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Name: doug happ
Status: N/A
Age: N/A
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Date: 1999 

I teach sophomores an introductory biology course. When I cover the biochemistry section the terms organic and inorganic come up. I am not satisfied with the simplistic statement that organic chemicals are ones that contain carbon since it does not account for carbon dioxide being an inorganic. Is there a definition of 'organic chemical' which accounts for all or most molecules?

Given the existence of hemoglobin, "zinc fingers" in some enzymes, and buckyballs, I'd guess not.

christopher grayce

Considering the number of carbon containing molecules that ARE considered to be organic relative to the number that are NOT, the rule that an organic molecule is one that contains carbon, works VERY well. The "exceptions" might serve as a lead-in to a discussion of the use of rules, such as classifying molecules as organic or inorganic, as a contrived convenience. They are helpful for most cases. In the cases where the rules don't work well we have to be able to turn to other tools, such as an understanding of chemical bonds or molecular orbitals so we can concentrate on the characteristic of interest -- which is very rarely whether the molecule is organic or more often things like reactivity. You're at the leading edge of helping these students think for themselves in a field where they probably feel unsure of themselves! It sounds like you have some inquiring students there and some active discussions. May you have many more!


An interesting question. I believe that "organic" vs. "inorganic" originally stemmed from the ancient idea that compounds could be divided into two categories; those isolated from plants and animals (organic) and those extracted from minerals and ores (inorganic). [source: Bodner and Pardue, Chemistry: An Experimental Science, 1993].

As a working definition, now we think of organic chemistry as primarily being the chemistry of carbon-containing compounds. Most carbon-containing compounds have one or more of the following: H,N,O,S,P. Some authors describe organic chemistry as the study of compounds that contain carbon and hydrogen. By this definition, CO2 would be "inorganic." But I would like to stress that in fact there is no general agreement on such semantics, and I'd bet that a lot of chemists consider CO2 to be "organic" because it contains C and O.

My $0.02.


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