This code system http://hl7.org/fhir/substance-stereochemistry defines the following codes:

CodeDisplay
ConstitutionalIsomer constitutional isomer
Stereoisomer stereoisomer
Enantiomer enantiomer
<status value="draft"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="The stereochemistry type of a substance."/><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/substance-stereochemistry"/><content value="complete"/><concept><code value="ConstitutionalIsomer"/><display value="constitutional isomer"/></concept><concept><code value="Stereoisomer"/><display value="stereoisomer"/></concept><concept><code value="Enantiomer"/><display value="enantiomer"/></concept></CodeSystem>