Study of aromatic nucleophilic substitution with amines on nitrothiophenes in room-temperature ionic liquids: are the different effects on the behavior of para-like and ortho-like isomers on going from conventional solvents to room-temperature ionic liquids related to solvation effects?
The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes (para-like isomers) with three different amines (pyrrolidine, piperidine, and morpholine) were studied in three room-temperature ionic liquids ([bmim][BF4], [bmim][PF6], and [bm(2)im][BF4], where bmim = 1-butyl-3-methylimidazolium and bm(2)im = 1-butyl-2,3-dimethylimidazolium). To calculate thermodynamic parameters, a useful instrument to gain information concerning reagent-solvent interactions, the reaction was carried out over the temperature range 293-313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration similar to that observed in methanol, suggesting a parallel behavior. The above reaction also was studied with 2-bromo-3-nitrothiophene, an ortho-like derivative able to give peculiar intramolecular interactions in the transition state, which are strongly affected by the reaction medium.
D'Anna
Francesca
F
Dipartimento di Chimica Organica E. Paterno, Università degli Studi di Palermo, Viale delle Scienze-Parco d'Orleans II, 90128 Palermo, Italy. fdanna@unipa.it
Frenna
Vincenzo
V
Noto
Renato
R
Pace
Vitalba
V
Spinelli
Domenico
D
D000588:Amines / Q000737:chemistry*; D001881:Borates / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D013696:Temperature; D013876:Thiophenes / Q000138:chemical synthesis / Q000737:chemistry*
C419324:1-butyl-3-methylimidazolium tetrafluoroborate; C520585:2-bromo-3-nitrothiophene; D000588:Amines; D001881:Borates; D007093:Imidazoles; D052578:Ionic Liquids; D012997:Solvents; D013876:Thiophenes