As would-be elucidators dive into an elucidation for an organic unknown, narrowing down a single molecular formula (MF) becomes vital in simplifying the elucidation. However, one hurdle quickly leads into another. As the total atom count adds up, the number of possible isomers increases just as much (See Table and Graph below).
I can’t imagine drawing by hand every possible isomer for C12H26 at 355. And even if I did, how would I determine the candidate structure? The only choice is to acquire additional data to help eliminate the poor candidates. In my experience, the best choices are 1D and 2D NMR, MSn, and/or single-crystal XRD data.
MF Number of Isomers