Figure 2 : Examples of PubChem entries with charged chemical formulas.

From: Automated evaluation of consistency within the PubChem Compound database

Figure 2

(a) PubChem CID 91929631. The archived chemical formula for this entry in PubChem is C15H17N4O3S+. This formula indicates 17 hydrogen atoms in the positively charged compound. However, the core parent structure of this compound contains only 16 hydrogen atoms; the additional hydrogen results from protonation of the compound in its charged form. The ALATIS formula for this compound “C15H16N4O3S” shows the correct atom composition with 16 hydrogen atoms, and the additional hydrogen is indicated in the corresponding InChI string (layer “/p”) “InChI = 1 S/C15H16N4O3S/c16-15(17)11-5-4-8-13(9-11)23(21,22)18-10-14(20)19-12-6-2-1-3-7-12/h1-9,18 H,10H2,(H3,16,17)(H,19,20)/p + 1” [http://alatis.nmrfam.wisc.edu/pubchem/91929631]. (b) PubChem CID 91124997. The chemical formula for this compound in PubChem is (C15H16N+). In this case, the positive charge arises from the quaternary nitrogen, and the correct composition of the compound contains 16 hydrogen atoms, which matches the formula in PubChem. The ALATIS formula for this compound shows the 16 hydrogen atoms (C15H16N), and the charge is represented by layer (“/q”) in the corresponding standard InChI string “InChI = 1 S/C15H16N/c1-11-6-5-9-15-14-8-4-3-7-13(14)10-12(2)16(11)15/h3-9,12 H,10H2,1-2H3/q + 1/t12-/m0/s1” [http://alatis.nmrfam.wisc.edu/pubchem/91124997].