Kendrick Mass Defect Explorer

Give it a list of neutral monoisotopic masses with one value per feature. Set a scalar and any homologous series spaced by that repeat unit flattens into a horizontal row.

KM = neutral mass × scalar · KMD = KM − floor(KM) · scalar = nominal / exact mass of the repeat unit

Deconvolute adducts first. [M+H]⁺, [M−H]⁻, [M+Na]⁺ and multiply charged ions must be converted to neutral monoisotopic mass before loading — nothing here converts them for you.

Data

Neutral monoisotopic mass

Value column (optional)

Paste straight from a spreadsheet. A header row is ignored. Two columns pasted into the first box also work.

Scalar Repeat units from the literature

Max atoms in the repeat unit

12 suits CH2 / CF2 / H2O. Raise it for bigger units — C5H8 needs 13, C6H10O5 needs 21.

Encode value as

Minimum value

KMD plot

Scalar → repeat unit

Every C_0-10H_0-20N_0-5O_0-5F_0-20P_0-3S_0-6 composition within the atom cap and passing Senior's third rule, scored by |nominal/exact − scalar|, closest first. The H/C, N/C, O/C, P/C and S/C columns are reported but not filtered on — those windows describe whole molecules, and a repeat unit like CF₂ fails H/C simply for having no hydrogen.

Senior's third rule passes when Σvalence − 2(atoms − 1) ≥ 0; DBE = (2C + N − H − F) / 2; ratio windows are H/C 0.2–3.1, N/C ≤ 1.3, O/C ≤ 1.2, P/C ≤ 0.3, S/C ≤ 0.8. Values are mapped on a log₁₀ scale when they span more than two orders of magnitude — the legend says which. Scalars are listed to 8 decimal places: at only 6 the truncation error is larger than the gap between neighbouring compositions, so the lookup misses the unit you meant.