Matched Pair
Definition: Substrate and chiral reagent/catalyst whose stereochemical preferences reinforce each other.
Context: Delivers higher selectivity than mismatched combinations.
Example: (S)-substrate with (S)-auxiliary.
Related Terms: Mismatched Pair, Double Stereodifferentiation.
Reference: Seebach, Angew. Chem. (1979).
Memory of Chirality
Definition: Retention of stereochemical information through achiral or planar intermediates via conformational constraints.
Context: Enables net stereospecificity where racemization might be expected.
Example: Acylium ion cyclizations retaining chirality.
Related Terms: Stereomutation, Enantiospecificity.
Reference: Houk, Angew. Chem. (2001).
Meso Compound
Definition: An achiral molecule with stereocenters and an internal plane/center of symmetry.
Context: No net optical activity, important in planning stereoselective routes.
Example: Meso-tartaric acid.
Related Terms: Symmetry, Diastereomer.
Reference: Eliel & Wilen (1994).
Meso-
Definition: A molecule containing stereocenters but overall achiral due to an internal plane or center of symmetry.
Context: Meso compounds are optically inactive even though they contain chiral atoms.
Example: Meso-tartaric acid.
Related Terms: Achiral; Symmetry; Diastereomer.
Reference: Eliel & Wilen (1994).
Misassignment of Configuration
Definition: The incorrect determination, description, or reporting of the absolute or relative stereochemical configuration of a molecule, stereogenic center, axis, or element.
Context: Misassignment of configuration can arise from incorrect application of CIP rules, misinterpretation of spectroscopic or crystallographic data, inappropriate use of chiroptical methods, or confusion between nomenclature systems (e.g., R/S vs D/L vs d/l). In pharmaceutical and medicinal chemistry, such errors can propagate through literature, patents, regulatory submissions, and clinical interpretation, leading to flawed structure-activity relationships, incorrect biological conclusions, or costly redevelopment.
Example: Assigning an alcohol as (R) based solely on optical rotation without corroborating evidence, later corrected by X-ray crystallography or VCD analysis showing the (S) configuration.
Related Terms: Absolute Configuration; Relative Configuration; CIP Rules; Stereochemical Assignment; Chiral Literacy; Stereo-Sloppy.
Reference: IUPAC. Compendium of Chemical Terminology (IUPAC Gold Book). 2nd Edition, 1997 (updated 2019).
Harada, N.; Nakanishi, K. Circular Dichroism Spectroscopy-Exciton Coupling in Organic Stereochemistry. Accounts of Chemical Research, 5, 257-263 (1972).
Mismatched Pair
Definition: Substrate and chiral reagent/catalyst with opposing preferences.
Context: Reduces stereoselectivity; addressed by switching catalyst or substrate.
Example: (S)-substrate with (R)-auxiliary.
Related Terms: Matched Pair, Stereoselectivity.
Reference: Evans, JACS (1981).
Molar Rotation (Φ)
Definition: Specific rotation multiplied by molar mass.
Context: Allows comparison of chiroptical responses across compounds.
Example: Molar rotation trends within homologous series.
Related Terms: Specific Rotation, Optical Activity.
Reference: Barron, Molecular Light Scattering (2004).
Molecular Imprinting
Definition: Template-directed polymerization producing cavities complementary to a target enantiomer.
Context: Creates synthetic receptors for separations and sensing.
Example: Imprinted polymers for S-propranolol.
Related Terms: Chiral Recognition, CSP.
Reference: Sellergren, Chem. Rev. (2000).
Mosher’s Method
Definition: Use of MTPA esters/amides to assign absolute configuration by Δδ patterns.
Context: Gold-standard for alcohols and amines in small-molecule analysis.
Example: Δδ analysis of secondary alcohols.
Related Terms: CDA, NMR.
Reference: Dale & Mosher, JACS (1973).