Talk:Isomer
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Does the definition of "isomerism" require "the same kinds of bonds between atoms"? I would have said that, say, benzene and prismane are isomers. And is it true that "isomers typically share similar if not identical properties in most chemical contexts"? In fact the examples given in the history section seem to belie both of these claims.
- Josh Cherry 22:18, 13 Oct 2003 (UTC)
I wrote both those statements and I definitely wasn't thinking of prismane, which does seem to disprove the rule. On the other hand, I think a qualifier like "typically" or "generally" covers a multiple of ills. Since you pulled the example of prismane out of the air, I suspect you know more chemistry than me. If prismane is one of a relatively narrow category of exceptions (I don't know), then to me I think "typically" still cuts the mustard. I think the priority should be to convey information and not to construct all inclusive definitions. In other words, if rules of thumb exist, I think we should tell people. I arrived at "the same kinds of bonds between atoms" by thinking of a simple ketone or alcohol or halagonated alkane. I couldn't think of an isomer of one of those where you wouldn't still have a "C" double-bonded to "O", then I thought of the electron shell filling principle, and from there I jumped to my rule of thumb. But if you give a couple not too bizarre examples besides prismane, you'll convince me that I was mentally impaired. My motive in concocting this rule-of-thumb statement about isomers was my intuition that a reader who knows even less chemistry than I is likely to assume that there's no limit to the number of ways that a given set of atoms can bond to form a stable molecule--such that isomers (defined only as sharing the same chemical forumla) are unlikely to be more than trivially related--whereas actually something closer to the reverse is true. 168... 00:27, 14 Oct 2003 (UTC)
I don't think prismane/benzene is especially bizarre. Here are a few other isomer pairs to consider:
- Cyclohexane and any acyclic hexene
- Any ketone and its enol tautomer
- Lactic acid and glyceraldehyde
- H2C=C=CH2 and methyl acetylene
- Some organic sulfate and some sulfide isomer with the oxygens put into hydroxyl groups or something
Josh Cherry 01:44, 14 Oct 2003 (UTC)
O.K.. I can't remember o-chem but I think I recognize when I see it. I just weakened the intro generalizations. Does that work for you? I think one of your examples above with a figure would be good to add somewhere below the intial one to illustrate how the intro generalizations do not always apply.168... 03:25, 14 Oct 2003 (UTC)