Talk:August Kekulé

Reference
--Stone 09:28, 12 March 2007 (UTC)

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HIO4 example
I have reworded this example to make clear that it is the chain structure is based on Kekule's ideas and not the correct structure. But I also have some historical questions:

Who proposed the chain structure and when? Kekule himself? Someone else prior to 1912 (when crystallography started)? Or a more recent textbook looking for examples where Kekule's ideas give the wrong structure?

If the chain structure was criticized prior to 1912, on what grounds was it criticized then? Of course, it was easy to criticize in Pauling's era (1930s) after the correct structure was known from crystallography. As it is easy for modern students who have learned about VSEPR and orbital hybridization. Dirac66 00:34, 31 October 2007 (UTC)


 * The structure was proposed before 1882, when Kolbe heavily critizised it, not on the basis of something better, but on the basis that the people proposing the structures also had not the slightes clue what a benzene ring or periodic acid look like. The chemistry of periodic acid showed no sign of different oxygens, which would be the case in the linear structure. (Kekule made this asumption in the question of disubstituted benzenes, that the disstance between the substituents makes the substance behave different) Kolbe and a few other chemists refused to make the step from chemical reactivity and experimental results to conclude the structure of a molecule, because this hypothesis was possible to disprove.--Stone 18:26, 31 October 2007 (UTC)

Ah yes. I had forgotten the nature of 19th-century chemical reasoning before crystallography and other physical methods. I think though that your last 3 words "possible to disprove" should be "impossible to disprove (at the time)". I think now we can try to improve the article by explaining briefly the nature of Kolbe's criticism. The focus should remain on Kekule however since it is his article. Dirac66 03:30, 1 November 2007 (UTC)

Right! impossible! We should focus on Kekule! The criticism was strong in the beginning and by 1882 when Kolbe still refused to belive that the structure of molecules should be drawn on paper the critical voices nearly deminished. The step to get the structure of the molecule only from chemical reactions and pysical measurments of bulk properties of the substances is even for me loking back a big step! It gave a lot of wrong answers, but chemistry without it would have never made the progress we saw between 1860 and 1912. --Stone 08:14, 1 November 2007 (UTC)

I have now reworded the paragraph about HIO4 to include some of your explanations. What do you think of the following text (which I have not yet put in the article)?

The idea of a fixed number of valences for each element was one key component of the structural chemistry. This concept has proven to be wrong, especially in inorganic chemistry, and was subsequently replaced by fixed valences for each oxidation state. One often criticized example was periodic acid, HIO4. According to Kekule's ideas, iodine has one valence, oxygen two and hydrogen one, leading to an (incorrect) chain structure I-O-O-O-O-H, with each oxygen at a different distance from the iodine. In 1882 Kolbe criticized this structure (and Kekule's theory) because the chemistry of periodic acid shows no sign of inequivalent oxygens. Modern chemists realize that iodine in this molecule has seven valence (corresponding to its oxidation state), and that the correct structure has all four oxygen atoms surrounding the iodine in a tetrahedral geometry. In defence of Kekule, however, it must be noted that fixed valences are more usual in organic chemistry. Dirac66 01:41, 4 November 2007 (UTC)

HIO4 example revisited
I have several comments (I am the author of the only book-length modern biography of Kolbe). First, Dirac66 is right that Kekule's idea was not based on direct observations of atoms and molecules, but no chemist could do that then. No chemist can do that even today, one might legitimately say, because x-ray crystallography does not "directly observe" molecules, either. In both cases one needs to make inferences from macroscopic evidence which is gathered more or less indirectly. But Kekule's work WAS based on "direct observations", namely observations of many chemical reactions and physical properties that led him (legitimately!) to the conclusions about valence and structure theory that the article describes. So I would argue that the first paragraph of this section is a little misleading.


