Chemical Structure Sketcher to Canonical SMILES Online
Start from the imatinib parent structure, inspect its canonical representation and open the structure editor to explore changes. The same molecular graph drives the depiction, identifiers and descriptor calculations. The preloaded structure is a cited reference compound; editing it creates a new input whose identity and properties must be considered separately.
The existing shipped imatinib example uses the ChEMBL941 parent SMILES. It does not represent every salt, formulation or protonation state sold under the drug name. The active graph, rather than the example label alone, defines the calculation.
Move between a drawing and a molecular graph
A chemical drawing is a view of atoms, bonds and stereochemical declarations. A SMILES string is another representation of that information, not a picture and not a compound name. When an edit changes the graph, the workspace recalculates the linked properties. Check that the intended bond order, aromatic system, formal charge and isotope labels survived the edit before interpreting the numerical readout.
Imatinib provides several connected ring systems and functional groups without requiring an unusually large structure. It is useful for observing how the editor, canonical text and descriptor panel remain linked. The precomputed example can be inspected before the full chemistry engine is needed; analysing a new input loads the existing engine on demand. This loading distinction does not change what the example structure represents.
Keep identifiers tied to the represented chemical form
A structure string can distinguish a charged form or a specific stereoisomer that a casual drug name does not. Standard InChI also applies its own normalisation conventions, so identifier equality has defined limits. Preserve the original submitted representation when the form matters to a calculation or experiment, and record any standardisation that occurred before comparing compounds.
For downstream experiments, link the structure to a sample record that states salt, purity, batch and storage history. Those facts are not recoverable from a drawing alone. An identifier is useful for joining records, while the actual material used may have additional composition or formulation information. The stock-preparation workflow therefore asks for an explicit formula-weight basis rather than assuming that the parent example is the vial contents.
Equations and variables
Average molecular weight
MW = Σ ni Mi
- ni
- Count of atoms of element i in the represented structure
- Mi
- Average atomic mass used by the engine (g/mol)
- MW
- Molar mass of the represented structure (g/mol)
Formal charge accounting
Q = Σ qi
- qi
- Formal charge assigned to atom i in the drawn representation
- Q
- Net formal charge of that representation
Scope and limitations
- Canonical SMILES is canonical for a particular toolkit and configuration; different valid strings can encode the same graph.
- Unspecified stereochemistry, tautomer choice, disconnected salts and formal charge can change identifiers or descriptor interpretation.
- The structure editor and descriptor engine have different input-size limits. A valid analysis does not imply that every large structure can be conveniently edited.
Sources and provenance
- ChEMBL 37 parent structures in the shipped compound libraryCC BY-SA 3.0; share-alike
Existing library capture: 28 September 2026. Preserve attribution when redistributing its rows.
- RDKit descriptor implementation and versioned reference checksBSD-3-Clause
Method implementation; computed molecular properties are estimates.
- InChI: the IUPAC International Chemical IdentifierMIT for the shipped InChI software; source-specific website terms
Technical questions
Why does the canonical SMILES change after I draw the same molecule?
Canonicalisation chooses one deterministic traversal for a graph within the toolkit. Atom ordering in the original string need not be preserved. Compare graph identity, stereochemical information and the identifier semantics rather than treating a changed text order as evidence that the chemistry changed.
Does the imatinib example include mesylate?
The reference is the ChEMBL parent structure. A vial salt or hydrate may have a different formula weight from that parent. When preparing a stock, use the form and purity documented on the vial or certificate rather than borrowing the parent molecular weight without checking.
Can a SMILES specify all stereochemistry?
It can encode defined stereochemical information for supported structures, but missing annotations remain missing. A plausible two-dimensional drawing is not evidence of absolute configuration. Inspect stereocentres and bond geometry explicitly, especially after importing or editing a structure.
Connected workflows
- DMSO stock reconstitution volume
Use the actual vial form when converting mass into stock volume.
- TPSA and Crippen logP calculation
Inspect graph-derived polarity and lipophilicity descriptors.
- 4PL IC50 curve fitting
Keep a structure identity alongside its experimental response.
- PAINS Filter and Substructure Alert Screening Inspector
Screen a drawn structure for PAINS substructure alerts.