Searching for CO returns methanol.

[PeterKraus]

What is the search string

>>> chemicals.identifiers.search_chemical("CO")
<ChemicalMetadata, name=methanol, formula=CH4O, smiles=CO, MW=32.0419>

Which chemical in the database do you believe should be found?

>>> chemicals.identifiers.search_chemical("carbon monoxide")
<ChemicalMetadata, name=carbon monoxide, formula=CO, smiles=[C-]#[O+], MW=28.0101>

Perhaps a toggle to prefer searching by formulas over smiles first should be added?

[CalebBell]

Hi Peter,
I always recommend strongly against searching by formula because formulas are NOT unique. If you really want to find a chemical by formula, you can do so as follows:

import chemicals
chemicals.identifiers.pubchem_db.search_formula('CO', autoload=True)

You will have to deal with potentially having a different chemical returned in the future though, although I'm not aware of another chemical with that formula in this case.

For example, C12H26 has 347 compounds in thermo.
Sincerely,
Caleb

[PeterKraus]

I completely understand the issues for higher alkanes etc. which have many isomers, and indeed there's no reasonable way of defining a cut-off.

I think it's worth considering whether the current priority of "formula after smiles" is a good one in general, especially given that one can already search by smiles explicitly using the smiles= prefix.

In my particular case (catalysis), nobody is going to call CO by the full name anywhere in their data tables. chemicals does a great job at disambiguating stuff like C3H6, propylene, propene to ensure it's the same molecule (smiles=CCC); however I'd argue that CO and methanol / MeOH should never both evaluate to smiles=CO as it's super unexpected (although technically correct).

Cheers!