 * Kolbe was accusing Kekule to go one step to far. He points out that the true inner structure and the real constitution of a molecule will always be hidden and unreachable like the moon, and that the radical theory is enough to work with. —Preceding unsigned comment added by Stone (talk • contribs)

Second, Kolbe was indeed an experimental chemist, but he was also (and really much more) a theoretical chemist too. Kekule was both experimental and theoretical, as well. Kolbe's objection was not that one could not form a theory about such matters (HE certainly had formed very many!), but rather that Kekule's particular theory was incorrect. But the most important point to keep in mind is that Kolbe had become so rabid and so abusive in his published critiques, that by 1882 no one really paid him any mind. I am quite sure that Kolbe had come to suffer some kind of personality disorder or mania, and most in the profession knew that. So I'm not sure that mentioning Kolbe's 1882 critique is really very relevant here. (By the way, do you have a reference for that critique? I don't know it offhand, and would like to look it up.)


 * His tone was showing kind of mental distortion. The attack on french chemists, the french chemical society and Baeyer show that he lost track in the lat years of his life and that the crtic on Kekule was only done to have a good fight with someone. His arguments do not lack good scientific points and that he thought the theory is incorrect is the wrong word, more likely to empirical and not based on science and observation, but on thoughts. —Preceding unsigned comment added by Stone (talk • contribs)

Third, I am virtually certain that Kekule never proposed the sort of chaining formula for periodic acid that is mentioned here. Others did, following Kekule, but since this is a biography of Kekule and not a discussion of the history of structure theory, I don't think it belongs here.


 * He neverproposed this kind of structure, but he was the point of critizism, because he was the most prominent member of the structural chemists. —Preceding unsigned comment added by Stone (talk • contribs)

It is absolutely true that Kekule strongly supported constant valence, which led to such ideas. So I think it is relevant to include something about this in the article. The section written by Dirac66 makes some good points, and I do not mean to suggest that it is all incorrect. But doesn't it really belong in historical section of the article on structure theory, rather than in the biographical article on Kekule?


 * The personal way of Kolbe to accuse Kekule to be unscientific and proposing emirical unprovable science was harsh and personal. The real personal fight between Kolbe and Kekule, Baeyer, Berteloth and others is a point which could go into the biography of Kekule. —Preceding unsigned comment added by Stone (talk • contribs)

In my opinion, the rewrite offered by Dirac66 is an improvement, but still suffers from some of the same disadvantages. I commend Dirac66, but I believe that this material is better suited for a general history of chemistry, not for the biographical article on Kekule. Too much of it pertains to a period after Kekule's death. Kekule actually stopped publishing new research about 1870, anyway, so even the last 25 years of his life were not very active. The modern idea of oxidation states is not relevant to the biography. It should not be the purpose of an article on a historical figure in science to point out where that figure had it wrong (from a modern perspective).


 * That he suffered from critics which basically ended after the death of Kolbe and turned out to a nearly 100% victory is worth mentioning! (point out where that figure had it wrong) Why? The Stahl article states obsolete phlogiston theory and this also states that he was wrong! —Preceding unsigned comment added by Stone (talk • contribs)

I would like to ask Dirac66 and Stone whether they would object if the paragraph were deleted? As I say, much of the material in it would be valuable in another Wikipedia article. Ajrocke 16:04, 6 November 2007 (UTC)


 * Deletion is never an option! To start a new article, move it, change it, or do something else is perfectly fine with me, but to delete a paragraph which is not wrong is not very wiki like!
 * Please change it in a way that its is more clear and if necessary move it to a better place im confident that you will do a good job! I will also try to improve it, but the next days I am busy!--21:06, 6 November 2007 (UTC)
 * Sorry for not signing--Stone 08:17, 7 November 2007 (UTC)

Possible solution re HIO4
From Dirac66: First for anyone trying to follow the previous section. According to the discussion history, the text at the left margin is by Ajrocke, and the indented text is insertions by Stone who forgot to sign.

