 '20 at 06:21
  • Loosely related: Are there substances that cannot undergo combustion? – andselisk Mar 06 '20 at 06:58
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    @MaxW What's really organic, then? Does it have to be retrieved from a living body? Well, bones don't burn. – Ivan Neretin Mar 06 '20 at 07:04
  • Yes all organic compounds can burn. Flammability is another issue. But in proper (hard) conditions everything containing carbon-carbon in principle undergo combustion. Still, a piece of Teflon is not easily lit. – Alchimista Mar 06 '20 at 07:31
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    Burning an organic substance is the standard way of analyzing it. The substance is mixed with Copper oxide in a tube heated in a currant of O2. The gas getting out of the tube is analyzed for its CO2 and H2O content. This is the standard way all organic substances have been analyzed. – Maurice Mar 06 '20 at 09:32
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    @Maurice It was standard, like a century ago. Not all was, or can be analysed like this. For example trying to do this with teflon wouldn't be good idea (not to say it wouldn't work). https://chemistry.stackexchange.com/questions/34190/is-there-any-chemical-that-can-destroy-ptfe-or-teflon – Mithoron Mar 06 '20 at 20:03
  • https://chemistry.stackexchange.com/questions/119887/are-all-volatile-liquids-combustible – Mithoron Mar 06 '20 at 20:12

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Burning is a non-scientific term, it implies appearance of a luminous chemical reaction in a gaseous phase. It is commonly called a flame. It does not necessarily imply the presence of carbon or even oxygen. Boron and hydrogen compounds can burn in air, similarly, sodium burns in the presence of chlorine.

You can rather ask, can I oxidize carbon containing materials to carbon dioxide or carbon monoxide in the presence of oxygen? The general answer is yes. You already mentioned the examples of wood, sugar, coal etc. which are carbon rich materials. They will burn with a luminous flame. The carbon in inorganic materials such as refractory carbides, like silicon carbide, can also be oxidized that but only under extreme conditions.

IUPAC acknowledges that the "The boundaries between ‘organic’ and ‘inorganic’ compounds are blurred." So there is no need to create an arbitrary division.

AChem
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