How many alkanes of molecular weight $M$ are chiral?

As a particular case let us consider M=100.The general formula for such a alkane is $C_nH_{2n+2}$ where $n$ is the number of carbon atoms.

Putting in values of molecular weight we get $12n+2n+2=100$ which gives $n=7$. So there are 7 carbon atoms. So far I could think of the following two structures.


Since their enantiomers are also chiral giving us a total of 4 chiral alkanes. However I am interested in the general case when the molecular weight is given M. Is there some generalised result to the situation?

  • $\begingroup$ No, there isn't. You could only try to get max number, not accounting for steric factor. $\endgroup$
    – Mithoron
    Jan 1, 2017 at 18:27
  • 1
    $\begingroup$ check out chemistry.stackexchange.com/questions/16135/… $\endgroup$
    – Mithoron
    Jan 1, 2017 at 18:37
  • $\begingroup$ The first problem to solve would be the one in the question Mithoron linked. If you got that solved, you can start figuring out which one of the actually synthesisable compounds can or cannot be chiral. It’s very non-trivial. $\endgroup$
    – Jan
    Jan 1, 2017 at 20:59


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