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Titolo:
Hydrogen-bonded complexes of pentaalkyl guanidines
Autore:
Rappo-Abiuso, M; Llauro, MF; Chevalier, Y; Le Perchec, P;
Indirizzi:
Univ Savoie, UMR 5041 CNRS, Lab Mat Organ Proprietes Specif, F-69390 Vernaison, France Univ Savoie Vernaison France F-69390 s Specif, F-69390 Vernaison, France CNRS, Serv RMN, Federat Rech Polymeristes Lyonnais, FR 2151,LMOPS, F-69390Vernaison, France CNRS Vernaison France F-69390 s, FR 2151,LMOPS, F-69390Vernaison, France
Titolo Testata:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
fascicolo: 1, volume: 3, anno: 2001,
pagine: 99 - 106
SICI:
1463-9076(2001)3:1<99:HCOPG>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
BASES; ARENESULFONATE; EQUILIBRIUM; RECOGNITION; CONSTANTS; CHLORIDE; SERIES; DESIGN; FTIR; IR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
61
Recensione:
Indirizzi per estratti:
Indirizzo: Le Perchec, P Univ Savoie, UMR 5041 CNRS, Lab Mat Organ Proprietes Specif,BP 24, F-69390 Vernaison, France Univ Savoie BP 24 Vernaison France F-69390 ernaison, France
Citazione:
M. Rappo-Abiuso et al., "Hydrogen-bonded complexes of pentaalkyl guanidines", PHYS CHEM P, 3(1), 2001, pp. 99-106

Abstract

The hydrogen-bonded complexes of strongly basic pentaalkylguanidines (G) with 4-fluorophenol as a proton donor reference (FP) have been studied in CDCl3 solution by means of C-13 NMR spectroscopy. The equilibrium constants for formation and the chemical shifts of all the C-13 NMR lines of the hydrogen-bonded complexes were determined. This rich spectroscopic characterization of the complexes allowed us to discuss their structure. The guanidines were found to be more basic than triethylamine, the bicyclic ones being thestrongest bases, in accordance with expectations. The ion pair character of the hydrogen-bonded complexes was as high as 40% for the strongest bases. In addition to the expected GFP complex, a diassociation complex G(FP)(2) was observed at high fluorophenol concentrations. In this latter complex, one fluorophenol molecule is ionized by full proton transfer to the guanidine and the second fluorophenol molecule is bound by hydrogen bonding to the fluorophenate anion. A linear relationship between the C-13 NMR chemical shift variations of 4-fluorophenol and log(K-1) was found, as in the originalwork of Gurka and Taft using F-19 NMR.

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Documento generato il 31/03/20 alle ore 18:51:26