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I saw a little chemistry pun with a couple of hydrocarbons included, and it had me thinking if they were actually possible and if so, what would the name given to it be.

The hydrocarbon I am curious about:

The hydrocarbon I am curious about.

For those wondering what the pun is:

enter image description here

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  • $\begingroup$ What do you think about their names? $\endgroup$ – manshu May 15 '16 at 19:59
  • $\begingroup$ What do you mean? $\endgroup$ – Finian May 15 '16 at 20:01
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    $\begingroup$ I mean do you have any idea about their names? Do you know IUPAC naming? These kinds of questions needs some opinion of OP, so that the answerer can clear his confusion. $\endgroup$ – manshu May 15 '16 at 20:05
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    $\begingroup$ Nice joke :) Both hydrocarbons are OK, however this exam would need to have quite hard on reactions ;) $\endgroup$ – Mithoron May 15 '16 at 20:08
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    $\begingroup$ I know about naming alkenes (E.g but-1,2-diene) and cyclic hydrocarbons (E.g cyclohexane) but I have never seen a hydrocarbon with either a double bonded alkyl group, so I'm mainly wondering what having an alkyl group but with double bonds does to the name. If I were to guess I would say the hydrocarbon would be 1-butylecyclohexane. $\endgroup$ – Finian May 15 '16 at 20:11
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If you want to consider the diene as the main chain, you could call this 2-cyclohexyl-1,3-butadiene. This used to be the proper name for the compound, as double bonds used to take priority over any length of a carbon chain in IUPAC nomenclature. This compound exists, and you could theoretically purchase it at some place like this. In recent years, the proper priorities for IUPAC have changed. Now, the longer chain takes priority over double bonds, and thus this compound should be referred to using the cyclohexane as the main chain. This means that the compound should be called (buta-1,3-dien-2-yl)cyclohexane. For all practical purposes, either name should work, as they both describe the same molecule; however, the second name is consistent with IUPAC standards.

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    $\begingroup$ Please note that double bonds do not always have priority since the IUPAC recommendations have been changed. In the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the first criterion to be considered in choosing a preferred parent acyclic chain is the length of the chain; unsaturation is now the second criterion. $\endgroup$ – Loong May 15 '16 at 22:02
  • $\begingroup$ Would you then use methenyl as a substituent name? I don't think a double bonded carbon can be treated as a side chain when one of the sp2 carbons is part of the parent chain. Please correct me if I am wrong. $\endgroup$ – Niels Kornerup May 15 '16 at 22:49
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    $\begingroup$ In general nomenclature, the name 2-cyclohexylbuta-1,3-diene may be used so that the unsaturated acyclic structure may be recognized (see Subsection P-44.1.2.2); however, the ring is preferred to the chain when constructing the preferred IUPAC name (buta-1,3-dien-2-yl)cyclohexane (see Subsection 52.2.8). $\endgroup$ – Loong May 16 '16 at 10:08
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The after-exam molecule is simply referred to as:

2-cyclohexylbutadiene in Iron catalyzed 1,4-hydroboration of 1,3-dienes Journal of the American Chemical Society 131(36): 12915–12917,

and even more simply:

cyclohexylbutadiene in Intermolecular Hydroamination of 1,3-Dienes Catalyzed by Bis(phosphine)carbodicarbene−Rhodium Complexes J. Am. Chem. Soc., 2014, 136 (17), pp 6227–6230

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2-cyclohexyl-1,3-butadiene. (after the exam)

[1,1,2-trimethylpropyl]cyclohexane (before the exam)

There are variants of these names, like locant numbers unnecessarily placed between prefix and infixes. There are trivial and substitutive names but these are more appropriate and clear.

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