“Decoding the rules: how chemists name and navigate molecular twists.” Introduction Correctly describing the stereochemistry of a molecule is as important as understanding it. In this part, we focus on the Cahn–Ingold–Prelog (CIP) system, which provides the rules for unambiguous assignment of absolute configuration at stereocenters (R/S) and for double bond geometry (E/Z) system. We …
Stereochemistry, the study of spatial arrangements of atoms in molecules, demands a precise and universally accepted nomenclature system. Unlike simple chemical formulas, which only indicate connectivity, stereochemical nomenclature conveys three-dimensional information essential for understanding molecular behavior, biological interactions, and pharmaceutical effects. Several systems have been developed to capture these subtle but critical differences. 🔬✨ Stereochemical …
Mapping Stereochemical Nomenclature: A Chiralpedia Guide Read More »
“Pharmacological studies confirm the high activity of triprolidine and the superiority of (E) over corresponding (Z) isomers as H, antagonist” ( Ref: – – – from “Wilson and Gisvold’s Textbook of organic medicinal and pharmaceutical chemistry, 2010”). “Triprolidine is 2-[(E)-1-(4-methylphenyl)-3-pyrrolidin-1-ylprop-1-enyl]pyridine”, the IUPAC name. To understand the above statements one need to be familiar with the …
“If you immediately identified this as a molecule with an internal plane of symmetry (and hence an achiral molecule, incapable of having an enantiomer), congratulations. If not, you just fell into The Meso Trap”. Source: https://www.masterorganicchemistry.com/2011/01/12/the-meso-trap/ The meso concept is a common aspect in examinations and tests to evaluate how good you understand the concept of chirality So let us …
“Chloramphenicol possesses two chiral carbon atoms in the acylamidopropanediol chain. Biological activity resides almost exclusively in the D-threo-, isomer: the L-threo–and the D– and L-erythro– isomers are virtually inactive.” – – – from “Wilson and Gisvold’s Textbook of organic medicinal and pharmaceutical chemistry”. In the name “D-threo– and L-threo-Chloramphenicol”, what does the prefix threo– and …
Erythro- and Threo- prefixes: the (same-) or (opposite-) side? Read More »
Atropisomers are stereoisomers resulting from hindered rotation about single bonds where the steric strain barrier to rotation is high enough to allow for the separation of the conformers. Note: Butane, for example, has conformations that are atropisomers; however, unlike the biaryls, the barrier to rotation is so small that they are interconverted rapidly at room …
Atropisomers: things are tight, single bond won’t rotate Read More »
The Fischer convention was introduced to specify the configuration of a stereogenic center and uses the symbols D and L. The use of capital letters is to differentiate from the “d” / “l” notation (optical descriptor) described earlier. This nomenclature system has become obsolete. In general the D/L system of nomenclature is superseded by the Cahn-Ingold-Prelog (CIP) rule to describe …
D-/L- system naming: the (left-) or (right-) hand side? Read More »
One of the major problems in organic chemistry is the representation of three-dimensional structures in a two-dimensional media (viz. sheet of paper, blackboard, etc.). Chemists sometimes represent structures for chiral molecules with two-dimensional formulas called Fischer projection formulas. These two-dimensional formulas are a quick way to show three dimensions without the hassle of having to …
Fischer Projection: hassle free way to depict a stereoformula in 2D projection Read More »
Enantiomers are pair of molecules that exist in two forms that are mirror images of one another but cannot be superimposed one upon the other. They are also referred to by chemists as chiral twins or handed molecules. Each twin is called an enantiomer. Naming of enantiomers is important to understand ‘which structure refers to which enantiomer?’. The chirality …
Naming enantiomers: the left-(or right-) handed? Read More »