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Valences for Sulfur, Phosphorus and Nitrogen

In light of the posting by Oliver Fiehn’s group (http://fiehnlab.ucdavis.edu/projects/Seven_Golden_Rules/Ring-Double-Bonds/), I’ve decided to blog some compounds I’ve encountered in the lab. Using the 2nd formula from the previous blog (http://acdlabs.typepad.com/elucidation/2008/03/rings-double-bo.html), for some cases the RDBE calculation will work if the correct atom valence is known.

Note: the nitrochloroform compound can be drawn more than one way and thus the observed RDBE can be either 1 or 2.

Rdbe_n_p_s_4

Elucidating a structure containing sulfur can be tricky sometimes. My approach is to consider the likely valences starting with S(II) first, then S(IV), and finally S(VI). If I have prior knowledge of the starting material or a derivative(s), I would start with that valence. If multiple O atoms are present in the Molecular Formula and the NMR data shows no OH groups, then I might favour starting with a S(IV) first.

TIP: The best approach is to cover all your bases to avoid missing something. I strongly recommend trying all valences for P, N and S, thus ruling out any other possible structure that might have otherwise been overlooked.