Details:
A reagent can have multiple CAS numbers. PubChem link might not work with some CAS Number giving the error message “The system has been unable to retrieve a link to PubChem.”.
Reason 1:
For E.g.: if user uses CAS number 7786-30-3 for Magnesium Chloride as Reagent, PubChem link will not work. This happens because Signals Notebook search checks in Depositor-Supplied Synonyms in PubChem website (https://pubchem.ncbi.nlm.nih.gov/compound/5360315). The CAS number 7786-30-3 is not listed in it.
Solution will be to use a CAS number listed in the Depositor-Supplied Synonyms. Here using CAS number 17638-61-8 will resolve the issue.
Reason 2:
PubChem database has more than one chemical with the same CAS number. In this case also PubChem link will not work as there are multiple entries for a single CAS number.