[ChinaCat (OP)]

Hi all-- I'm teaching my 7th graders about organic and inorganic compounds and how carbon dioxide is actually classified as an inorganic compound, despite containing carbon. Naturally, they wanted to know why. I drew a complete blank... can anyone help me out? Thanks! []

[Ylide]

Carbon dioxide is is in kind of a "grey area" and really seems like it COULD be considered organic, but isn't.  On one hand, it contains carbon and is a common product in some organic reactions.  (combustion, respiration)  On the other hand, organic molecules are expected to be classified into certain categories based on functional groups and any molecule in one those categories is expected to react in a similar way to others like it.  CO2 does not have any of the typical organic functional groups...there is no other organic molecule that has one carbon double bonded to 2 other oxygens. (in fact, that's not possible to have that configuration in a different way than CO2)  Thus it doesn't fit into a family of organic compounds that react in the same way, and is not classified as such.  

Other examples of inorganic carbon-containing molcules are graphite/diamond and ionically bonded metal-carbines.

If you'd like a more formal definition, I believe it was explained to me years ago as any organic molecule must contain at least one carbon that has only covalent bonds and is in sp2 hydridization or greater.  (CO2, being linear is sp hybridized, and carbides are ionically bonded)

Hope that helped.

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[ChinaCat (OP)]

Awesome- that does clear it up for me... thanks!! []

[Chemistry4me]

Its a product of combustion