I have searched all over the internet and I have found no specific answer. I just want to know if C4O5 is possible and what would it be called.

  • $\begingroup$ One could write many isomers with such formula. None would be realistic, most probably. $\endgroup$
    – Mithoron
    Commented May 21, 2020 at 22:43
  • 2
    $\begingroup$ +1 This seems like a reasonable question and has an interesting answer; I don't understand the aggressive down voting and insta-closing, or how that benefits the site. $\endgroup$
    – uhoh
    Commented May 22, 2020 at 2:55
  • 4
    $\begingroup$ Welcome to Stack Exchange @Liam, don't let this bother you. In the future you might add a little more detail to your question and when you say "I have searched... and have not found..." go ahead and include the results of what you did find and explain why it's not sufficient. Usually questions that show some effort are better received than those that don't show it. You may have searched hard but unless you include some evidence, some people will still assume (fairly or unfairly) that you haven't. $\endgroup$
    – uhoh
    Commented May 22, 2020 at 2:59
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    $\begingroup$ @uhoh Not my downvotes, but I guess the concern would be that without any other detail/context, this question could just as easily be "is $\ce{C_xO_y}$ possible?" or really even "is $\ce{X}$ possible" where $\ce{X}$ could be any compound that someone could possibly dream up. $\endgroup$
    – Tyberius
    Commented Jun 2, 2020 at 14:46
  • $\begingroup$ @Tyberius I'm not sure how that's going to be helpful to me, if you have some helpful advice for the OP it might be better to comment to them directly $\endgroup$
    – uhoh
    Commented Jun 2, 2020 at 14:53

2 Answers 2


Tetracarbon pentoxide, $\ce{C4O5}$, does not appear to be known, but Wikipedia reports what has become a surprisingly large variety of oxocarbons. They include simple carbon monoxide and carbon dioxide, various extended linear structures, single and multiple rings, oligomers and polymers, even fullerene oxides. Some are surprisingly stable: mellitic anhydride, $\ce{C_{12}O9}$, can be melted at 161°C, and the powerful pi acceptor $\ce{C_{10}O8}$ is stable in dry air up to 140°C.

  • 1
    $\begingroup$ C4O4 and C4O6 is known but not C4O5. $\endgroup$ Commented May 22, 2020 at 8:48
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    $\begingroup$ C5O5 too, but only in trace amounts. $\endgroup$ Commented May 22, 2020 at 9:51

$\ce{C4O5}$ can be found in a Chinese patent art(Ref. 1). It is called Oxolane-2,3,4,5-tetrone both in the patent and PubChem. In the patent, $\ce{C4O5}$ is shown as compound 2 and appears to be a compound which undergoes further reaction with itself eventually giving a desired product.

A google translation of the relative portion of the patent, from Chinese to English follows:

Route 1, the synthetic route is shown below, 2,3-dioxosuccinic acid (1) is heated in acetic anhydride solvent and passed through the ring reaction to obtain furan 2,3,4,5-tetraketone (2), compound (2) ) React with alkylamine in THF and thionyl chloride to obtain pyrrolidine-2,3,4,5-tetraketone (3) containing solubilizing alkyl chain[...]

Clearly, compound 2 was synthesized and it further reacted with itself. $\ce{C4O5}$, although obscure, does exist.

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  1. CN108976392 - "Conjugated polymer photoelectric material containing quinoxaline imide condensed ring and application thereof" (link)

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