Вот ниже ссылка на дискуссию по карбинам и сразу за ней комментарий Сергея Евсюкова
http://cen.acs.org/articles/93/i46/Cont ... rbyne.html
Oh, no! Not again, not from the very beginning, please! Are we going to step on the same rake over and over again?
First of all, let’s agree about the terms once and for all. Firstly, carbyne, if it does exist, is not a wisp of non-interacting carbon chain-like molecules. Carbyne was and still is claimed to be a carbon allotrope, so it is supposed to be a material, as we know other allotropes like graphite or diamond. Secondly, the chain length within the crystal should be long enough to make the contribution of the end groups or atoms negligible. Thirdly, it should be stable enough at least to be isolated and explored. One can argue that transactinides existing for milliseconds are still considered as chemical elements. Nevertheless, we are talking about allotropes here, right? So let me make a couple of additional comments.
1. The existence of many hundreds of publications, dozens of filed inventions and re-filed re-inventions, as well as several books on carbyne (including one we published back in 1999), no matter how thick they are, does not provide any reliable and unambiguous evidence for the existence of carbyne, since all analytical methods used so far are either indirect or ambiguous. So I would suggest to keep considering carbyne a hypothetical allotrope until we finally will have seen a clear-cut x-ray single crystal analysis. (For more details see also my last outcry at this site:
http://cen.acs.org/articles/91/web/2013 ... erial.html )
2. Concerning the recent study by Yang et al. [1], I have got too many questions and cannot agree with many claims and interpretations made in the paper. Apparently, the Chinese group have synthesized very short and, therefore, soluble polyynes using a "novel" but well-known since a couple of decades method of laser ablation of carbon in a submerged electrical arc (see chapters by Tsuji et al., Wakabayashi et al., and Cataldo in the book Polyynes ed. by F. Cataldo, CRC Press, 2006). After that they managed to cast the solution onto a glass substrate, evaporate the solvent, and claim to have synthesized carbyne. The fact that the molecules are short is well-documented by their own mass-spectrometric data presented in the supplement (Fig.S6 (A)). The IR spectrum shown in Fig.2 triggers further questions. On the one hand long polyynes are known to be inactive in IR, and the peak shown in Fig.2B looks typically for short polyynes or even unsymmetrically substituted isolated triple bonds. On the other hand, why did the authors cut the spectrum off, having shown just a narrow range of 2000-2400 cm(-1)? I would like to take a look at the low- and high-frequency regions as well. I would also prefer to have data from classical elemental analysis rather than from EDX.
The authors also measured a 13C-NMR spectrum and wrote that "the chemical shift of the sp-hybridized carbon is in the range of 60 to 95 ppm". Yes, it is, but they reported their signals to lie in the range of 90-95 ppm, which is typical for isolated triple bonds, whereas conjugated polyynes are commonly known to resonate in a 55-70 ppm region [2-21].
The real advance of the study by Yang et al. seems to be the preparation of the crystalline stuff. The XRD and SAED definitely show a crystalline order, but the interpretation of nanorods based on "parallel arrays of helices" covered with gold clusters is rather curious. Having started with the known kinked-chain model postulated to stabilize carbon chains, the authors suddenly invoked the bending effect, which indeed is known from crystallographic studies of end-protected polyynes, and ended up with a new concept of wavy chains.
What is really puzzling in this study is the alleged stability of polyynes in the solid state. It has been proved many times (see for instance studies by Milany et al. [21, 22]) that unprotected carbon chains are extremely reactive and unstable (their collapse can be induced even by the electron beam during STEM measurements). The stability of crystals prepared by Yang et al. suggests either some special stabilization mechanism (gold atoms?) or just absence of carbon chains in the sample (cross-linking in the solid state, something like topochemical polymerization of diacetylenes).
Finally, the reasoning about ethanol as an ideal building block for carbyne, just because it has two carbon atoms in a "unique configuration" and thus provides a kind of a template for the formation of a triple bond, does not stand up under scrutiny. What about other diatomic molecules?
Summing up, one can conclude that structural evidence reported in the paper by Yang et al. can be called carbyne.
There are dozens of excellent synthetic studies by the research groups of Gladisz [3-7], Hirsch [8, 9], and Tykwinski [14-20], who developed exquisite syntheses of well-defined end-protected polyynes with up to 44 cabon atoms. Still, even longest molecules are just individual chemical substances, i.e. polyynes being far away from carbyne, and there are no examples of the successful transformation of organic polyynes into carbyne that could be proven with a clear-cut x-ray analysis.
Even if the authors will have provided clear structural evidence unambiguously confirming their samples to be crystalline polyynes, they still cannot be considered carbyne. In much the same way nobody calls naphthalene crystals graphite, and adamantane can hardly be called diamond.
P.S. The poetry above is almost lachrymatory cute…
REFERENCES:
[1] B. Pan, et al., Sci. Adv. 2015;1:e1500857; doi: 10.1126/sciadv.1500857.
[2] E. Kleinpeter, R. Borsdorf, 13C-NMR-Spektroskopie in der Organischen Chemie, Akademie, Berlin, 1981.
[3] H.-O. Kalinowski, S. Berger, S. Braun, 13C-NMR-Spektroskopie, G. Thieme, Stuttgart, 1984.
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[11] T.N. Hoheisel & H. Frauenrath, Org. Lett., 2008, 10 (20), 4525.
[12] A. Sarkar, et al., Macromolecules, 1998, 31 (17), 5624.
[13] M. Kijima, et al., Chem. Lett., 1999, (6), 531.
[14] R. Zeisberg & F. Bohlmann, Chem. Ber., 1974, 107 (12), 3800.
[15] S. Eisler, et al., J. Am. Chem. Soc., 2005, 127 (8), 2666.
[16] Th. Luu, et al., Org. Lett., 2005, 7 (1), 51.
[17] J. Kendall, et al., Org. Lett., 2008, 10 (11), 2163.
[18] W.A. Chalifoux & R.R. Tykwinski, Compt. Rend. Chim., 2009, 12 (3-4), 341.
[19] W.A. Chalifoux, et al., Angew. Chem., Int. Edition, 2009, 48 (42), 7915.
[20] R.R. Tykwinski, et al., Pure Appl. Chem., 2010, 82 (4), 891.
[21] W.A. Chalifoux & R.R. Tykwinski, Nature Chem., 2010, 2 (11), 967.
[22] L. Ravagnan, et al., Chem. Commun., 2011, 47 (10), 2952.
[23] C.S. Casari, et al.: Carbon, 2004, 42 (5-6), 1103.
Чтобы не добавлять тут еще лишнего текста вот здесь продолжение подобной дискуссии с ответом Сергея Евсюкова
http://cen.acs.org/articles/91/web/2013 ... erial.html
нет у человека большего врага, чем он сам.