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How many different organic structures (from the pure theoretical viewpoint) are there with carbon and hydrogen atoms and atoms without hydrogen can be made with 5 carbon atoms only? Is there any way to count them all using Polya enumeration theory for "n" (hydro)carbonatoms? This is a follow up question from this Hydrocarbons with only 4 carbon atoms

riemannium
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  • ron was probably hooked to this earlier one, but for 4 C atoms it could be already considered too broad, and for 5 I wonder how it could be not. – Mithoron Oct 28 '17 at 20:05
  • I think it is not. Indeed, I was wondering about the mathematics behind the structure using chemical graph theory, and if...A mathematical formulation could be better....I mean, is there any known series for the number of structures with n-carbon atoms and hydrogen? – riemannium Oct 28 '17 at 20:11
  • Oh, you wanna calculate it not list them? There was quite a bit of such questions https://chemistry.stackexchange.com/search?q=is%3Aquestion+number+of+isomers – Mithoron Oct 28 '17 at 20:38
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    Isn't this fundamentally a maths question? – Beerhunter Oct 28 '17 at 20:56
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    This is simpler version of your question, then: https://chemistry.stackexchange.com/questions/16135/how-to-determine-number-of-structural-isomers – Mithoron Oct 28 '17 at 21:11
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    https://chemistry.stackexchange.com/questions/33356/is-there-a-formula-to-determine-the-total-number-of-constitutional-isomers – Mithoron Oct 28 '17 at 21:13
  • What makes this a bit difficult to calculate is that some theoretically possible compounds may be too unstable due to steric hindrance or bond strain. E.G. cyclopentane (C5H10) and cyclopentene (C5H8) are common industrial chemicals, 1.1.1-propellane (C5H6) exists, but is highly strained, and C5H5 is the cyclopentadienyl radical, not a stable molecule. – DrMoishe Pippik Oct 29 '17 at 01:38
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    BTW, spiropentadiene, or bowtiediene [no, I did not make up that name], C5H4, was first synthesized in 1991 and is highly unstable. – DrMoishe Pippik Oct 29 '17 at 01:50
  • I know those names, I will answer the question in a few weeks, I did it as exercise this summer but I want to see what manages people here... – riemannium Oct 29 '17 at 17:01

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