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Effects controlling the conformational selectivity and association parameters of H‐bonded assemblies between di‐ and triaminotriazines and bemegride
Author(s) -
Willner Itamar,
Rosengaus Jacqueline,
Eichen Yoav
Publication year - 1993
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610060106
Subject(s) - conformational isomerism , chemistry , intermolecular force , molecular mechanics , selectivity , stereochemistry , computational chemistry , crystallography , molecule , molecular dynamics , organic chemistry , catalysis
2,4,6‐Tris(aminocyclohexyl)triazine (1) and 2,4‐bis(aminocyclohexyl)‐6‐methoxytriazine (2) are present in solution in two and three equilibrating conformations, respectively. The activation barrier for interconversion of the conformers 1a ⇌ 1b is 14·55 ± 0·2 kcal mol −1 (1 kcal = 4·184 kJ) and the activation barrier for interconversion of the conformers 2a ⇌ 2b ⇌ 2c is 14·2 ± 0·2 kcal mol −1 . The conformational analyses of 1 and 2 were also followed by molecular mechanics calculations. Compounds 1 and 2 form H‐bonded intermolecular complexes with bemegride (3). Association of 3 proceeds by selection of a specific conformation of 1 and 2, i.e. 1b and 2a, respectively. The association constants of 3–1b and 3–2a are to K a = 915 and 450 l mol −1 , respectively. Molecular mechanics calculations for the H‐bonded intermolecular assemblies support the experimental observations of the selective conformational association.