Publication Date:
2015-12-23
Description:
Intermolecular and intramolecular non-bonding interactions play a crucial role in determining physical and biological properties of relevant amines, and we have recently reported that they are also responsible for changing mechanisms in aromatic nucleophilic substitution (ANS) involving amine nucleophiles, when they are carried out in solvents of low permittivity. The present work describes ANS in toluene with a series of biological amines that can set specific hydrogen bonding (H bonding) interactions due to their special molecular structures. Kinetic studies of ANS with 2-amino-5-guanidinopentanoic acid (arginine), (4-aminobutyl)guanidine (agmatine), 2,6-diaminohexanoic acid (lysine) and 3,4-dihydroxyphenethylamine (dopamine) towards 1-chloro-2,4-dinitrobenzene in toluene are reported. The kinetic results are compared with those obtained with 2-guanidinobenzimidazole and 2-(1H-imidazole-4-yl)ethanamine (histamine); both amines form intramolecular H bonds. The special types of H bonding were also investigated by ab initio density functional theory calculations, at the B3LYP/6-31++G(d,p) level, including counterpoise corrections to account for basis set superposition errors and solvent effects at the polarized continuum model level. Copyright © 2015 John Wiley & Sons, Ltd. Kinetic studies on aromatic nucleophilic substitution where the nucleophiles are amines that can set specific hydrogen bonding in toluene due to their special molecular structures are reported. An additional strong support to the dimer nucleophile mechanism is provided by the quantum chemical calculations on monomers and dimers that show that the calculated order in dimer stability is nicely correlated with kinetic results and strongly indicates that these studies are useful to enlighten the type of mechanism occurring in aprotic solvents.
Print ISSN:
0894-3230
Electronic ISSN:
1099-1395
Topics:
Chemistry and Pharmacology
,
Physics
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