The IUPAC name for this is ethylcyclobutane. I know that the formula is $\ce{C6H12}$.

I have no problems drawing the skeletal structure, but I have a little difficulty drawing the condensed structure. I know this is basic, but I just started learning how to name them.

I tried it below. For $\ce{CHCH2CH3}$, am I right to write it in a straight chain?



$\ce{CH3CH2CH(CH2)3}$ is the best you can do.

If you want to draw the cycle, then you should make it pendant, drwing a bond from the ring to the ethyl group.

enter image description here


There is no exact definition, what condensed formula means. One might be able to condense the formula up to the following

enter image description here

  • $\begingroup$ Is it possible to condense it like $\ce{(C4H7)C2H5}$ $\endgroup$ – Pritt says Reinstate Monica May 5 '17 at 8:47
  • $\begingroup$ @PrittBalagopal, (C₄H₇)C₂H₅ formula is not bad. It is not totally unambiguous, but other compounds it might mean, like "ethylbutene" would have different more appropriate condensed formula. $\endgroup$ – mykhal May 5 '17 at 8:57

TL; DR: In order to unambiguously denote both branching and cyclicity in a condensed structural formula, a linear formula should include a notation for connectivity, like such:

enter image description here

There is a special notation (external linker, like in mykhal's answer) for the bridging atoms with connectivities of three and higher in IUPAC's Nomenclature of Inorganic Chemistry [1, pp. 26–27]:

IR-2.3.4 Special bond indicators for line formulae

The structural symbols $\require{HTML} \style{display: inline-block; transform: rotate(90deg); font-size: 3em}{\Large ~~~[~~}$ and $\require{HTML} \style{display: inline-block; transform: rotate(-90deg); font-size: 3em}{\Large ~~[~~~~}$ may be used in line formulae to indicate bonds between non-adjacent atom symbols.


Examples 1-2

Examples 3-4

With this in mind, I'd like to propose the following condensed formula for ethylcyclobutane:

enter image description here

I used a dirty hack by utilizing a redox macros from the $\mathrm{\LaTeX}$ package chemformula without arrows which are supposed to denote electron flow:

        modules = {all},





  1. IUPAC “Red Book” Nomenclature of Inorganic Chemistry, 1st ed.; Connelly, N. G., Damhus, T., Hartshorn, R. M., Hutton, A. T., Eds.; IUPAC Recommendations; Royal Society of Chemistry: Cambridge, UK, 2005. ISBN 978-0-85404-438-2.

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