Talk:Cyclopentadiene

odd name for a chemical compound??
Claims the chemical is odorless, but still whiffs suspiciously. Is this article for real? -- Cimon Avaro on a pogo stick 08:01 24 Jun 2003 (UTC)


 * It's not only real but correctly named.  jimfbleak 08:03 24 Jun 2003 (UTC)

merge with Dicyclopentadiene
The content at Dicyclopentadiene is mostly chemistry of cyclopentadiene anyway, so why not merge the pages. Pilatus 16:26, 6 September 2005 (UTC)
 * reasons not to merge: 22 articles that link to cyclopentadiene have no interest in Dicyclopentadiene and vice versa. I would prefer taking cyclopentadiene content out of dicyclopentadiene and place a cheminfobox in dicyclopentadiene with the chemical properties and the endo exo pics. V8rik 17:32, 6 September 2005 (UTC)
 * I was thinking of redirecting dicyclopentadiene to cyclopentadiene. Cyclopentadiene is exceedingly common whereas dicyclopentadiene is almost exclusively encountered in the context of cracking it to cyclopentadiene. That fact is incidentally mentioned in both articles. Pilatus 17:46, 6 September 2005 (UTC)
 * no clear majority for merge so I remove the notice. Pilatus already moved content not specific to dicyclopentadiene. Also, DCP has specific properties not found in cyclopentadiene such as endo/exo ismerism and reactivity in metathesis. V8rik 20:17, 14 October 2005 (UTC)
 * Support the non-merge, dicyclopentadiene is what you buy in a bottle, cyclopentadiene is the more commonly used but both have disting chemistry apart from the Diels-Alder reaction. Physchim62 (talk) 12:44, 20 November 2005 (UTC)
 * Support the non-merge, but I do agree that both pages need some work. Especially cyclopentadiene appears a bit ambiguous. --Dirk Beetstra 23:42, 30 April 2006 (UTC)

Rewrite
I have rewritten/resorted the page to a large extend. Added a section that asks for some organic chemistry (some specific Diels-Alder examples, with endo-exo info, and it's use as monomer in polymerisations), of which I know it is there, but I do not have the in depth info at hand. Please add.

I feel that the info about the use of the  eta should not be here, but in a seperate article, I think about moving it --Dirk Beetstra 00:10, 1 May 2006 (UTC)


 * Nice rewrite! DMacks 06:37, 1 May 2006 (UTC)

Rewrite 2 - cyclopentadiene and cyclopentadienyl
I have moved all information pertaining "cyclopentadienyl" (as the ligand used in organometallic chemistry) to Cyclopentadienyl complex. I suggest that this page evolves further as a description of the organic molecule, describing
 * physical properties,
 * it's synthesis,
 * reactivity
 * acidity (this can be linked with the page Pentamethylcyclopentadiene)

The page 'cyclopentadienyl' now redirects to 'cyclopentadienyl complex'.--Dirk Beetstra 20:36, 3 May 2006 (UTC)

Has anyone really seen the NMR of CpH?
We work with MeCpH, and the supposedly rapid sigmatropic thing alluded to in this report is not going on at all. So I am skeptical that CpH has a singlet in its H NMR spectrum. Me3SiCp, yes, but not CpH.--Smokefoot 04:11, 17 May 2006 (UTC)
 * I have seen 1H NMR spectra of CpH, but only at room temperature (the last time I encountered it, I think I recorded it on a 400 MHz). At that temperature and field, one sees different protons for the three different protons in the molecule.  I don't know what happens if you heat the tube up (well, dimerisation, but that is slow compared to recording NMR), I know cyclopentadiene is quite acidic, it might start to behave as [H+][C5H5-]. The 4. überarbeitete Auflage of my Hesse, Meyer, und Zeeh 'Spektroskopische Methoden in der organischen Chemie' gives for Cyclopentadien &delta; 2.90, 6.41 and 6.50 (page 179).  But I would not find it strange that the shifts are temperature dependent, so I would like to see a reference for that. --Dirk Beetstra 18:49, 17 May 2006 (UTC)

Molecular shape
The chembox says that the molecular shape of cyclopentadiene is "envelope structure". Is this really the case? Certainly cyclopentane has that shape as a primary conformation, but shouldn't cyclopentadiene be planar, or very nearly so? -- Ed (Edgar181) 20:11, 24 September 2008 (UTC)
 * might have info but I'm having trouble downloading the article right now. DMacks (talk) 20:26, 24 September 2008 (UTC)
 * Thanks! The article concludes "Geometry optimization of [cyclopentadiene] at the B3LYP level gave structures with planar five-membered rings of C2v symmetry".  I've corrected the article accordingly.    -- Ed (Edgar181) 20:33, 24 September 2008 (UTC)
 * Well, its not that simple. The 5 carbons are in the same plane, but the entire molecule is not planar.  The two hydrogens on the sp3 carbon are clearly not in the same plane as the carbons.  -- Jayron  32  15:07, 17 November 2009 (UTC)
 * in discussions like these only the carbon framework is considered V8rik (talk) 18:35, 17 November 2009 (UTC)

Synthesis of related compound
i need to know the preparation of pentacyanocyclopentadiene. it has a pKa value of -14. — Preceding unsigned comment added by 117.231.184.84 (talk) 03:37, 23 July 2012 (UTC)
 * US Patent 3853943 ("CYCLOPENTADIENES IN WHICH AT LEAST FOUR OF THE RING CARBONS CARRY CYANO SUBSTITUENTS AND METHODS FOR THEIR PREPARATION") looks like it has it (or at least various salts of it, which you could protonate if you wanted the neutral compound). The German wikipedia site has an article on this specific compound (de:Pentacyanocyclopentadien), but it does not describe the preparation of it. DMacks (talk) 08:24, 23 July 2012 (UTC)

dimerization reaction rates
Content on dimerization reaction rates was removed for dubious reasons. A kinetics section would be more than welcome. V8rik (talk) 20:31, 29 July 2015 (UTC)
 * Seeing raw kinetics data for a single reaction of a compound seemed too technical for the article about all facets of this compound. The table I removed addition to prose (that I did not remove) discussing its significance and analyzing the meanings of the values (akin to WP:SECONDARY). If someone wants data underlying the analysis of it, presumably the ref that is cited would have it. Is dimerization the only or most significant thing we have to say about this compound as a Diels–Alder diene? DMacks (talk) 19:39, 30 July 2015 (UTC)