Descriptor (chemistry)
In chemical nomenclature, a descriptor is a notational prefix placed before the systematic substance name, which describes the configuration or the stereochemistry of the molecule.See: cis–trans isomerism The descriptors cis (Latin, on this side of)[2] and trans (Latin, over, beyond)[3] are used in various contexts for the description of chemical configurations:[4][5] In organic structural chemistry, the configuration of a double bond can be described with cis and trans, in case it has a simple substitution pattern with only two residues.The position of two residues relative to one another at different points in a ring system or a larger molecule can also be described with cis and trans if the structure's configuration is rigid and does not allow simple inversion.These are usually two independent single substituents, but in case of fused ring systems, ortho-fusing is also mentioned unless the substitution pattern is regarded in the name like in [2.2]paracyclophane.The use of syn and anti to indicate the configuration of double bonds is nowadays obsolete, especially in case of aldoximes and hydrazones derived from aldehydes.The terms fac (from Latin facies, 'external face')[16] and mer (from 'meridional')[17] can specify the arrangement of three identical ligands around the central atom in octahedral complexes.[18][19] The prefix fac describes the situation when the three identical ligands occupy the three vertices of an octahedron triangular surface.While n, iso and neo are written in small and italic letters, for cyclo this is only the case in inorganic compounds.[25] In organic compounds, "cyclo" is frequently used as a name component, not separated by a hyphen and also considered in alphabetical sorting.[31] The term catena (Latin: "chain") is used in the inorganic nomenclature[32] to describe linear, chain-like polymers from identical polyatomic units.Typographically, (R) and (S) are placed in uppercase and italic; the frequently preceding locants, the enclosing round brackets and the commas, on the other hand, as normal.
chemical nomenclaturesystematic substance namestereochemistrymoleculepublicationslocantschemical structurecis–trans isomerismmaleic acidfumaric acidorganic structural chemistrydouble bondcomplex chemistryoctahedral complexessquare planar complexescisplatinE-Z notationViolet leaf aldehydealkenescumulenesoximesheteroatomssubstitutedring systemsArene substitution patterno-Cresolm-Cresolp-Cresolbenzene ring[2.2]paracyclophane1,2-dimethylbenzeneEndo-exo isomerismSyn and anti additionhydrazonesaldehydesAldoximesneomentholmentholabietic acidn-pentaneIsopentaneNeopentanecyclopentaneSecondary (chemistry)Tertiary (chemistry)n-Butanolsec-Butanoltert-ButanolSpiro compoundcatenanesstereospecific numberingCahn–Ingold–Prelog priority rulesnorephedrineTropinemeso compoundshydroxyl groupFischer projectionglucosedextrorotatorylevorotatoryoptical rotationWayback MachineActa Crystallogr.ChiralityRacemic mixtureConfiguration descriptorsE–Z notationSecondarytertiaryCatenaneAbsolute configurationsCIP (Cahn–Ingold–Prelog) priority rules