Check whether a structure is consistent with a spectrum. Give a SMILES and an MS/MS (paste peaks, drop a file, or reference a USI): the app verifies the neutral mass + adduct against the observed precursor, and annotates product-ion peaks by systematic bond-breaking. Your structure never leaves your browser — only a USI, if you give one, is resolved via GNPS2.
| Adduct | Theoretical m/z | Δ (mDa) | Δ (ppm) |
|---|
| m/z | Intensity | Fragment | Δ (mDa) | ppm | H shift | Bonds cut |
|---|
Fragment annotation breaks all combinations of up to two heavy-atom bonds and matches each connected substructure's monoisotopic mass (allowing ±2 H rearrangement) to product ions of charge 1. A match is plausibility, not proof — a formula can fit by coincidence, and true fragmentation may involve rearrangements this simple model misses. Implicit hydrogens are inferred from a Kekulé valence model, which can be off for exotic hypervalent centers. Precursor mass uses RDKit's exact mass. Nothing here is uploaded except a USI you supply.