Perhaps each of us is partly right. I proposed above (in the first HIO4 Example section) a text to clarify Stone's edit about HIO4, with information about Kolbe from Stone's answers to my questions. However this text is too long, and I forgot my own comment above that "The focus should remain on Kekule however since it is his article." Ajrocke says that a detailed discussion of HIO4 is not relevant to Kekule (who never discussed this molecule), and proposed that the paragraph be "deleted" - from this article? or from Wiki? He then says that the material would be valuable in another article, so I think that he meant deletion from this article only. But Stone's strong reaction suggests he thought total deletion from Wiki, as he agrees the paragraph can be moved to a better place.

So I think if we forget the word "delete", there is agreement that we can move the details about HIO4 to another article. However I would not like to see it just deleted with the idea that maybe someone in the future will put it in another article. Instead I think we should first identify together the most appropriate place to insert this information. If Kolbe raised the point about HIO4, it could be mentioned in the Conflicts section of his article. Except that I am uncertain on reading Ajrocke's comment as to whether he accepts that Kolbe in fact raised this point, so perhaps Stone and Ajrocke should first try to agree on whether it was Kolbe or someone else (I can not help here - I have no access to the original sources and very little German).

Another alternative would be a more general historical article, if possible one longer than the present article on structural theory.

After the information about HIO4 has been placed in another article, then we can eliminate its mention in the Kekule article. I suggest instead mentioning that Kekule's fixed valences work well in organic chemistry but less so in inorganic chemistry, with brief mention of the early criticism by Kolbe (or someone else) as well as of the later systematic clarification of the idea of valence by Werner (and also Lewis?). Dirac66 02:55, 7 November 2007 (UTC)


 * I totally agree! Although I always feel sad if something I contributed has to move!--Stone 08:17, 7 November 2007 (UTC)


 * I agree with Dirac66's solution to the issues discussed here. In response to his questions:  1.  When I used the word "delete" I meant "remove from this particular article", and did not mean to suggest "remove from Wikipedia".  Indeed, I tried to be clear that the paragraph would be good somewhere, just not in this biographical article.  2. I do not know whether Kolbe raised this particular issue, which is why I asked for a reference for his 1882 critique.  In preparing my biography of Kolbe (The Quiet Revolution: Hermann Kolbe and the Science of Organic Chemistry, University of California Press, 1993) I tried to read every article that Kolbe ever published, and every private letter he ever wrote.  Of course, one can never do that without missing something, and there is also the problem that with the passage of time one forgets this and that.  Ajrocke 13:41, 7 November 2007 (UTC)

benzene ring discovery (use later)
Citation



Abstract August Kekulé's account of his discovery of the ring or hexagonal structure of the benzene molecule--the event that ushered in the science of organic chemistry--is the single most cited personal report in psychological writings on creativity. Although his mental state has been depicted as dreaming, visual hallucination, alcoholic stupor, or hypnagogic imagery, such depictions do not cite Kekulé's original German account but rely either on secondary sources or an 1898 English translation by F. R. Japp in the "Journal of the Chemical Society." Kekulé's original account is presented together with the results of three new translations by German language experts. Comparative analysis of all translations indicates omissions in the one by Japp and significant differences. Psychological assessment indicates that Kekulé's breakthrough was due to specific forms of primarily conscious creative cognition named homospatial and janusian processes.

[I have downloaded the pdf and it is interesting. 69.228.171.150 (talk) 06:54, 18 November 2009 (UTC)]

Problem in the text concerning benzene
"with the two substituted carbon atoms separated by one, two and three carbon-carbon bonds"

I) Hydrogen is substituted not carbon so this needs clarification. II) Seems to me it would be clearer to talk about carbons instead of carbon-carbon bonds as in http://en.wikipedia.org/wiki/Arene_substitution_pattern where its said "In ortho-substitution, two substituents occupy positions next to each other". Then in meta there is one carbon inbetween and in para 2 carbons. 80.222.46.182 (talk) 17:52, 15 October 2013 (UTC)

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