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The dissociation constants of diprotonated chalcogenobispyridines: Transmission of electronic effects across chalcogen bridges
Author(s) -
AngusDunne Sarah J.,
Dunne Simon J.
Publication year - 2011
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.651
Subject(s) - chemistry , chalcogen , steric effects , delocalized electron , electronegativity , deprotonation , computational chemistry , valence (chemistry) , crystallography , stereochemistry , photochemistry , organic chemistry , ion
The dissociation constants of the diprotonated chalcogenobispyridines have been determined using potentiometric titrations to establish a method for the measurement of the ability of a bridging ligand to relay electronic effects. The relationship between p K a and structure of the chalcogenobispyridines results from a balance between inductive, mesomeric, and steric effects. Delocalization of cationic charge onto the bridgehead increases the apparent electronegativity of the bridging atom, thereby relaying a strong base‐weakening effect to the site of first deprotonation. Such delocalization was found to be a function of both the substitution site (4‐X > 2‐X ≫ 3‐X) and orbital overlap requirements (S > O ≈ Se > Te). J. Heterocyclic Chem., (2011).